5965
J . A m . Chem. SOC.1989, 1 1 1 , 5965-5961
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Table I. Asymmetric Oxidation of Prochiral Sulfides to Sulfoxides Using Camphorsulfonyloxaziridine 3 a t 20 “ C
+ R-S-R‘
3a-b
entry I
solvent
sulfoxide ~-ToI-s(o)-cH~~~~
CHzCIz
3 4
p-Tol-S(0)-n-Bdd
5
p-Tol-S(0)-i-Prf,d
CHzC12
64 (S) [ l ] 70
CC14
6 7
d
(5’) [ l ] 80 ( S ) [40] 22 ( S ) [ l ] 70
CH2C1, CCl, CCI,
CHZCI,
+ (-)-4
or (-)-5
% ee (configuration) [time (h)] % yield“ 3a (X = H ) 3b (X = CI) 28 26 11 8 11 8 23
cc1,
2-
R-S(0)-R’
( S ) [18] 9 0 ( S ) [ l ] 70 ( S ) [18] 90 ( S ) [40] 23
( S ) [ I ] 60 ( S ) [4] 95 ( S ) [ l ] 90 ( S ) [3] 9 0 5 4 ( S ) [ l ] 95 66 ( S ) [6] 95 92 (5’) [IS] 9 0 62 95 61 84
[.IZ00 (in acetone)
modified Sharplessb 96 ( R ) e
-139.0
(C
1.6)
-162.3
(C
3.2)
-1 19.0 -131.6
(C
(C
3.0) 1.1)
95 ( R ) f
-138.8
(C
1.2)
86 (R)g
20 ( R ) b 63 ( R ) b
Ph-S(O)q f.d
8
95 ( S ) [ I ] 9 0
9 CCI, 73 ( S ) [ l ] 80 95 ( S ) [48] 6 0 70 (R)g 85 ( S ) [48] 60 -262.4 ( C 1.7) IO Ph-S(0)-CH=CH2d CC14 21 ( S ) [40] 25 94 (S) [48] 65 -170.0 (C 1.5)h 64 (R)g 11 Ph-S(0)CHzC02CH,’.d CC14 23 (S) [40] 18 12 Ph-S(0)CH2C(O)CH,c,d CC14 no reaction 84 (S) [48] 52 -183.2 ( C 1.1) 60 (R)g 13 Ph-S(0)-CH2CNd CCI4 no reaction >95 (S) [48] 45 -170.1 ( C 1.0) 34 (R)g 94 ( S ) [I81 84 +7.1 (c l.O)i 53 ( R ) b 14 (CH,)3C-S(0)CH,C+’ CCI4 66 (5’) [12] 85 Isolated yields. boxidations a t -20 OC for 4-22 h. See ref 6. ‘Ee’s determined using Eu(hfc),. dDetermined by comparison of the rotation to literature values. e Reference 6e. /The sulfoxide enantiomers were separated on a Regis Pirkle covalent phenylglycine H P L C column eluting with 95:5 hexane/isopropyl alcohol. T h e S-sulfoxides were the first to be eluted. See ref 4. EReference 6b. * I n ethanol. ’ In CHCI,.
sulfonyloxaziridines are ideal reagents for the synthesis and study of optically active selenoxides because oxidations can be carried out under anhydrous conditions in the absence of acid.I8 Indeed oxidation of 6 by (-)-3b in CDCI, a t 20 O C affords (-)-(S)-7in 73% ee (95% yield).20 Oxidation a t -60 OC improves the ee to 83%. Interestingly oxidation of 6 by 3b is faster than methyl p-totyl sulfide (
