The Preparation of Nonracemic Secondary α-(Carbamoyloxy)alkylzinc and Copper Reagents. A Versatile Approach to Enantioenriched Alcohols
摘要:
GRAPHICSChiral alpha-(carbamoyloxy)alkyllithium reagents, prepared using Hoppe's sBuLi/(-)-sparteine methodology, were transmetalated with ZnCl2. Further transmetalation with CuCN with overall retention of configuration gave chiral species that reacted with various electrophiles to give enantiomerically pure alcohols after deprotection. A short, highly efficient synthesis of an industrially relevant pheromone, japonilure, illustrates the value of the methodology.
Determination of the Effect of Cation−π Interactions on the Stability of α-Oxy-Organolithium Compounds
摘要:
Sn-Li exchange equilibria have allowed the quantification of the stabilizing effect of cation-pi interactions in organolithium chemistry. Stabilization energy data on the effect of Li-pi complexation of an aromatic ring or a C=C double bond in organolithium compounds are presented. The amount of stabilization gained by complexation of the Li atom with a pi system in alpha-oxy-organolithium compounds is quite comparable to the one observed in systems containing Li-N or Li-O interactions.