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Carbon-13 NMR spectroscopy of sulfonium ylides
TetrahedronLettersVol. 21, pp 2109 - 2112 OPergamon press Ltd. 1980.Printedin Great Britain
0040-4039/60/0515-2109#02.00/0
CARBON-13 NHB SPECTROSCOPY OF SULFONIUM YLIDES G.BarbareLla, P.Dembech and A.Garbesi Laboratorio C.N.R.,via Tolara di Sotto,89-OZEANO HMXLIA (Bologna)- ITALY
C-13 NMB data for a series of stabilized and unstabilized ylides indicate flattening at the ylidic carbon with respect to the Parent salts. For unst*ilired ylides association between the oarbanionic center and the lithium cation cannot be neglected. Sulfunium yfides are the intermediates in the B/D base-catafysed exchange' and in the methylation2 of sulfonium safts,both reactions being often highly stereoselective.The results of the exchange reaction have been explained on the basis of a pyramidal ylidic carbon and this interpretation is supported by & lb initio calculations .The results of the methylation reaction may be accounted for either by a planar or by a pyramidal ylidic carbona. Direct experimental evi dence on the structure of sulfonium ylides appears to be a necessary step to e& cidate the factors determining the stereosslectivity of these reactions,in anale gy with what has been done for other sulfur compounds3. To our knowledge only a few proton4 and carbon-13' NMR data on stabilized sulfonium ylides (i.e. bearing electron-withdrawing groups attached to the ylidic carbon) have been reported. On the contrary an abundance of data exists on p~~p~ni~ yli.des,for which ex6,7 perimental and theoretical7 evidence indicates a pyramidal and a planar geomg try at phosphorus and carbon respectively. We present here the C-L3 parameters
( 8,
1
a series of stabifised (l-5) and unstabilized
Sew) of the carbanionic carbon for (6-8) sulfonium ylides,which indi-
cate that the ylidic carbon is more flattened (if not planar) than in the corresponding salts. compounds l-5 are either known compounds or were prepared accord 8 ing to established procedures .Compounds 6-8 were obtained directly in the NMR 9 tube at -70°C by treatment of the salts in THY?-d8 with LiCHC12(1.2 eq.) ,After recording the spectra the starting salts were regenerated by quenching with CH30H:decomposition was less than 20%. Spectra were recorded on a Varian FT-80 spectrometer at probe temperature are in Hz and
(25Lt2W
for l-5 and at -7Wc
for 6-8.
3's
b's are in ppsk with respect to cx32CB or TBP-d 8. The accuracy is 2f09
2112
well
as on the general
aspects
of the geometry
of sulfonium
ylides.
References 1. a)G.Barbarella,P.Dembech,A.Garbesi references
therein;
and A.Fava,J.Am.Chem.Soc
.,1975.5883
and
b)G.Barbarella,P.Dembech,A.Garbesi,F.Bernardi,A.Bottoni
and A.Fava,ibid.,1978,200. 2. a)D.M.Roush,E.M.Price,L.K.Templeton,D.H.Templeton =,2971;
b)A.Garbesi,Tetrahedron
3. a)A.J.Abatjoglou,E.L.Eliel Chassaing
and C!.H.Heathcock,ibid.,
Letters,B,547.
and L.F.Kuyper,J.Am.Chem.Soc
and A.Marguet,Tetrahedron,a,l399:
..=,8262;
R.Lett
b)G.
and G.Chassaing,ibid -*
I
-,2705. 4. K.W.Ratts,Tetrahedron
Letters,m,4707;
and M.C.Caserio,ibid.,l968,5987:
S.H.Smallcombe,R.J.Holland,R.H.Fish
F.J.Randall
B.M.Trost,J.Am.Chem.Soc.,1967.138;
and A.W.Johnson,ibid --a-,
S.Wolfe,P.Chamberlain
1968 2841;
and T.Garrard,m.
J .Chem -a 1976 ,2847. 5. H.Matsuyama,H.Minato P.Bravo
and M.Eobayashi,Bull.Chem.Soc.Jnn.,~,3393:
and C.Ticozzi,J.Orqanometal.Chem
6. H.Schmidbaur,W.Richter,W.Wolf rences
G.Fronza,
.,1978,157,299.
and F.H.Edhler,Chem.Ber
.,=,2649
and refe-
therein.
7. a)T.A.Albright
and E.E.Schweizer,J.Ors.Chem.,~,1168;
b)H.Lischka,J.Am.
Chem.Soc.,m.353. 8. B.M.Trost p.30-31
and L.S.Melvin,Jr.,"Sulfur
and references
9. E.J.Corey,M.Jautelat 10. a)J.B.Stothers chap.4; 11. T.Durst
Ylides",Academic
Press,New
York,-,
therein. and W.Oppolzer,Tetrahedron
"Carbon-13
Letters,m,2325.
NMR Soectroscony",Academic
Press,New
York,=,
b)u.,chap.9. and M.Molin,Tetrahedron
Letters,1975,63;
tens , ibid .a1978 # 467; G.Chassaing,R.Lett
(Received in UK 10 March 1980)
J.F.Biellmann
and J-J-Vi-
and A.Marguet,ibid.,l978,471.
0040-4039/60/0515-2109#02.00/0
CARBON-13 NHB SPECTROSCOPY OF SULFONIUM YLIDES G.BarbareLla, P.Dembech and A.Garbesi Laboratorio C.N.R.,via Tolara di Sotto,89-OZEANO HMXLIA (Bologna)- ITALY
C-13 NMB data for a series of stabilized and unstabilized ylides indicate flattening at the ylidic carbon with respect to the Parent salts. For unst*ilired ylides association between the oarbanionic center and the lithium cation cannot be neglected. Sulfunium yfides are the intermediates in the B/D base-catafysed exchange' and in the methylation2 of sulfonium safts,both reactions being often highly stereoselective.The results of the exchange reaction have been explained on the basis of a pyramidal ylidic carbon and this interpretation is supported by & lb initio calculations .The results of the methylation reaction may be accounted for either by a planar or by a pyramidal ylidic carbona. Direct experimental evi dence on the structure of sulfonium ylides appears to be a necessary step to e& cidate the factors determining the stereosslectivity of these reactions,in anale gy with what has been done for other sulfur compounds3. To our knowledge only a few proton4 and carbon-13' NMR data on stabilized sulfonium ylides (i.e. bearing electron-withdrawing groups attached to the ylidic carbon) have been reported. On the contrary an abundance of data exists on p~~p~ni~ yli.des,for which ex6,7 perimental and theoretical7 evidence indicates a pyramidal and a planar geomg try at phosphorus and carbon respectively. We present here the C-L3 parameters
( 8,
1
a series of stabifised (l-5) and unstabilized
Sew) of the carbanionic carbon for (6-8) sulfonium ylides,which indi-
cate that the ylidic carbon is more flattened (if not planar) than in the corresponding salts. compounds l-5 are either known compounds or were prepared accord 8 ing to established procedures .Compounds 6-8 were obtained directly in the NMR 9 tube at -70°C by treatment of the salts in THY?-d8 with LiCHC12(1.2 eq.) ,After recording the spectra the starting salts were regenerated by quenching with CH30H:decomposition was less than 20%. Spectra were recorded on a Varian FT-80 spectrometer at probe temperature are in Hz and
(25Lt2W
for l-5 and at -7Wc
for 6-8.
3's
b's are in ppsk with respect to cx32CB or TBP-d 8. The accuracy is 2f09
2112
well
as on the general
aspects
of the geometry
of sulfonium
ylides.
References 1. a)G.Barbarella,P.Dembech,A.Garbesi references
therein;
and A.Fava,J.Am.Chem.Soc
.,1975.5883
and
b)G.Barbarella,P.Dembech,A.Garbesi,F.Bernardi,A.Bottoni
and A.Fava,ibid.,1978,200. 2. a)D.M.Roush,E.M.Price,L.K.Templeton,D.H.Templeton =,2971;
b)A.Garbesi,Tetrahedron
3. a)A.J.Abatjoglou,E.L.Eliel Chassaing
and C!.H.Heathcock,ibid.,
Letters,B,547.
and L.F.Kuyper,J.Am.Chem.Soc
and A.Marguet,Tetrahedron,a,l399:
..=,8262;
R.Lett
b)G.
and G.Chassaing,ibid -*
I
-,2705. 4. K.W.Ratts,Tetrahedron
Letters,m,4707;
and M.C.Caserio,ibid.,l968,5987:
S.H.Smallcombe,R.J.Holland,R.H.Fish
F.J.Randall
B.M.Trost,J.Am.Chem.Soc.,1967.138;
and A.W.Johnson,ibid --a-,
S.Wolfe,P.Chamberlain
1968 2841;
and T.Garrard,m.
J .Chem -a 1976 ,2847. 5. H.Matsuyama,H.Minato P.Bravo
and M.Eobayashi,Bull.Chem.Soc.Jnn.,~,3393:
and C.Ticozzi,J.Orqanometal.Chem
6. H.Schmidbaur,W.Richter,W.Wolf rences
G.Fronza,
.,1978,157,299.
and F.H.Edhler,Chem.Ber
.,=,2649
and refe-
therein.
7. a)T.A.Albright
and E.E.Schweizer,J.Ors.Chem.,~,1168;
b)H.Lischka,J.Am.
Chem.Soc.,m.353. 8. B.M.Trost p.30-31
and L.S.Melvin,Jr.,"Sulfur
and references
9. E.J.Corey,M.Jautelat 10. a)J.B.Stothers chap.4; 11. T.Durst
Ylides",Academic
Press,New
York,-,
therein. and W.Oppolzer,Tetrahedron
"Carbon-13
Letters,m,2325.
NMR Soectroscony",Academic
Press,New
York,=,
b)u.,chap.9. and M.Molin,Tetrahedron
Letters,1975,63;
tens , ibid .a1978 # 467; G.Chassaing,R.Lett
(Received in UK 10 March 1980)
J.F.Biellmann
and J-J-Vi-
and A.Marguet,ibid.,l978,471.