In the case of coumarin 1h, however, when anhydrous EtOH was used as solvent, the transesterified product 2h′, instead of the expected 3,4-dihydrocoumarin 2h, was obtained in 90% yield (Table [1] , entry 8). Apparently, the cyano group renders 2h labile towards the nucleophilic EtOH. This problem was solved by using anhydrous CH 3 CN or anhydrous THF as the solvent, and 2h was obtained in high yield. The best result was achieved when the reaction was carried out in ...
