Intramolecular hydroxycarbene C–H-insertion: The curious case of (o-methoxyphenyl)hydroxycarbene

• Dennis Gerbig,
• David Ley,
• Hans Peter Reisenauer and
• Peter R. Schreiner

Beilstein J. Org. Chem. 2010, 6, 1061–1069, doi:10.3762/bjoc.6.121

• Dennis Gerbig David Ley Hans Peter Reisenauer Peter R. Schreiner Institut für Organische Chemie, Justus-Liebig University Giessen, Heinrich-Buff-Ring 58, 35392 Giessen, Germany 10.3762/bjoc.6.121 Abstract The first C–H insertion of a hydroxycarbene species in the gas phase has been observed

• experimentally by means of high vacuum flash pyrolysis (HVFP) and subsequent matrix isolation: (o-Methoxyphenyl)glyoxylic acid gives non-isolable (o-methoxyphenyl)hydroxycarbene upon pyrolysis at 600 °C, which rapidly inserts into the methyl C–H bond. The insertion product, 2,3-dihydrobenzofuran-3-ol, was

• produced instead; however, the carbene cannot be observed under these conditions. Thermal decomposition of (o-methoxyphenyl)glyoxylic acid in refluxing xylenes does not give the insertion product but yields o-anisaldehyde. This unanticipated outcome can be rationalized by protonation of the hydroxycarbene