反应详情

According to EPO 0 076 075 describing the possibilities for preparing Kromakalim 4-cyano-phenol of the formula (I) ##STR4## is reacted with 3-chloro-3-methyl-butyne resulting in propargyl-ether of the formula (IX) ##STR5## which is then subjected to ring closure to produce 6-cyano-2,2-dimethyl-2H-1-benzopyran of the formula (III) ##STR6## The compound of the formula (III) is then converted through 6-cyano-trans-3-bromo-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4-ol to 6-cyano-3,4-dihydro-3,4-epoxy-2,2-dimethyl-2H-1-benzopyran of the formula (V). ##STR7## From the compound of the formula (V) the end-product of the formula (VI) can be obtained by three independent routes.