A new method for cyclodehydration of o-hydroxyaryl-β-ketols to 4-chromanones using HMPT is described. The method has general applicability. It is particularly useful for the cyclisation of labile intermediates as exemplified by the synthesis of cannabinoid synthon, 2-methyl-2-(4-methyl-3-pentenyl)-7-methoxy-4-chromanone.
A. Banerji and Kalena, G. P., “A New Method of Cyclodehydration of 3, 3-Dialkyl-1-Oxo-1-(2-hydroxyaryl) propan-3-ols to 2, 2-Dialkyl-4-chromanones: Synthesis of Cannabinoid Synthon”, Synthetic Communications, vol. 19, pp. 159–166, 1989.