Journal of the American Chemical Society, Vol.117, No.47, 11730-11744, 1995
Enantioselective Syntheses of Organosulfur Compounds via (2,3)-Rearrangements of Ylides Derived from di(Allyl) and di(Propargyl) Sulfide Complexes - Control of Carbon Configuration by an Easily Resolved and Recycled Chiral Transition-Metal Auxiliary
The di(allyl) sulfide complexes [(eta(5)-C5H5)Re(NO)(PPh(3))(S(CH(2)CR=CR’(2))(2))](4)TfO(-) (4(+)TfO(-); R/R’ = a, H/H; b, CH3/H; c, H/CH3) and t-BuOK (THF, -80 degrees C) give thiolates (eta(5)-C5H5)Re(NO)(PPh(3))(SCH(CR’(2)CR=CH2)CR=CR’(2))(5a-c, 95-90%) as 93:7, 98:2, and 93:7 mixtures of SS,RR/SR,RS Re,SC diastereomers. Pure enantiomers (S)4a-c(+)BF(4)(-) give 5a-c as 93:7, greater than or equal to 99.3:0.7, and 97:3 SS/SR mixtures (85-79%). Reactions with MeOTf yield [(eta(5)-C5H5)Re(NO)(PPh(3))(S(Me)CH(CR’(2)CR=CH2)CR=CR’(2))](+)TfO(-) (95-89%), which are treated with Et(4)N(+)CN(-) to give MeSCH(CR’(2)CR=CH2)CR=CR’(2) (8a-c, 67-58%; 92:8, >99:<1, 96:4 S/R from (S)-4a-c(+)BF(4)(-)) and (eta(5)-C5H5)Re(No)(PPh(3))(CN) (9, 93-78%; >98% ee). Complex(S)-9 can be recycled to (S)-4a-c(+)BF(4)(-) in 2-3 steps. Analogous sequences with 5a,b and PhCH(2)I give [(eta(5)-C5H5)Re(NO)(PPh(3))(S(CH(2)Ph)CH(CR’(2)CR=CH2)CR=CR’2)]I-+(-) (97-79%) and PhCH(2)SCH(CR’(2)CR=CH2)CR=CR’(2) (11a,b, 82-77%; 93:7, > 99:< 1 S/R from (S)-4a,b(+)BF(4)(-)). Similar S(CH2C=CCH3)(2) (d) and S(CH2CH=CHR)(2) (E; R = e, CH3; f, C(CH3)(3); g, C6H5) complexes give thiolates 5d-g as comparable Re,SC diastereomer mixtures. However, 5e-g contain new SCC stereocenters, and only 5f gives high selectivity (89:11).
Keywords:RAY CRYSTAL-STRUCTURES;ASYMMETRIC INDUCTION;ORGANOMETALLIC COMPOUNDS;SIGMATROPIC REARRANGEMENTS;DYNAMIC BEHAVIOR;SULFUR YLIDES;RHENIUM;REACTIVITY;GENERATION;ELECTROPHILES