Prodn. of coumarin and derivs.

摘要

Prodn. of coumarins of formula (I) comprises cyclising an aryl 3,3-dialkoxyalkanoate of formula (II) or an aryl 3-alkoxy-acrylate of formula (III), either by:(a) reaction with a Lewis acid in an inert solvent at 0-120 (pref. 20-50) deg C; or (b) gas-phase reaction on a heterogeneous acid catalyst at 200-400 deg C. R1 = H, 1-4C alkyl, 1-4C alkoxy, halo or dialkylamino; R2,R3 = 1-4C alkyl, or R2+R3 = 2-3C alkylene opt. substd. by lower alkyl; R4 = H or 1-4C alkyl.