Reaction of allyl and benzyl alcohols, and their toluene-p-sulphonates, with furan

Abstract

2-Allyl- and 2-benzyl-furans may be prepared from allyl or benzyl alcohols which are capable of generating stable carbonium ions. The tosyl derivative of the alcohol is refluxed with furan in acetonitrile. The reaction is catalysed by lithium perchlorate. Some alcohols can react directly with furan under acidic conditions. Alcohols investigated include 2-benzylallyl alcohol (8), E-α-methylcinnamyl alcohol (2) and its p-nitro- and p-methoxy-derivatives, (1) and (3), benzyl alcohol, p-nitrobenzyl alcohol, and p-methoxybenzyl alcohol. Both geometrical isomers of α-methyl-p-nitrocinnamyl alcohol, (1) and (13), were prepared and their stereochemistry established by chemical and spectroscopic methods. Only the E-isomer (1) reacts with furan, however. The mechanism of the reaction is discussed and attempts to achieve a 1,3-dipolar cycloaddition are described.