Regio- and Stereoselective Nucleophilic Substitutions of Chiral Allylic Alcohol Rhenium Complexes

The nucleophilic substitution by alcohols, thiols, allyl silane, or triphenylphosphane of the hydroxy group of an allylic alcohol complexed to a chiral rhenium salt leads to the corresponding ethers, thioethers, 1,5-dienes, and phosphonium salts in high yields [Eq. (1)]. The high regioselectivity of these reactions was unambiguously established by means of a deuterated ligand or with substituted allylic alcohols and any allylic rearrangement reaction was excluded. The reaction of the separate diastereoisomeric rhenium complexes derived from 3-buten-2-ol established that this substitution is stereospecific with overall retention of configuration. Nu = OR, SR, +PPh3 [BF4]−, CH2CHCH2, OAc; R, R′ = H, H; H, CH3; CH3, H.