Cycloadditions. 23. The Thermal Reactivity of S-(1-Naphthyl) and S-(9-Anthryl)-2-methyl-2,3-butadienethioates

Article abstract of DOI:10.1002/prac.19943360804

Heating of the S-(1-naphthyl)esters of 2-methyl-2,3-butadiene thioacid and of 2-methyl-4,4-diphenyl-2,3-butadiene thioacid (3a resp. 3b) furnishes mixtures of the Diels-Alder products 5a,b and the cyclobutenone 7 and the naphthol derivative 8, resp.The corresponding S-(9-anthryl)esters 4a,b are not isolable; under the conditions of their synthesis (allenecarboxylic acids 1a u. b, 9-thioanthrol 2b, DCC and DMAP) they isomerise spontaneously to the Diels-Alder products 9.