The Origins of the Benzotriazole Project, Its Versatility Illustrated by a New -C=CHCH+OEt Synthon, and Novel Syntheses of α,β-Unsaturated Aldehydes and Ketones, Furans, Pyrroles and Allyl Ethers

Abstract

A historical introduction describes the discovery and progress of benzotriazole synthetic methodology. 3-(Benzotriazol-1-yl)-1-ethoxyprop-1-ene (6), readily prepared from 3-(benzotriazo-1-yl)-3-ethoxyprop-1-ene (4) via zinc bromide promoted allylic rearrangement, undergoes lithiation and regiospecific single or double 3-alkylation to give products which undergo (i) hydrolysis to afford α,β-unsaturated aldehydes, (ii) silica gel promoted reverse allylic rearrangement of the benzotriazolyl group, followed by further alkylation and subsequent hydrolysis to furnish α,β-unsaturated ketones, (iii) intramolecular cyclizations to construct pyrroles and furans, and (iv) intermolecular nucleophilic substitution with Grignard reagents to provide allyl ethers.