The Gas-Flow Thermolysis of 1-Isobutenyl Alkynyl and 2-Methylphenyl Alkynyl Ketones. Synthesis of Methylenomycin B

Article abstract of DOI:10.1002/hlca.19860690306

The gas-flow thermolysis of 1-isobutenyl alkynyl or 2-methyphenyl alkynyl ketones were found to lead to phenols and cyclopentenones or to naphthols and indanones, respectively.These conversions involve two cyclization processes so far unknown with α-alkynones; they are interpreted as intramolecular additions of an allylic or a benzylic C,H bond to a triple bond which may occur in two directions.In addition, the cyclopentenones formed by the α-alkynone cyclization, a known carbene process yielding 5-rings, were also found.The available evidence ruled out a carbene process yielding 6-rings.The addition process yielding 5-rings was applied to a short (but low yield) synthesis of methylenomycin B.