Asymmetric deprotonation-substitution of arenetricarbonylchromium(0) complexes: substituent controlled lithiation with the butyllithium-sparteine system

Attempted enantioselective deprotonation of fluorobenzenetricarbonylchromiu m(0) with ca. I equivalent of butyllithium/(-)-sparteine in ether-hexane at -78 degreesC followed by a chlorotrimethylsilane quench gave the racemic o r rho-substituted product. Analogous enantioselective deprotonation of anis oletricarbonylchromium(0), followed by electrophilic quench, gave the 1-(Rp )-substituted complexes in up to 77% yield with 27% e.e., but with methoxym ethoxybenzenetricarbonylchromium(0), (4-triisopropylsilyl-oxymethyl)methoxy methoxybenzenetricarbon and (N-t-butoxycarbonylaniline)tricarbonylchromium( 0), the 1-(Sp)-products were formed in up to 58% yield with 92%;, e.e. The results are explained in terms of coordinative and non-coordinative enantio selective lithiation. (C) 2001 Elsevier Science Ltd. All rights reserved.