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A selenurane derivative promotes β-fragmentation of carbinolamides leading to cyclic imides
Temkdron Lcuas. Vol. 35. No. 7. pp. 1083-1086.1994 ElscvicrSciare L&t RiIlKdinGlUtBliti -9W S6.OOtO.tM
004@4039(93)EO379-x
A Selenurane Derivative Promotes P-Fragmentation of Carbinolamides
Leading to Cyclic Imides
Rosa L. Dora, Cosme G. Francisco, Rrncsto Stt&ez* Instituto&?Roductos Natumlm y Agmbiologfa &I C.S.I.C., CxumuadeLaEspaanza2,38#16_LaLaguna,T~c,Spain.
Abstract: The a&y rcuiical intermediates generated by reaction of carbinokmides with diphmylselenium hydroxyacetate (1) in the presence of iodine and under imzdia~ioa with visible light Argo ~fiagmmation to t@rd 3d-substitntd cyclic imides in good yields.
Although tetravalent organoselenium compounds have been known for many years.’ their chemical pqerties have been little investigated2 In a previous communication we have introduced the diphenylseleniurn hydroxyacetate (I)-iodine system as an efficient reagent to generate alkoxy radical~.~ Alkoxy free radicals are able to undergo a wide variety of synthetically pscission
processesP
carbinolamides6c
useful intramolecular
hydrogen abstraction4 and
For some years, we have been studying the photolysis of hemiacetals,eu
in the presence of a hypervalent
iodine reagent and iodine, developing
lacu@
and
novel methodolo-
gies which successfully allow the synthesis of lactones, anhydrides and cyclic imides, respectively. These last products are very significant not only as reagents,’ but also as useful in-s for the synthesis of pyrroliidine
alkaloids,8 and the biosynthesis
Herein, we describe our observations
of vitamin BI~.~ on the course of alkoxy radical generation by using the selenium
(IV) reagent-iodine system. As expected, this method promotes regioselective
@fragmentation of carbino-
lamides leading to 3,4-substituted cyclic imides cleanly without any by-products (Scheme I, R = H, alkyl).
Scheme I The procedure was applied to several carbinolamides 4-one (2),”
bicyclo[3.3.0]
derivatives
(6),‘l (S),12 (lO)k
such as 2-hydmxy-3-azatricyclo[5.2.1.02~decanand the stem&l
substrates were obtained fTom the cqresponding a&unsaturated sium cyanide aud hydrolysis of the nitrile intcrmediate~.‘~
carbinolamide
(13).r3 All these
carbcmyl compounds by addition of potas-
A typical ptocedum is as follows: a mixture of carbinolamide (2) (0.30 mmol) in carbon tetrachloride (10 ml) containing diphenylselenium hydroxyacetate (0.45 mmol) and iodine (0.33 mmol) was irradiated with two 100 W tungsten-filament lamps for 40 min at 80 ‘C. The reaction mixture was then poured into 1083
ii: 3 0
0
I I 8
7
z
9
I 10
18
14
aqueous sodium thiosulfate solution and extracted with methylene cbltide.
crude with EtOAc-n-hexane
mixnues
Rotative chromatography of the
of increasing polarity gave the isomeric Moimides
(3,‘& 4,‘4b see
Table entry 1) in 78% yield,15 which by reduction with tributyltin hydride gave a sole product (5)16 in 86%
yield. When the reaction was performed at temperatures lower than 80 ‘C the conversion was not complete as occurred with the 4,4-disubstituted hicycloderivatives (6) (entry 2) and (8) (entry 3). recovering starting material in both cases. However, conversion of the 4,4disubstituted bicycloderivative (8) maintaining the temperature at 80 ‘C was complete in 1 hour (entry 4). In the case of the 4-monosubstituted cattkolamide (10) ring expansion occuned givingrisetoan 8-membered imide (ll)& together with the S-mem~~imide (12)& (entry 5). Finally. fragmentation of the steroidal carbinolamide (13) gave a sole product (14jk in excellent yield (94%) (entry 6).
Table. jM?agmentation of C!arbinolamidesa by Diphenylselenium Hydroxyacetate (1). substrate
Entry
Conditialsc
Reagentsb
PlOdUCtS
Time (h)
Temp. CC)
(Yield %)
1
2
M/1.1
0.6
80
3 (3% 4 (39)
2
6
1.5/l .o
6.5
40
7 C16)d
3
8
M/1.1
1
60
9 C12)d
4
8
lS/l.l
1
80
9 (74)
5
10
1.5/1.1
1.2
80
11 (74), 12 (22)
13
1.5/1.0
1
80
14 (94)
~mmol)
6
,
a) compounas (2). (6). (8) and (10) arc m;
b) Mmoles of diplwmylacknim hydmxyacaetclmmdes ofiodinepammolof subseate;c)AuthereacriaLswerepafonaaSin~tetrachloridt.3omlpermmolofsubstrate;d)calculatedontransformed product (70%).
A plausible mechanism is shown in scheme II; the carbinolamide radical may undergo a fast but reversible kfkagmentation of the Ct-Cs bond to give the ldnetic radical (A), and a slower but essentially irreversible Cl-C8 cleavage to afford the thenaodynamic primary radical (B). The second step rate would be dependent on the efficiency of radical trapping (among or&r factors). In the hind&
carbinolamides (6,s
and 13) (Rt = R2 = alkyl) k2 must be greater than kt and succinimide derivatives are formed exclusively. However, in the less hindered carbinolamide (10) (Rt = I-I,R2 = alkyl) k2 must be smaller or similar than kl directing the equilibrium mainly to the formation of the unexpected eight-membered imide (11).” We were unable to detect the co-formation of any by-products resulting from the Cl-NH fission to give the corregement into isoc~anates.‘~ sponding amide-radical that eventually can be transformed by amidyl m
0
0
(W Scheme II In view of these results we can conclude that diphenylselenium hydroxyacetate is an interesting alternative to other oxidizing agents, proving tu be efficient, mild and selective. AcknowkdgementaThis work wassupported by the Iavestigatlon Rogramme ne PB90-0083 of the Dire&& General de Invest&a&n Cient@ica y Tknica We thank to the D&c&n General de Universidades e Investigaci6n de1 Gobiemo de canarias for a fellowship to R.L. Dorta.
1086
REFERENCES AND NOTES 1. a) Fmta, D.G.. Red. Trav. Chim. Pays-Bas. 1935.54.447; 2.
a) Marina. J.P.; Larsen, RD.
b) Horn.. V.; paetzold, R Anwg. A&. Ckm.,
1973,398.~86.
J. Am Ckm. Sot.. 1981,103,4642. b) Marina, J.P.; DIU. S. Temhe&on Let:., 1987,28.4007.
3.
Dorta, R-L.; Francisco. C.G.; Freirc. R; Su&ez., ELTerruk&on
4.
For reviews see: a) Heusler. K.: Kalvoda, J. in Organic
Len.. 1986,29.5429.
Reaction in Steroid Ckmi.a~
eds., Fried. J.: Edwards. J.A., VIM
Nostmn Reinhold. New York, 1971, vol. 2, p_ 237: b) Kalvoda, J.; Heusla, K. Synthsis, 1971, sol. 5. O’Dell. DE.; Lopa, J.T.; Macdonald. T.L. J. Org. Ckm. 1988,53, 5225 and tiezences cited the&q Kobayasbi, K.; Sasaki, A., Kane, Y.; Suginome,H. Tetrahedron. 1991.47, 7245; Kobayashi, K.; Uoh. M_; Sasaki, A.; Suginome, H. ibid., 1991.47.5437; ELlwood,C.; F’attencb, G.; Terrukdron Len., 1991,32, 1591. 6. a) Freire. R; Marrao. J.J.; Rodrlgucz. MS.: Suk.z, E. Tefrak&on Lea.. 1986.27. 383; de Atmas. P.; Francisco, G.C.; Sti, E. Angc~. Ckm., Int. Ed. &#I. 1992,3X, 772: de Armas. P.; Francisco, G.C.: Su&rez, E. J. Am. Ckm. Sot.. 1993. IIS. 8865; b) l-knkkz. R.; Marero, JJ.; Suka, E.; Perales, A. Tewak&on Len.. l!W, 29, 5979; c) Hem&&z, R.; Marreo. J.J.; Meli&
D.: S&ez,
E Tewakdrot~
liea.
1988.29.6661.
7. Nicolaou, K.C.; Petasis. N.A. Seletiwn in Namral Products Sywksis, 8.
Thai. Y-M.;
CIS, Phih&lphia,
1934, p. 68.
Ke, B-W.; Yang, C-T.; Li, C-H.; Tarakdron Mt., 1992, 33, 7895; Niva, H.; Miyachi, Y.; Okamoto, 0.;
Uosalri. Y.; Yamtxla, K. Tsaahedron Left., 1986. 27, 46015;:Kametm& T; Yukawa, H.: Honda, T. 1. Ckm Commun., 1986. 651: Hiemstm. Stto, M.H.A.H.: Vijn, RJ.: Speckmam, N.. J. Org. Ckm.. Ebhobn, EJ. Teauk&onL.err.,
l985.26,3311;
9. Battersby, A-R.; Westwood. W.S. J. Ckm.
Flitach. W.; Wempmaan. P. ibid., 1981.22.719. Sot., Perkin I, 1987, 1679; Block, M.It; Zimmerman,
Turner, S.P.D.; Westwood, S.W.; Leepcr, FL; Bat-by, Block, M.H.; Sheq, 10.
AR. J. Ckm.
Z-C.; zimmennsn, S.C.; Battersby, AR
Compound (2): m.p. 206-207 “C (l&OH);
Ckm.
Sot.,
1985. SO. 4014; Keck, GE
Sot., Ckm.
Comma,
S.C.: Hendeason, G.B.;
1985, 1061; T&cr.
S.P.D.;
ibid., 1985,583.
lR (KBr) vmu 3354, 3176, 1713, 1650 cm‘]; ‘HNMR (200 MHZ. CDaD)
8~
2.72 OH. d. J 18 Hz), 2.48 (1H. d, J 18 Hz). 2.20 (1H. bs, wt~ 8 Hz), 2.00-1.82 (3H, m), 1.65-1.25 (6H. m); 13CNMR(SO.3 MHZ, CD30D) & 180.23 (s), 9763 (s), 50.34 (d), 47.24 (d), 44.78 (d), 37.49 (t), 35.46 (I), 29.20 (t), 23.51 (t); MS m/z 167.09408 (M+. 11%). 11. Stevens, R-V.; Christensen, C.G.: Eklmonson, WL.; Kaplan, M.; Reid, E.B.; Wentland, M.P. J. Am. Ckm.
Sot..
1971, 93,
6629. 12. Hemhdez. R.; MeliAn,D.: Sdrez, E. anpublished rest&a. 13. Naga@ W.; Hirai, S.; Itazaki. H.; Takeda, K. J. Org. Ckm., 1961.26, 2413. 14. Compounds 3 aad 4 were padaily resdved by cluomatogqby.
The t-&&e
stawchemistries were established by detent&
nation of the coupling constants of the iodine geminal proton by the PCMODEL ptogcam (Stxna Software) and simulation of the signal by tbe RACGGM
laogram (P.F. Scbatz, University of Wisconsin); a) a-Isomer (3) IR (CHC13) vmu 3403,
1785. 1725 cm-l; ‘HNMR (200 MHz. CDCl3) 8~ 8.35 (1H. bs. NH), 4.46 (Hi, m, wt~ 16 Hz), 2.95-2.80 (3H, m), 2.51-1.33 (8H, m); MS m/z 294 (M++ 1, 3%). 166 (100%); b) f3-lsomex (4) IR (CHcl3) vmu 3403, 1785, 1725 cm-‘; ‘HNMR (200 Ml-k CDCly) 8.30 (lH, bs. NH), 4.22 (lH, dddd. J 6, 12, 12. 6 Hz). 3.05-2.82 (3H, m). 262-1.29 (8H, m); MS m/z 294 &l++ 1.3%),
166.6.08679&I+-I, 100%).
15. Dipbenyl selenide was also isolated in all cases. It was cbamc&zd 16. Compound (5): m.p. 123.7-124.1 “C (EtGAJn-bexane);
by comparison with an autbuuic sample.
lR (CHQ)
v-
3405, 1782, 1724 cm-t; ‘HNMR
CDC13) 8~ 8.45 (1H. bs. NH), 2.97-2.74 (W, m), 2.52-2.27 (2Hm). 1.93-1.56 (6H. m), 1X-1.21
(200 MHz.
(ZH. m); 13CNMR (50.3
MHZ, CD3OD) 8c 183.18 (s), 180.54 (s), 46.16 (d). 42.29 (d). 34.65 (t), 31.36 (t). 29.69 (t). 26.30 (t). 25.93 (t); MS m/z 168.10271 @I++ 1.3%).
167.09513 (M+, 1%). 99.11774 (100%).
17. A similar argument has been used by: Be&with. A.L.J.; Ka&ukas. to explain the ~-fragmentation of 9dfdinoxyl
R.; Synez-Lyons, M.R. J. Org. Ckm..
rdirais.
18. Baumgarten. H.E.; Smith, H.L.; Stakalis. A. J. Org. Ckm,
197§,40,3554.
(Received in UK 27 October 1993; revised 6 December 1993; accepted 10 December 1993)
WED,48.4718
004@4039(93)EO379-x
A Selenurane Derivative Promotes P-Fragmentation of Carbinolamides
Leading to Cyclic Imides
Rosa L. Dora, Cosme G. Francisco, Rrncsto Stt&ez* Instituto&?Roductos Natumlm y Agmbiologfa &I C.S.I.C., CxumuadeLaEspaanza2,38#16_LaLaguna,T~c,Spain.
Abstract: The a&y rcuiical intermediates generated by reaction of carbinokmides with diphmylselenium hydroxyacetate (1) in the presence of iodine and under imzdia~ioa with visible light Argo ~fiagmmation to t@rd 3d-substitntd cyclic imides in good yields.
Although tetravalent organoselenium compounds have been known for many years.’ their chemical pqerties have been little investigated2 In a previous communication we have introduced the diphenylseleniurn hydroxyacetate (I)-iodine system as an efficient reagent to generate alkoxy radical~.~ Alkoxy free radicals are able to undergo a wide variety of synthetically pscission
processesP
carbinolamides6c
useful intramolecular
hydrogen abstraction4 and
For some years, we have been studying the photolysis of hemiacetals,eu
in the presence of a hypervalent
iodine reagent and iodine, developing
lacu@
and
novel methodolo-
gies which successfully allow the synthesis of lactones, anhydrides and cyclic imides, respectively. These last products are very significant not only as reagents,’ but also as useful in-s for the synthesis of pyrroliidine
alkaloids,8 and the biosynthesis
Herein, we describe our observations
of vitamin BI~.~ on the course of alkoxy radical generation by using the selenium
(IV) reagent-iodine system. As expected, this method promotes regioselective
@fragmentation of carbino-
lamides leading to 3,4-substituted cyclic imides cleanly without any by-products (Scheme I, R = H, alkyl).
Scheme I The procedure was applied to several carbinolamides 4-one (2),”
bicyclo[3.3.0]
derivatives
(6),‘l (S),12 (lO)k
such as 2-hydmxy-3-azatricyclo[5.2.1.02~decanand the stem&l
substrates were obtained fTom the cqresponding a&unsaturated sium cyanide aud hydrolysis of the nitrile intcrmediate~.‘~
carbinolamide
(13).r3 All these
carbcmyl compounds by addition of potas-
A typical ptocedum is as follows: a mixture of carbinolamide (2) (0.30 mmol) in carbon tetrachloride (10 ml) containing diphenylselenium hydroxyacetate (0.45 mmol) and iodine (0.33 mmol) was irradiated with two 100 W tungsten-filament lamps for 40 min at 80 ‘C. The reaction mixture was then poured into 1083
ii: 3 0
0
I I 8
7
z
9
I 10
18
14
aqueous sodium thiosulfate solution and extracted with methylene cbltide.
crude with EtOAc-n-hexane
mixnues
Rotative chromatography of the
of increasing polarity gave the isomeric Moimides
(3,‘& 4,‘4b see
Table entry 1) in 78% yield,15 which by reduction with tributyltin hydride gave a sole product (5)16 in 86%
yield. When the reaction was performed at temperatures lower than 80 ‘C the conversion was not complete as occurred with the 4,4-disubstituted hicycloderivatives (6) (entry 2) and (8) (entry 3). recovering starting material in both cases. However, conversion of the 4,4disubstituted bicycloderivative (8) maintaining the temperature at 80 ‘C was complete in 1 hour (entry 4). In the case of the 4-monosubstituted cattkolamide (10) ring expansion occuned givingrisetoan 8-membered imide (ll)& together with the S-mem~~imide (12)& (entry 5). Finally. fragmentation of the steroidal carbinolamide (13) gave a sole product (14jk in excellent yield (94%) (entry 6).
Table. jM?agmentation of C!arbinolamidesa by Diphenylselenium Hydroxyacetate (1). substrate
Entry
Conditialsc
Reagentsb
PlOdUCtS
Time (h)
Temp. CC)
(Yield %)
1
2
M/1.1
0.6
80
3 (3% 4 (39)
2
6
1.5/l .o
6.5
40
7 C16)d
3
8
M/1.1
1
60
9 C12)d
4
8
lS/l.l
1
80
9 (74)
5
10
1.5/1.1
1.2
80
11 (74), 12 (22)
13
1.5/1.0
1
80
14 (94)
~mmol)
6
,
a) compounas (2). (6). (8) and (10) arc m;
b) Mmoles of diplwmylacknim hydmxyacaetclmmdes ofiodinepammolof subseate;c)AuthereacriaLswerepafonaaSin~tetrachloridt.3omlpermmolofsubstrate;d)calculatedontransformed product (70%).
A plausible mechanism is shown in scheme II; the carbinolamide radical may undergo a fast but reversible kfkagmentation of the Ct-Cs bond to give the ldnetic radical (A), and a slower but essentially irreversible Cl-C8 cleavage to afford the thenaodynamic primary radical (B). The second step rate would be dependent on the efficiency of radical trapping (among or&r factors). In the hind&
carbinolamides (6,s
and 13) (Rt = R2 = alkyl) k2 must be greater than kt and succinimide derivatives are formed exclusively. However, in the less hindered carbinolamide (10) (Rt = I-I,R2 = alkyl) k2 must be smaller or similar than kl directing the equilibrium mainly to the formation of the unexpected eight-membered imide (11).” We were unable to detect the co-formation of any by-products resulting from the Cl-NH fission to give the corregement into isoc~anates.‘~ sponding amide-radical that eventually can be transformed by amidyl m
0
0
(W Scheme II In view of these results we can conclude that diphenylselenium hydroxyacetate is an interesting alternative to other oxidizing agents, proving tu be efficient, mild and selective. AcknowkdgementaThis work wassupported by the Iavestigatlon Rogramme ne PB90-0083 of the Dire&& General de Invest&a&n Cient@ica y Tknica We thank to the D&c&n General de Universidades e Investigaci6n de1 Gobiemo de canarias for a fellowship to R.L. Dorta.
1086
REFERENCES AND NOTES 1. a) Fmta, D.G.. Red. Trav. Chim. Pays-Bas. 1935.54.447; 2.
a) Marina. J.P.; Larsen, RD.
b) Horn.. V.; paetzold, R Anwg. A&. Ckm.,
1973,398.~86.
J. Am Ckm. Sot.. 1981,103,4642. b) Marina, J.P.; DIU. S. Temhe&on Let:., 1987,28.4007.
3.
Dorta, R-L.; Francisco. C.G.; Freirc. R; Su&ez., ELTerruk&on
4.
For reviews see: a) Heusler. K.: Kalvoda, J. in Organic
Len.. 1986,29.5429.
Reaction in Steroid Ckmi.a~
eds., Fried. J.: Edwards. J.A., VIM
Nostmn Reinhold. New York, 1971, vol. 2, p_ 237: b) Kalvoda, J.; Heusla, K. Synthsis, 1971, sol. 5. O’Dell. DE.; Lopa, J.T.; Macdonald. T.L. J. Org. Ckm. 1988,53, 5225 and tiezences cited the&q Kobayasbi, K.; Sasaki, A., Kane, Y.; Suginome,H. Tetrahedron. 1991.47, 7245; Kobayashi, K.; Uoh. M_; Sasaki, A.; Suginome, H. ibid., 1991.47.5437; ELlwood,C.; F’attencb, G.; Terrukdron Len., 1991,32, 1591. 6. a) Freire. R; Marrao. J.J.; Rodrlgucz. MS.: Suk.z, E. Tefrak&on Lea.. 1986.27. 383; de Atmas. P.; Francisco, G.C.; Sti, E. Angc~. Ckm., Int. Ed. &#I. 1992,3X, 772: de Armas. P.; Francisco, G.C.: Su&rez, E. J. Am. Ckm. Sot.. 1993. IIS. 8865; b) l-knkkz. R.; Marero, JJ.; Suka, E.; Perales, A. Tewak&on Len.. l!W, 29, 5979; c) Hem&&z, R.; Marreo. J.J.; Meli&
D.: S&ez,
E Tewakdrot~
liea.
1988.29.6661.
7. Nicolaou, K.C.; Petasis. N.A. Seletiwn in Namral Products Sywksis, 8.
Thai. Y-M.;
CIS, Phih&lphia,
1934, p. 68.
Ke, B-W.; Yang, C-T.; Li, C-H.; Tarakdron Mt., 1992, 33, 7895; Niva, H.; Miyachi, Y.; Okamoto, 0.;
Uosalri. Y.; Yamtxla, K. Tsaahedron Left., 1986. 27, 46015;:Kametm& T; Yukawa, H.: Honda, T. 1. Ckm Commun., 1986. 651: Hiemstm. Stto, M.H.A.H.: Vijn, RJ.: Speckmam, N.. J. Org. Ckm.. Ebhobn, EJ. Teauk&onL.err.,
l985.26,3311;
9. Battersby, A-R.; Westwood. W.S. J. Ckm.
Flitach. W.; Wempmaan. P. ibid., 1981.22.719. Sot., Perkin I, 1987, 1679; Block, M.It; Zimmerman,
Turner, S.P.D.; Westwood, S.W.; Leepcr, FL; Bat-by, Block, M.H.; Sheq, 10.
AR. J. Ckm.
Z-C.; zimmennsn, S.C.; Battersby, AR
Compound (2): m.p. 206-207 “C (l&OH);
Ckm.
Sot.,
1985. SO. 4014; Keck, GE
Sot., Ckm.
Comma,
S.C.: Hendeason, G.B.;
1985, 1061; T&cr.
S.P.D.;
ibid., 1985,583.
lR (KBr) vmu 3354, 3176, 1713, 1650 cm‘]; ‘HNMR (200 MHZ. CDaD)
8~
2.72 OH. d. J 18 Hz), 2.48 (1H. d, J 18 Hz). 2.20 (1H. bs, wt~ 8 Hz), 2.00-1.82 (3H, m), 1.65-1.25 (6H. m); 13CNMR(SO.3 MHZ, CD30D) & 180.23 (s), 9763 (s), 50.34 (d), 47.24 (d), 44.78 (d), 37.49 (t), 35.46 (I), 29.20 (t), 23.51 (t); MS m/z 167.09408 (M+. 11%). 11. Stevens, R-V.; Christensen, C.G.: Eklmonson, WL.; Kaplan, M.; Reid, E.B.; Wentland, M.P. J. Am. Ckm.
Sot..
1971, 93,
6629. 12. Hemhdez. R.; MeliAn,D.: Sdrez, E. anpublished rest&a. 13. Naga@ W.; Hirai, S.; Itazaki. H.; Takeda, K. J. Org. Ckm., 1961.26, 2413. 14. Compounds 3 aad 4 were padaily resdved by cluomatogqby.
The t-&&e
stawchemistries were established by detent&
nation of the coupling constants of the iodine geminal proton by the PCMODEL ptogcam (Stxna Software) and simulation of the signal by tbe RACGGM
laogram (P.F. Scbatz, University of Wisconsin); a) a-Isomer (3) IR (CHC13) vmu 3403,
1785. 1725 cm-l; ‘HNMR (200 MHz. CDCl3) 8~ 8.35 (1H. bs. NH), 4.46 (Hi, m, wt~ 16 Hz), 2.95-2.80 (3H, m), 2.51-1.33 (8H, m); MS m/z 294 (M++ 1, 3%). 166 (100%); b) f3-lsomex (4) IR (CHcl3) vmu 3403, 1785, 1725 cm-‘; ‘HNMR (200 Ml-k CDCly) 8.30 (lH, bs. NH), 4.22 (lH, dddd. J 6, 12, 12. 6 Hz). 3.05-2.82 (3H, m). 262-1.29 (8H, m); MS m/z 294 &l++ 1.3%),
166.6.08679&I+-I, 100%).
15. Dipbenyl selenide was also isolated in all cases. It was cbamc&zd 16. Compound (5): m.p. 123.7-124.1 “C (EtGAJn-bexane);
by comparison with an autbuuic sample.
lR (CHQ)
v-
3405, 1782, 1724 cm-t; ‘HNMR
CDC13) 8~ 8.45 (1H. bs. NH), 2.97-2.74 (W, m), 2.52-2.27 (2Hm). 1.93-1.56 (6H. m), 1X-1.21
(200 MHz.
(ZH. m); 13CNMR (50.3
MHZ, CD3OD) 8c 183.18 (s), 180.54 (s), 46.16 (d). 42.29 (d). 34.65 (t), 31.36 (t). 29.69 (t). 26.30 (t). 25.93 (t); MS m/z 168.10271 @I++ 1.3%).
167.09513 (M+, 1%). 99.11774 (100%).
17. A similar argument has been used by: Be&with. A.L.J.; Ka&ukas. to explain the ~-fragmentation of 9dfdinoxyl
R.; Synez-Lyons, M.R. J. Org. Ckm..
rdirais.
18. Baumgarten. H.E.; Smith, H.L.; Stakalis. A. J. Org. Ckm,
197§,40,3554.
(Received in UK 27 October 1993; revised 6 December 1993; accepted 10 December 1993)
WED,48.4718