Enantioselective Synthesis 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
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The di(allyl) sulfide complexes [(5-C5H5)Re(NO)(PPh3)(S(CH2CR=CR2)2)]+TfO (4+TfO; R/R = a, H/H; b, CH3/H; c, H/CH3) and t-BuOK (THF, 80 C) give thiolates (5-C5H5)Re(NO)(PPh3)(SCH(CR2CR=CH2)-CR=CR2) (5ac, 9590%) as 93:7, 98:2, and 93:7 mixtures of SS,RR/SR,RS Re,SC diastereomers. Pure enantiomers (S)-4ac+BF4 give 5ac as 93:7, 99.3:0.7, and 97:3 SS/SR mixtures (8579%). Reactions with MeOTf yield [(5-C5H5)Re(NO)(PPh3)(S(Me)CH(CR2CR=CH2)CR=CR2)]+TfO (9589%), which are treated with EuN+CN to give MeSCH(CR2CR=CH2)CR=CR2(8ac, 6758%; 92:8, >99:<1, 96:4 S/R from (S)-4ac+BF4) and (5-C5H5)Re(NO)(PPh3)(CN) (9, 9378%; >98% ee). Complex (S)-9 can be recycled to (S)-4ac+BF4in 23 steps. Analogous sequences with 5a,b and PhCH2 I give [(5-C5H5)Re(NO)(PPh3)(S(CH2Ph)CH(CR2CR=CH2)CR=CR2)]+I (9779%) and PhCH2SCH(CR2CR=CH2)CR=CR2 (11a,b, 8277%; 93:7, >99:<1 S/R from (s)-4a,b+BF4). Similar S(CH2CCCH3)2 (d) and S(CH2CH=CHR)2 (E; R = e, CH3; f, C(CH3)3; g, C6H5) complexes give thiolates 5dg as comparable Re,SC diastereomer mixtures. However, 5eg contain new SCC stereocenters, and only 5f gives high selectivity (89:11). The pentamethylcyclopenladienyl complex 4a-Me5+TfO yields 5a-Me5 of opposite stereochemistry (7:93 SS,RR/SR,RS). Crystal structures of (S)-4a+SbF6- (triclinic, a 9.800(2), b 10.516(2), c 16.152(3), 93.20(2), 107.16(2), 81.57(2), (SS)-5a (monoclinic, a 9.881(2), b 12.483(3), c 10.877(2), 100.23(2)), (SRR,RSS)-5f (triclinic, a 9.578(3), b 14.019(5), c 15.999(4), 93.22(3), 97.83(3), 107.63(3)), and (SR,RS)-%a-Me5 (monoclinic, a 8.780(2), b 17.379(4), c 20.801(3), 92.49(2)) establish the configurations given above. The mechanism of diastereoselection is analyzed in detail. 1995, American Chemical Society. All rights reserved.
Journal of the American Chemical Society
author list (cited authors)
Cagle, P. C., Meyer, O., Weickhardt, K., Arif, A. M., & Gladysz, J. A.
complete list of authors
Cagle, Phillip C||Meyer, Oliver||Weickhardt, Konrad||Arif, Atta M||Gladysz, JA