Flash vacuum pyrolyses (FVP) of benzoic 2-methyl-3-furoic anhydride (12) and benzoic 3- methyl-2-furoic anhydride (13) at 550° C and ca. 10–2 Torr both give methylenecyclobutenone (16) and 1-buten-3-yne (17) as the main products. A mechanism involving generation of furan analogues of α-oxo-o-quinodimethane, 10 and 11, from FVP of 12 and 13, respectively, followed by elimination of a CO molecule to give the respective ...