Nitroolefins in one-flask, tandem. A+B+C coupling reactions producing heterocycles

Abstract

Nitroolefins are shown to be effective Michael acceptor B units in sequential, convenient, multi-gram scale A+B+C coupling in one reaction vessel to produce nitroalkane intermediates that are converted into oxygen and nitrogen heterocycles. The sequence is initiated by enolate nucleophiles (A) and is terminated by aldehydes or acrylate electrophiles (C). The utility of this protocol for rapid assembly of complex structures from simple and readily available components is illustrated by a short total synthesis of a pyrrolizidine alkaloid.