The pyrolysis of fur-2-ylmethyl vinyl ether and its next highest homologue, the propenyl ether, is described. Products from two reaction mechanisms are observed, namely a 3substituted 2-methylfuran from an electrocyclic mechanism, and 1, Z-di-(fur-Z-yl)-ethane and furylpropanal from a biradical mechanism.
In the course of investigations that led to the synthesis of dendrolasin [l] [2], the fact that the diene ether 1 of fur-2-ylmethanol could be induced to rearrange thermally quite easily was contrasted with the stability of its vinyl ether (2) [3]. In this paper, results from the pyrolysis of fur-2-ylmethyl vinyl ether (2) are described.
Results. -As reported by Watanabe & Conlon [3], fur-2-ylmethyl vinyl ether (2) can be made in 30-35y0 yield by mercuric acetate-catalyzed ether exchange from fur-2-ylmethanol and ethyl vinyl ether. All attempts to raise the yield by varying the conditions were unsuccessful. Preliminary experiments with the ether pyrolyzed in the injection chamber of a gas chromatograph showed that it was little changed below 350", but that at 370-400", a number of products was formed. A typical chromatogram with the injector temperature at 400" showed about 25% starting material (2), together with the following major products: 2-(2-methylfur-3-yl-ethanal (3) (25y0), 3-(fur-2-yl-propanal (4) (35%), and some fur-2-ylmethanol, together with about 5% of I,Z-di-(fur-Z-yl)-ethane (5). Traces of unidentified products were also observed.