A method of preparing substituted derivatives of 2,3-dihydro-4H 1-benzopyran

摘要

Substd. derivs. of 2,3-dihydro 6-4H-1-benzopyrane consisting of L- and D-isomers and the racemic mixt. of 2,3-dihydro 6-fluorospiro (4H-1-benzopyrane 4,4'-imidazolidine) 2',5'-dione are made by (a) reaction of p-fluorenol with ethyl 3-bromo propionate; (b) cyclising the prod.; (c) treatment with alkali cyanide, NH4Cl and ammonia; and (d) reaction with an alkali cyanate to form a hydantoin ring. The racemic mixt. obtained is resolved by salt formation with L-1-(1-naphthyl) ethylamine, separation of the adducts by crystallisation and recovery of the L- and D-isomers by extraction with organic solvent.