Titanium tetraisopropoxide promoted reactions for the synthesis of substituted coumarins

Substituted coumarins are synthesized by the reaction of salicylaldehyde derivatives with malonitrile, isopropyl cyanoacetate or diisopropyl malonate promoted by Ti(O-i-Pr) 4 . When i-PrOH is used as a solvent, these reactions proceeded by the catalytic amount of Ti(O-i-Pr) 4 (~0.1 equivalent).