1997 condensation reactions

condensation reactionsO 0120

10 - 044A Synthetic Entry into Fused Pyran Derivatives Through CarbonTransfer Reactions of 1,3-Oxazinanes and Oxazolidines with CarbonNucleophiles. — Acid-catalyzed condensation of the cyclic carbonnucleophiles (I) with the oxazinanes (II) and the oxazolidine (VII) is found toyield xanthene derivatives. However, with acyclic carbon nucleophiles like ( IV)a Knoevenagel reaction is observed. Condensation of the cyclic nucleophiles(I) with the oxazolidines (IX) results in an unique formation of functionalizedα-tetralones. Reaction of mixtures of cyclic and acyclic nucleophiles with (IIa)leads to benzopyran derivatives of type (VI). — (SINGH, K.; SINGH, J.;SINGH, H.; Tetrahedron 52 (1996) 45, 14273-14280; Dep. Chem., Guru NanakDev Univ., Amritsar 143 005, India; EN)

1