Base catalysed intermolecular cyclisation of N-protected o-amino benzaldehyde/acetophenone with phosphorus/sulphur based allenes: facile synthesis of substituted quinolines

Reaction of N-Bz protected o-aminobenzaldehyde or acetophenone with allenylphosphonates in the presence of a simple base leads to quaternary carbon substituted phosphono-quinolines which undergo thermal rearrangement to O-phosphorylated quinolines. The present one-pot reaction involves intermolecular cyclisation, dehydration, and benzoyl group rearrangement followed by a novel phosphoryl group migration. The migration was less facile/not observed in the reactions using allenylphosphine oxides and sulphur based allenes wherein only substituted quinolines were obtained in good yields. X-ray structures have been determined for the key products.