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The effects of different copper (and some other) catalysts on the conversion of triphenyl- and tetraphenyl- diazocyclopentadienes and of some phenyliodonium αα′-dicarbonylylides into arsonium and other ylides
Tetrahedron Vol. 38. No. 22, PP. 3355 lo 3358, 1982 Printed in Great Britain.
kW~-4O20/82/223355-04$03.~/0 @I 1982 Perganos Press Ltd.
THE EFFECTS OF DIFFERENT COPPER (AND SOME OTHER) CATALYSTS ON THE CONVERSION OF TRIPHENYLAND TETRAPHENYL-DIAZOCYCLOPENTADIENES AND OF SOME PHENYLIODONIUM cd-DICARBONYLYLIDES INTO ARSONIUM AND OTHER YLIDES J. NICHOLASC. HOOD, DOUGLASLLOYD,* WILLIAM A. MACDONALD and T. MAURICESHEPHERD Departmentof Chemistry, Purdie Building,The University of St. Andrews, St. Andrews, Fife KY16 9ST, Scotland (Received in the U.K. 8 February 1982)
Abstract-Diaio-compounds or iodonium ylides may be converted into arsonium and other ylides when heated in solution with triphenylarsineor other suitable carbene (or carbenoid) acceptor, and with a suitable Cu derivative present. The effects of using diierent copper complexes and salts are described and discussed. Other metal derivativeswere for the most part ineffective as catalysts.
Two established methods for the formation of arsonium ylides are by heating either “stable” diazo-compounds’-3 or iodonium ylides4 in the presence of an arsine, commonly triphenylarsine. Ylides other than arsonium have been made similarly. Reaction is assumed to involve dissociation of the diazo-compound or iodonium ylide to provide a carbene which is at once trapped by the arsine present. In both cases reaction is frequently improved by the presence of Cu-bronze or Cu compounds and some such reactions have been shown to take place only in the presence of a Cu-catalyst?-’ It has been suggested that Cu-catalysed decomposition of both diazo-compounds6 and iodonium ylide$ may involve initial formation of a complex with the Cu derivative. Little attention has been paid to the effects on ylide formation of varying the Cu-catalyst and the present account records some findiis in this direction. Conversion of diazo-compounds ylides
into arsonium and other
Triphenylarsonium ylides can be prepared by heating mixtures of triphenylarsine and so-called “stable” diazocompounds, in which the diazo group is attached to a cyclopentadiene ring or to a C atom which also bears electron-withdrawing groups. Nearly always the yield of ylide obtained is improved by the presence of a Cucatalyst and in some cases no ylide is obtained in the absence of such a catalyst.“’ Furthermore the use of a catalyst enables the reaction to be carried out at a markedly lower temperature and in solution.’ For example reaction of diazo-2,3,4-triphenylcyclopentadiene (1) with triphenylarsine in the presence of Cu-bronze gave similar yields (-55%) of the ylide (2) whether the reaction was carried out in refluxing benzene, cyclohexane or ethanol.’ In the absence of solvent and catalyst a temperature of 150” was required for reaction to ensue and the yield was only -M?. In solution, as without solvent, a certain minimum temperature seems to be required to bring about reaction. For instance diazo-compound (1) was not converted into ylide (2) in the presence of Cu-bronze in methanol or petrol (b.p. 40-60’) as solvents. Bis(acetylacetonato)copper(II) has had wide use as a Cu-catalyst soluble in organic solvents, and with (1) and
Ph
Ph Ph
Ph
Ph&
N2
AsPh,
w
cat. heat
Ph
Ph
2
1
triphenylarsine in boiling benzene provided an 85% yield of ylide (2). Use of the Cu(II) complexes of other simple p-diketones, e.g. 3-methylacetylacetone, benzoylacetone or dibenzoylmethane, provided similar yields (90, %, 85%), but with the more sterically hindered complex of dipivaloylmethane a somewhat lower yield (67%) was obtained. Steric factors may be hindering the reaction in this case since from the more crowded diazotetraphenylcyclopentadiene (3) under the same conditions, use of the acetylacetone or dipivaloylmethane derivatives of Cu provided, respectively, yields of only 45% and 30%. Replacement of one of the 0 atoms of a /3-diketone by a N atom as in (4), also provided an efficient catalyst, producing a high yield (!W%) of ylide (2), but the bisazaderivative (5) gave a much lower yield under standard conditions (2h; 30%). It may be inferred that steric factors are causing this lowering of yield by a kinetic effect since a longer reaction time raises the yield to 70%. When, however, the Cu complexes (6) and (7) were used, no ylide was formed and unchanged diazo-compound was recovered. Of other Cu compounds investigated, copper(I1) acetate and dichlorodipyridinecopper(I1) gave good yields of ylide 3 (83,54%) whereas in the cases of copper(I1) tartrate and the crown ether complex (a), unchanged diazo-compound 1 was recovered.
3355
Ph Ph f’J2
Ph o= Ph 3
J. NICHOLAS
3356
C. HOODet al.
only the arsonium and not the pyridinium ylide was formed.
2
5
nl
Me/
Me
6 7
Cl-+,- 0--CH,I
8
The lower temperature required to bring about reaction when a catalyst is present is consistent with the suggestions6 that in these circumstances reaction involves a copper complex of the diazo-compound. The observation that the diazo-compound is recovered unchanged in those cases where ylide is is not produced suggests that diazo-compound, catalyst and triphenylarsine may all be involved in a complex in those reactions leading to ylide formation. Tetra co-ordinate derivatives of Cu are accepted normally to have square planar configurations. If diazo-compound and arsine also both complex with the Cu in the reaction, the resultant intermediate complex will be octahedral. Successful ylide formation may then involve the diazo-compound and arsine occupying adjacent sites, thus enabling interaction between them. In the cases of the Cu complexes (6-8) the ligands would occupy coplanar sites around the Cu atom forcing the added diazo-compound and arsine to complex at opposite sides of the Cu atom and thus to be kept apart. In these cases formation of an ylide does not take place. The possible use of Co, Ni, Pt, Zn and vanadyl acetylacetone complexes as catalysts was also investigated, but in no case was ylide formed. Ag powder, tried because of the successful use of Cu-bronze powder as catalyst, also proved to be ineffective. Pyridinium and methylphenylsulphonium triphenylcyclopentadienylides were prepared similarly in yields of 60% and 54% respectively from 1 by reaction with pyridine or thioanisole in benzene in the presence of bis(acetylacetonato) copper( but ylides could not be obtained from diphenylsulphide or diphenylselenide. It is interesting to note that when dichlorodipyridinecopper was used as a catalyst for the preparation of the ylide 2,
Conversion of iodonium ylides into arsonium ylides The conversion of the iodonium cyclopentadienylide (9) into its triphenylarsonium analogue by melting it with triphenylarsine in the presence of either bis(acetylacetonato)copper(II) or a Cu(1) salt has been reported.“ In the absence of catalyst a higher temperature was required to achieve reaction? In the present work iodonium ylides (1613) were used as substrates. When heated with triphenylarsine in a melt or in solution in ethanol in the absence of a catalyst these iodonium ylides are not converted into arsonium ylides, but such a conversion does result in good yield if they are heated together in ethanol containing bis(acetylacetonato)copper(II). As with diazo-compounds there are indications that a certain minimum temperature may be required, but this seems to vary for different iodonium ylides. Thus ylide 10 did not react satisfactorily in dichloromethane, only a very small yield of impure arsonium ylide being obtained, whereas ylide 13 reacted equally well in dichloromethane as in ethanol. In all cases a certain minimum quantity of catalyst is required for reaction to take place but the amount differs markedly from one iodonium ylide to another. Of the ylides investigated the concentration of catalyst required per mol of ylide was: 10, 150mmol; 11 30 mmol; 12 8 mmol; 13, 5 mmol. A wide variety of different Cu derivatives was tried as catalysts and the results are listed in Table 1. For ylides 11 and 12, i.e. those of intermediate reactivity as indicated by the minimum amount of catalyst required, the results resemble those obtained with the diazo-compounds. Most of the catalysts promote reaction in good yield but Cu complexes in which it is difficult for the substrates to be adjacent to each other at the Cu atom in an octahedral complex again foil reaction. Ylide 10 appears, from the much larger amount of catalyst required, to be less reactive, and in this case a number of catalysts, which are successful for the other ylides, fail to promote reaction. A possible explanation rests on the solubilities of the catalysts in ethanol. Thus the dibenzoylmethane complex is not very soluble and it is likely that in this case the amount of catalyst in solution is insufficient to reach what appears to be the minimum required concentration for reaction. By contrast the apparently most reactive iodonium ylide 13 provides moderate yields of arsonium ylide even with those catalysts which are ineffective for the other iodonium ylides and the diazocyclopentadienes. COOEt NC
““,x,“”
PhCe
,COMe
IPh NC o= COOEt
!Ph
0
0 J+ IPtl
9 PhC
II
IO Q _’
COPh
ii ‘Ibh
IPh
12
13
The effectsof differentcopper
3357
Table 1. Conversionof iodonium ylides into arsonium ylides Iodonium ylide
(LO)
(11)
(12)
(13)
Reaction time Catalyst concentration per mol ylide (mmol) Copper derivative (@and or salt) Acetylacetone Benzoylacetone Dibenzoylmethane Dipivaloylmethane 4 5 :
2h 150
2h 30
1.5h 8
1.5h 5
Percentage yields of arsonium ylide
Dicyclohexyl-18-crown 6 Dichloropyridine Acetate Chloride Tartrate Copper bronze Tris(acetylacetonato)rhodium
81 82 0 75 82 80 00
81 85 81 82 81 82 64 0
81 81 81 83 81 83 69 0
69 14 63 14 71 14 54 51
: 31 0 0 50 0
8: 82 12 0 0 0
7: 73 82 0 0 0
52 50 63 45 41 52 43
Likewise this ylide (13) alone may be converted into an arsonium ylide by a catalyst other than Cu, tris(acetylacetonato)rhodium(III) providing a moderate yield. No conversion of iodonium ylide into arsonium ylide occurred when any of the ylides (10-13) were heated in the presence of Ni, Pt, Pd, Zn, uranyl or vanadyl complexes of acetylacetone. The differences in yields obtained from the different iodonium ylides may well be related to their differing abilities to complex with the Cu atom. The effectiveness of Cu may be associated with its softness and low redox potential.
COOMe (MeOOC),
C=-C (COOMe),
COOMe
Reactions of iodonium ylides with other substrates Each of the ylides (U-13) reacted with thioanisole in the presence of bis(acetylacetonato)copper(II) to give the corresponding methylphenylsulphonium ylides. The reactive ylide (13) also provided sulphonium ylides with diphenylsulphide and dimethylsulphoxide and a phosphonium ylide with triphenylphosphine. From attempted reactions with triphenylstibine or thiourea no stibonium or thiouronium ylides could be isolated. Possibly these reagents and not good enough carbenoid acceptors, or alternatively such ylides are formed transitorily but decompose again under the reaction conditions. The rather unreactive ylide 10 gave no sulphonium or phosphonium ylide when heated with dimethylsulphoxide or triphenylphosphine in the presence of bis(acetylacetonato)copper(II). When an ethanolic solution of ylide 13 and cyclohexene was heated in the presence of bis(acetylacetonato)copper(II) products 14 and 15 were formed,
indicative of the intermediate formation of carbene or carbenoid species. EXPERIMENTAL Diazocyclopentadienes’ and iodonium ylidessb,*were prepared as previously described. Catalysed reactions of 2,3,4-triphenyl-and 2,3,4,5-tetraphenyldiazocyclopentadienes. The diazocyclopentadiene (2 mmol) and triphenylarsine (or other carbene acceptor) (6mmol) were dissolved in dry EtOH (30 ml). Catalyst (0.15g) was added and the mixture was heated under reflux under N2 for 2 h. The hot soln was filtered and solvent was evaporated. Ether or light petroleum (b.p. M) was added to the residue. Precipitated ylide was filtered off and washed with ether. Catalysed reactions of iodonium ylides. A soln of the iodonium ylide (1 mmol) and triphenylarsine (or other carbene acceptor) (2 mmol) in EtOH (25 ml) was heated under reflux under Nr for 2 h with the catalysts listed in Table 1. The cooled soln was filtered and solvent was evaporated. Trituration with ether gave the arsonium (or other) ylide. Ylides were usually identified by comparison with authentic samples. Other ylides obtained were methylvhenylsulphonium2,2-dimethyl- 4.6 - dioxo - 1.3 - dioxan - 5 : ylide,. m.p. 133-135”[from benzene-light petroleum (b.p. 60-8W)]6 (CDCIs)1.7 s (6H), 3.4 s (3H), 7.2-7.95 m (5H) (Found: C, 58.9; H, 5.2. Cr3Hr404S requires: C, 58.9; H, 5.3%); triphenylarsoniumbis(methoxycarbonyl)methylide,m.p. 186-188” [from benzene-lkht wtroleum (b.~. 60-80°)1. 8 (CDCl3 3.35 s (6H), 7.25-7.85 m (IjH) (Found: C, 63.1; ‘H, 4.9. C23HZ,A~04 requires: C, 63.3; H, 4.8%). Reaction of phenyliodonium bis(methoxycarbonyl)methylide with cyclohexene. A mixture of 13 (6.6 g, 20mmol), bis(acetylacetonato)copper(II) (0.03 g, 0.11mmol) and cyclohexene (20 ml) was heated under reflux under N2 for 3 h. When the soln was cooled a ppt of 15 (1.07 g, 41%) formed and was filtered off, and had m.o. 123-125”(from benzene), S (CDCI,) 3.9 (Found: C, 46.4: H, 4.9: Calc. for‘CIOHtzOs: Cl 46.2; H,-‘4.7%). Solvent was evaporated from the filtrate and the residue was applied to a silica column, prepared from light petroleum (b.p. 60-80”). This solvent eluted jodbbenzene (0.38g,‘93%) and benzene eluted 14 (1.65 a. 38%). m.n. 91-93” [from Ii& netroleum (b.o. 60-8OV. 6 (CD&) 0.9-i.5 m (4H), 211-2.5 m @I), 3.7 s (3H), 3.8 s &I, (Found: C, 62.3; H, 7.6. Calc. for CllHu,04: C, 62.3; H, 7.6%). Acknowledgements-We thank Mrs. M. Smith and Mrs. S. Smith for recording, respectively, NMR spectra and analyses, and the.
J. NICHOLASC. HOODet al.
3358
University of St. Andrews for a Research Studentship (to W.A.M.). REFERENCES
‘D. Lloyd and M. I. C. Singer, Chem. Znd.510 (1967). ‘I. Gosney and D. Lloyd, Tetrahedron 29. 1697(1973). ‘B. H. Freeman and D: Lloyd, Ibid 30, 2i57 (19j4). 4K. Friedrich, W. Amann and H. Fritz, Chem. Ber. 112, 1267 (1979). saB. Y. Karele and 0. Y. Nieland, J. Org. Chem. U.S.S.R. 2, 491,
1656(1%6); 4, 132 (1%8); “r. Hayasi, T. Okada and M. Kawinisi, Bull. Chem. Sac. Japan 43, 2506(1970). %ee G. W. Cowell and A. Ledwith, Quart. Reu. Chem. Sot. 24, 119(1970). ‘B. H. Freeman, J. M. F, Gagan and D. Lloyd, Tetrahedron 29, 4307 (1973);D. Lloyd and F. I. Wasson, 1. Chem. Sot. (C) 408 (1966). *E. Gudrinietse, 0. Y. Nieland and G. Vanags, J. Gen. Chem. U.S.S.R. 27, 2777 (1957); 0. Y. Nieland and B. Y. Karele, J. Org. Chem. U.S.S.R. 7, 1674(1971).
kW~-4O20/82/223355-04$03.~/0 @I 1982 Perganos Press Ltd.
THE EFFECTS OF DIFFERENT COPPER (AND SOME OTHER) CATALYSTS ON THE CONVERSION OF TRIPHENYLAND TETRAPHENYL-DIAZOCYCLOPENTADIENES AND OF SOME PHENYLIODONIUM cd-DICARBONYLYLIDES INTO ARSONIUM AND OTHER YLIDES J. NICHOLASC. HOOD, DOUGLASLLOYD,* WILLIAM A. MACDONALD and T. MAURICESHEPHERD Departmentof Chemistry, Purdie Building,The University of St. Andrews, St. Andrews, Fife KY16 9ST, Scotland (Received in the U.K. 8 February 1982)
Abstract-Diaio-compounds or iodonium ylides may be converted into arsonium and other ylides when heated in solution with triphenylarsineor other suitable carbene (or carbenoid) acceptor, and with a suitable Cu derivative present. The effects of using diierent copper complexes and salts are described and discussed. Other metal derivativeswere for the most part ineffective as catalysts.
Two established methods for the formation of arsonium ylides are by heating either “stable” diazo-compounds’-3 or iodonium ylides4 in the presence of an arsine, commonly triphenylarsine. Ylides other than arsonium have been made similarly. Reaction is assumed to involve dissociation of the diazo-compound or iodonium ylide to provide a carbene which is at once trapped by the arsine present. In both cases reaction is frequently improved by the presence of Cu-bronze or Cu compounds and some such reactions have been shown to take place only in the presence of a Cu-catalyst?-’ It has been suggested that Cu-catalysed decomposition of both diazo-compounds6 and iodonium ylide$ may involve initial formation of a complex with the Cu derivative. Little attention has been paid to the effects on ylide formation of varying the Cu-catalyst and the present account records some findiis in this direction. Conversion of diazo-compounds ylides
into arsonium and other
Triphenylarsonium ylides can be prepared by heating mixtures of triphenylarsine and so-called “stable” diazocompounds, in which the diazo group is attached to a cyclopentadiene ring or to a C atom which also bears electron-withdrawing groups. Nearly always the yield of ylide obtained is improved by the presence of a Cucatalyst and in some cases no ylide is obtained in the absence of such a catalyst.“’ Furthermore the use of a catalyst enables the reaction to be carried out at a markedly lower temperature and in solution.’ For example reaction of diazo-2,3,4-triphenylcyclopentadiene (1) with triphenylarsine in the presence of Cu-bronze gave similar yields (-55%) of the ylide (2) whether the reaction was carried out in refluxing benzene, cyclohexane or ethanol.’ In the absence of solvent and catalyst a temperature of 150” was required for reaction to ensue and the yield was only -M?. In solution, as without solvent, a certain minimum temperature seems to be required to bring about reaction. For instance diazo-compound (1) was not converted into ylide (2) in the presence of Cu-bronze in methanol or petrol (b.p. 40-60’) as solvents. Bis(acetylacetonato)copper(II) has had wide use as a Cu-catalyst soluble in organic solvents, and with (1) and
Ph
Ph Ph
Ph
Ph&
N2
AsPh,
w
cat. heat
Ph
Ph
2
1
triphenylarsine in boiling benzene provided an 85% yield of ylide (2). Use of the Cu(II) complexes of other simple p-diketones, e.g. 3-methylacetylacetone, benzoylacetone or dibenzoylmethane, provided similar yields (90, %, 85%), but with the more sterically hindered complex of dipivaloylmethane a somewhat lower yield (67%) was obtained. Steric factors may be hindering the reaction in this case since from the more crowded diazotetraphenylcyclopentadiene (3) under the same conditions, use of the acetylacetone or dipivaloylmethane derivatives of Cu provided, respectively, yields of only 45% and 30%. Replacement of one of the 0 atoms of a /3-diketone by a N atom as in (4), also provided an efficient catalyst, producing a high yield (!W%) of ylide (2), but the bisazaderivative (5) gave a much lower yield under standard conditions (2h; 30%). It may be inferred that steric factors are causing this lowering of yield by a kinetic effect since a longer reaction time raises the yield to 70%. When, however, the Cu complexes (6) and (7) were used, no ylide was formed and unchanged diazo-compound was recovered. Of other Cu compounds investigated, copper(I1) acetate and dichlorodipyridinecopper(I1) gave good yields of ylide 3 (83,54%) whereas in the cases of copper(I1) tartrate and the crown ether complex (a), unchanged diazo-compound 1 was recovered.
3355
Ph Ph f’J2
Ph o= Ph 3
J. NICHOLAS
3356
C. HOODet al.
only the arsonium and not the pyridinium ylide was formed.
2
5
nl
Me/
Me
6 7
Cl-+,- 0--CH,I
8
The lower temperature required to bring about reaction when a catalyst is present is consistent with the suggestions6 that in these circumstances reaction involves a copper complex of the diazo-compound. The observation that the diazo-compound is recovered unchanged in those cases where ylide is is not produced suggests that diazo-compound, catalyst and triphenylarsine may all be involved in a complex in those reactions leading to ylide formation. Tetra co-ordinate derivatives of Cu are accepted normally to have square planar configurations. If diazo-compound and arsine also both complex with the Cu in the reaction, the resultant intermediate complex will be octahedral. Successful ylide formation may then involve the diazo-compound and arsine occupying adjacent sites, thus enabling interaction between them. In the cases of the Cu complexes (6-8) the ligands would occupy coplanar sites around the Cu atom forcing the added diazo-compound and arsine to complex at opposite sides of the Cu atom and thus to be kept apart. In these cases formation of an ylide does not take place. The possible use of Co, Ni, Pt, Zn and vanadyl acetylacetone complexes as catalysts was also investigated, but in no case was ylide formed. Ag powder, tried because of the successful use of Cu-bronze powder as catalyst, also proved to be ineffective. Pyridinium and methylphenylsulphonium triphenylcyclopentadienylides were prepared similarly in yields of 60% and 54% respectively from 1 by reaction with pyridine or thioanisole in benzene in the presence of bis(acetylacetonato) copper( but ylides could not be obtained from diphenylsulphide or diphenylselenide. It is interesting to note that when dichlorodipyridinecopper was used as a catalyst for the preparation of the ylide 2,
Conversion of iodonium ylides into arsonium ylides The conversion of the iodonium cyclopentadienylide (9) into its triphenylarsonium analogue by melting it with triphenylarsine in the presence of either bis(acetylacetonato)copper(II) or a Cu(1) salt has been reported.“ In the absence of catalyst a higher temperature was required to achieve reaction? In the present work iodonium ylides (1613) were used as substrates. When heated with triphenylarsine in a melt or in solution in ethanol in the absence of a catalyst these iodonium ylides are not converted into arsonium ylides, but such a conversion does result in good yield if they are heated together in ethanol containing bis(acetylacetonato)copper(II). As with diazo-compounds there are indications that a certain minimum temperature may be required, but this seems to vary for different iodonium ylides. Thus ylide 10 did not react satisfactorily in dichloromethane, only a very small yield of impure arsonium ylide being obtained, whereas ylide 13 reacted equally well in dichloromethane as in ethanol. In all cases a certain minimum quantity of catalyst is required for reaction to take place but the amount differs markedly from one iodonium ylide to another. Of the ylides investigated the concentration of catalyst required per mol of ylide was: 10, 150mmol; 11 30 mmol; 12 8 mmol; 13, 5 mmol. A wide variety of different Cu derivatives was tried as catalysts and the results are listed in Table 1. For ylides 11 and 12, i.e. those of intermediate reactivity as indicated by the minimum amount of catalyst required, the results resemble those obtained with the diazo-compounds. Most of the catalysts promote reaction in good yield but Cu complexes in which it is difficult for the substrates to be adjacent to each other at the Cu atom in an octahedral complex again foil reaction. Ylide 10 appears, from the much larger amount of catalyst required, to be less reactive, and in this case a number of catalysts, which are successful for the other ylides, fail to promote reaction. A possible explanation rests on the solubilities of the catalysts in ethanol. Thus the dibenzoylmethane complex is not very soluble and it is likely that in this case the amount of catalyst in solution is insufficient to reach what appears to be the minimum required concentration for reaction. By contrast the apparently most reactive iodonium ylide 13 provides moderate yields of arsonium ylide even with those catalysts which are ineffective for the other iodonium ylides and the diazocyclopentadienes. COOEt NC
““,x,“”
PhCe
,COMe
IPh NC o= COOEt
!Ph
0
0 J+ IPtl
9 PhC
II
IO Q _’
COPh
ii ‘Ibh
IPh
12
13
The effectsof differentcopper
3357
Table 1. Conversionof iodonium ylides into arsonium ylides Iodonium ylide
(LO)
(11)
(12)
(13)
Reaction time Catalyst concentration per mol ylide (mmol) Copper derivative (@and or salt) Acetylacetone Benzoylacetone Dibenzoylmethane Dipivaloylmethane 4 5 :
2h 150
2h 30
1.5h 8
1.5h 5
Percentage yields of arsonium ylide
Dicyclohexyl-18-crown 6 Dichloropyridine Acetate Chloride Tartrate Copper bronze Tris(acetylacetonato)rhodium
81 82 0 75 82 80 00
81 85 81 82 81 82 64 0
81 81 81 83 81 83 69 0
69 14 63 14 71 14 54 51
: 31 0 0 50 0
8: 82 12 0 0 0
7: 73 82 0 0 0
52 50 63 45 41 52 43
Likewise this ylide (13) alone may be converted into an arsonium ylide by a catalyst other than Cu, tris(acetylacetonato)rhodium(III) providing a moderate yield. No conversion of iodonium ylide into arsonium ylide occurred when any of the ylides (10-13) were heated in the presence of Ni, Pt, Pd, Zn, uranyl or vanadyl complexes of acetylacetone. The differences in yields obtained from the different iodonium ylides may well be related to their differing abilities to complex with the Cu atom. The effectiveness of Cu may be associated with its softness and low redox potential.
COOMe (MeOOC),
C=-C (COOMe),
COOMe
Reactions of iodonium ylides with other substrates Each of the ylides (U-13) reacted with thioanisole in the presence of bis(acetylacetonato)copper(II) to give the corresponding methylphenylsulphonium ylides. The reactive ylide (13) also provided sulphonium ylides with diphenylsulphide and dimethylsulphoxide and a phosphonium ylide with triphenylphosphine. From attempted reactions with triphenylstibine or thiourea no stibonium or thiouronium ylides could be isolated. Possibly these reagents and not good enough carbenoid acceptors, or alternatively such ylides are formed transitorily but decompose again under the reaction conditions. The rather unreactive ylide 10 gave no sulphonium or phosphonium ylide when heated with dimethylsulphoxide or triphenylphosphine in the presence of bis(acetylacetonato)copper(II). When an ethanolic solution of ylide 13 and cyclohexene was heated in the presence of bis(acetylacetonato)copper(II) products 14 and 15 were formed,
indicative of the intermediate formation of carbene or carbenoid species. EXPERIMENTAL Diazocyclopentadienes’ and iodonium ylidessb,*were prepared as previously described. Catalysed reactions of 2,3,4-triphenyl-and 2,3,4,5-tetraphenyldiazocyclopentadienes. The diazocyclopentadiene (2 mmol) and triphenylarsine (or other carbene acceptor) (6mmol) were dissolved in dry EtOH (30 ml). Catalyst (0.15g) was added and the mixture was heated under reflux under N2 for 2 h. The hot soln was filtered and solvent was evaporated. Ether or light petroleum (b.p. M) was added to the residue. Precipitated ylide was filtered off and washed with ether. Catalysed reactions of iodonium ylides. A soln of the iodonium ylide (1 mmol) and triphenylarsine (or other carbene acceptor) (2 mmol) in EtOH (25 ml) was heated under reflux under Nr for 2 h with the catalysts listed in Table 1. The cooled soln was filtered and solvent was evaporated. Trituration with ether gave the arsonium (or other) ylide. Ylides were usually identified by comparison with authentic samples. Other ylides obtained were methylvhenylsulphonium2,2-dimethyl- 4.6 - dioxo - 1.3 - dioxan - 5 : ylide,. m.p. 133-135”[from benzene-light petroleum (b.p. 60-8W)]6 (CDCIs)1.7 s (6H), 3.4 s (3H), 7.2-7.95 m (5H) (Found: C, 58.9; H, 5.2. Cr3Hr404S requires: C, 58.9; H, 5.3%); triphenylarsoniumbis(methoxycarbonyl)methylide,m.p. 186-188” [from benzene-lkht wtroleum (b.~. 60-80°)1. 8 (CDCl3 3.35 s (6H), 7.25-7.85 m (IjH) (Found: C, 63.1; ‘H, 4.9. C23HZ,A~04 requires: C, 63.3; H, 4.8%). Reaction of phenyliodonium bis(methoxycarbonyl)methylide with cyclohexene. A mixture of 13 (6.6 g, 20mmol), bis(acetylacetonato)copper(II) (0.03 g, 0.11mmol) and cyclohexene (20 ml) was heated under reflux under N2 for 3 h. When the soln was cooled a ppt of 15 (1.07 g, 41%) formed and was filtered off, and had m.o. 123-125”(from benzene), S (CDCI,) 3.9 (Found: C, 46.4: H, 4.9: Calc. for‘CIOHtzOs: Cl 46.2; H,-‘4.7%). Solvent was evaporated from the filtrate and the residue was applied to a silica column, prepared from light petroleum (b.p. 60-80”). This solvent eluted jodbbenzene (0.38g,‘93%) and benzene eluted 14 (1.65 a. 38%). m.n. 91-93” [from Ii& netroleum (b.o. 60-8OV. 6 (CD&) 0.9-i.5 m (4H), 211-2.5 m @I), 3.7 s (3H), 3.8 s &I, (Found: C, 62.3; H, 7.6. Calc. for CllHu,04: C, 62.3; H, 7.6%). Acknowledgements-We thank Mrs. M. Smith and Mrs. S. Smith for recording, respectively, NMR spectra and analyses, and the.
J. NICHOLASC. HOODet al.
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University of St. Andrews for a Research Studentship (to W.A.M.). REFERENCES
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