Electrochemically initiated, intramolecular anionradical cyclobutanations of bis(enones) and related substrates are presented. The formation of novel anionradical Diels–Alder adducts in minor amounts is also observed. Total yields of pericyclic products, which include both cis- and trans-cyclobutanes and a single Diels–Alder adduct, are generally high (51–88%), with electrocatalytic factors in the
Dramatic effects of the electrolyte cation on the selectivity of electroreductive cycloaddition reactions of bis(enones)
作者:Greg A.N. Felton、Nathan L. Bauld
DOI:10.1016/j.tetlet.2004.09.094
日期:2004.11
The nature of the electrolyte cation (Li, Na, K, Ag, Mg, Ba) exerts a dramatic effect upon the diastereoselectivity of the intramolecular cyclobutanation reactions of several bis(enones). The formation of cis as against trans cyclobutanes is strongly favored by magnesium ions, presumably via a chelation effect, and becomes exclusive in the case of barium. The latter ion has the additional surprising effect of enhancing the amount of Diels-Alder cycloaddition as opposed to cyclobutanation. (C) 2004 Elsevier Ltd. All rights reserved.