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Reaktionen vinyloger Oxycarbene mit Methanol
Author(s) -
Hömberger Günter,
Kirmse Wolfgang,
Lelgemann Rudolf
Publication year - 1991
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19911240826
Subject(s) - chemistry , methanol , sodium methoxide , carbene , medicinal chemistry , protonation , demethylation , dimethyl ether , methoxide , ion , organic chemistry , catalysis , biochemistry , gene expression , dna methylation , gene
Reactions of Vinylogous Oxycarbenes with Methanol The carbenes 16 and 30 were generated in methanol/sodium methoxide by photolyses of 2‐methylchromone tosylhydrazone ( 14 ) and 3,5‐dimethoxy‐4,4‐dimethyl‐2,5‐cyclohexadienone tosylhydrazone ( 28 ), respectively. Neither 16 nor 30 accept methanol at the carbenic site to give products of a formal O – H insertion. Carbene 16 affords 2‐methoxy‐2‐methyl‐2 H ‐1‐benzopyran ( 19 ) by way of the benzopyrylium ion 17 . The same ether was obtained from the independently prepared perchlorate of 17 . Protonation of 30 was followed by demethylation of the delocalized carboxonium ion 31 to give 5‐methoxy‐6,6‐dimethyl‐2,4‐cyclohexadienone ( 33 ) as the only product.