Flash vacuum pyrolysis of stabilised phosphorus ylides. Part 11.1 Unexpected generation and rearrangement of acetyl benzotriazolyl carbene

Seventeen novel α-benzotriazolyl-β-oxo phosphorus ylides 2 have been prepared and characterised. Flash vacuum pyrolysis (FVP) of these generally leads to loss of both R13PO and N2 to give intractable products but, in one case, 2l, extrusion of Bu3P is observed to give 3-acetyl-1,2,4-benzotriazine 6 and 2′-cyanoacetophenone 7, products apparently derived from rearrangement of the initially formed carbene 11, and involving in the latter case a novel 1,3-acetyl migration process.