REACTION OF ALLYLSTANNANES WITH ALPHA,BETA-UNSATURATED ACYLIRON COMPLEXES - STEREOSELECTIVE SYNTHESIS OF CYCLOPENTANE DERIVATIVES

The reaction between allylstannanes and α,β-unsaturated acyliron complexes has been examined. When the reaction is conducted in the presence of Lewis acids, [3 + 2] cycloaddition products are obtained with extremely high degrees of stereoselectivity. If the iron complex is alkylated prior to addition of the allylstannane, products resulting from the Michael addition of allyl anion are obtained. The [3 + 2] cycloadducts contain acyliron and organotin functionalities. The acyliron group is easily converted to the corresponding ester by treatment with N-bromosuccinimide in the presence of alcohols. The tributyltin group can be converted to a hydroxy group by treatment with bromine followed by treatment with peracids and amine bases; this transformation occurs with complete retention of stereochemistry. The high stereoselectivity can be explained by reaction through a synclinal orientation of allylstannane and the acyliron complex. The question of allylation vs cycloaddition has been attributed to the relative reactivity of the intermediate enolate derivatives. © 1990, American Chemical Society. All rights reserved.