Synthetic applications of intramolecular insertion in arylcarbenes. V o-Benzyl, phenylamino, phenoxy and phenylthio phenylcarbenes

Abstract

The 2-(XC₆H₄)-substituted phenylcarbenes in which X = CH₂, NH, O and S have been generated and pyrolysed in the gas phase at low pressure. When X = CH₂ or NH, the main reaction is simple insertion into the adjacent o-position of the XC₆H₅ ring to give dihydroanthracenes and dihydroacridines respectively. The use of substituents shows that no spiro diene rearrangement is involved in the case X = NH. For X = O or S, on the other hand, the carbene inserts into the π-system ofthe XC₆H₅ ring and expansion occurs to give benzo[b]cyclohepta[d]furans and thiophens.