CONVERSION OF 7-METHOXY-3,4-DIHYDRO-2H-1-BENZOPYRAN-2-ONE INTO THE CORRESPONDING DIMETHYL ORTHO ESTER

7-Methoxy-3,4-dihydro-2H-1-benzopyran-2-one 2 was converted into oxy-4 '-methoxyphenyl)-N-Methyl-N-phenylpropanamide 25 and reaction of this with methyl trifluoromethanesulfonate, followed by reaction with sodiu m methoxide, gave 2,2,7-trimethoxy-2H-1-benzopyran 1a in 55% overall y ield from 25. A similar methylation/methoxide sequence using oxy-4'-me thoxyphenyl)-N-methyl-N-phenylpropanamide 18 gave a mixture which cont ained trimethyl 3-(2'-benzyloxy-4'-methoxyphenyl)orthopropanoate 20a a nd reaction of this mixture with a solution of sodium in tert-butanol gave a product in which 2,2,7-trimethoxy-2H-1-benzopyran 1a was detect ed, but not isolable. (C) 1997 Elsevier Science Ltd.