SYNTHESIS OF 6-CYANO-2,2-DIMETHYL-2H-1-BENZOPYRAN AND OTHER SUBSTITUTED 2,2-DIMETHYL-2H-1-BENZOPYRANS

A practical synthesis of 6-cyano-2,2-dimethyl-2H-1-benzopyran (1) has been developed. This process involves the pyridine-catalyzed condensat ion of 1,1-diethoxy-3-methyl-2-butene (6) with 4-cyanophenol (3) in to luene or xylene at elevated temperatures. The development of this proc ess, including an evaluation of solvents, bases, acid catalysts, and a lternative acetals, along with an improved synthesis of 1,1-diethoxy-3 -methyl-2-butene, is discus se d. Using this method, a variety of othe r substituted 2,2-dimethyl-2H-1-benzopyrans were synthesized.