A VERSATILE NEW SYNTHESIS OF ORGANIC-COMPOUNDS WITH CHIRAL METHYL-GROUPS - STEREOCHEMISTRY OF PROTOLYTIC RHENIUM-CARBON BOND-CLEAVAGE IN CHIRAL ALKYL COMPLEXES (ETA5-C5H5)RE(NO)(PPH3)(R)
Academic Article
Overview
Identity
Additional Document Info
Other
View All
Overview
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.
