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[摘要]：Flash vacuum pyrolyzes (FVP) of benzoic 3-methyl-2-benzofurancarboxylic anhydride (12) and benzoic 2-methyl-3-benzofurancarboxylic anhydride (13) at 550 癈 and ca. 10-2 torr both give methylenebenzocyclobutenone (21) as the major product and indenone (22) as the minor one. A mechanism involving generation of a-oxo-o-quinodimethane 11 as the primary pyrolysis product from FVP of 13, followed by elimination of a CO mol. to give carbene 24, which undergoes a vinylcarbene-cyclopropene rearrangement and a ring contraction of the resulting carbene 23, is proposed to account for the obsd. results. The proposed mechanism is further supported by a deuterium-labeling study on FVP of (2-benzofuryl)methyl-a,a-d2 benzoate (28-d2). |
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