Preparation of 2,3-Dimethylene-2,3-dihydrobenzofuran by the Flash Vacuum Pyrolysis of (2-Methyl-3-benzofuryl)methyl Benzoate

Article abstract of DOI:10.1021/jo00372a020

Pyrolysis of (2-methyl-3-benzofuryl)methyl benzoate (7) gives a 30percent yield of two dimers of 2,3-dimethylene-2,3-dihydrobenzofuran (4), a <4 + 2> dimer 12 and a <4 + 4> dimer (13), in a ratio of 4.1 to 1.It is shown, by low-temperature 1H-NMR spectroscopy, that the primary pyrolysis product from 7 is 4, which forms 12 and 13 upon warming.The structure of the <4 + 2> dimer 12 is confirmed by a deuterium-labeling experiment.Compound 4 can be trapped with methyl acrylate to form a 3.0 to 1 ratio of two Diels-Alder adducts.