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)

Metal complexes of weakly coordinating anions. Precursors of strong cationic organometallic Lewis acids

“…Some mechanistic investigations on the reaction of metal alkyl complexes with strong acids have been undertaken. 98,99 The protonation of the optically active CpRe*(NO)(PPh3)R* by HBr proceeds with retention of configuration at both carbon and rhenium,98 which "can be visualized as a net addition of HX across the rhenium-carbon cr-bond".…”

Low-valent Organorhenium Compounds

“…189 190 A clever synthesis of chiral methyl groups takes advantage of the stereoselective hydride abstraction and nucleophilic addition reactions at chiral rhenium alkyl and benzylidene complexes. 191 The stereochemical outcome requires retention of configuration at carbon in the HBr cleavage step.…”

Synthetic applications of enantioselective organotransition-metal-mediated reactions

“…For example, reaction of optically pure 35 with a chiral nitrile proceeds with overall retention of configuration at rhenium (eq ll).64 Alkylation of alkylidene and acetylide complexes is also readily observed (eq 12) .65 Gladysz has been primarily interested in determining the mechanistic aspects of stereospecific hydride abstraction and various asymmetric rhenium to carbon inductions that occur in this system.66 Some interesting synthetic applications of his mechanistic work involving deuterium include the development of a synthon for a chiral, pyramidal methyl carbenium ion (Figure 16). 67 Additionally, chiral rhenium-ketone complexes can be used to give optically active alcohols in high enantiomeric excess (eq 13).68 Chiral iron-alkyl complexes (36) and chiral ironcarbene complexes (37) have been used to effect asymmetric cyclopropanation of olefins (Figure 17). 69 Alkylation of halo compounds 38 and olefin derivatives 39 can proceed with a significant degree of asymmetric induction, especially when the steric bulk of the iron center is increased by using tri(O-biphenyl) phosphite (OBP) rather than triphenylphosphine (Table 16).…”