A versatile new synthesis of organic compounds with chiral methyl groups: stereochemistry of protolytic rhenium-carbon bond cleavage in chiral alkyl complexes (.eta.5-C5H5)Re(NO)(PPh3)(R) Academic Article uri icon

abstract

  • Reaction of (77 5 -C 5 H 5 )Re(N0)(PPh3)(C0 2 CH 3 ) (1) with (3,5-dimethoxyphenyl)magnesium iodide gives 3,5-di-methoxybenzoyl complex (T? 5 -C 5 H 5 )Re(NO)(PPh 3 )(CCK3,5-C 6 H 3 (OCH3) 2 )) (2, 97%). Reaction of 2 with BH 3 •THF gives 3,5-dimethoxybenzyl complex (T? 5 -C 5 H 5 )Re(NO)(PPh3)(CH 2 (3 ) 5-C 6 H3(OCH 3 ) 2 )) (3, 86%). Reaction of 3 with Ph 3 C + PF 6 ” at -80 °C gives a 62:38 mixture of the sc and ac Re=C geometric isomers (4k, 4t) of 3,5-dimethoxybenzylidene complex [(i7 5 -C 5 H 5 )Re(NO)(PPh 3 )(—CFf(3,5-C 6 H 3 (OCH 3 ) 2 ))] + PF 6 '; workup gives 4t (89%). Reaction of 4t with Li(C 2 H 5 ) 3 BD or NaBD 4 gives addition product (SS,RR)-3-a-dy Optically active (H-H^)-! and (-)-(/?)-l (>98% ee) are similarly treated with (3,5-dimethoxyphenyl)magnesium iodide, BD 3 .THF, and Ph 3 C + PF 6 ' to give (+)-(S)- and (-MT^^t-a-^. Addition of NaBT 4 gives (+)-(SS)- and (—)-(RR)-3-a-d1t1. Reaction with HBr gives (5 1 )- and (/^-dimethoxytoluene-a-^f!, and (+)-(/?)-and (-)-(5)-(77 5 -C 5 H 5 )Re(NO)(PPh 3 )(Br) (retention of configuration at carbon and rhenium). The former are treated with 0 3 to give chiral acetate salts (5)- and (/?)-CFIDTCOO _ Na + of 93% and 86% ee, as established by an enzymatic assay. The mechanisms of these transformations, and the utility of this route to chiral acetic acid, are discussed. © 1987, American Chemical Society. All rights reserved.

author list (cited authors)

  • O'Connor, E. J., Kobayashi, M., Floss, H. G., & Gladysz, J. A.

citation count

  • 34

publication date

  • August 1987