THE SYNTHESIS OF SOME CHROMANS VIA o-QUINONE-METHIDE INTERMEDIATES

Abstract

The inverse-electron demanded Diels-Alder reaction of 2-N,N-dimethylaminomethyl-3,4-dimethyl-phenol (5) with styrene and substituted styrenes was investigated. With styrene 2-phenyl-6,7-dimethyl-chroman (7,R = H) was obtained in 58% yield. With 2-, 3- and 4-methylstyrenes, 2-(2′-,3′- and 4′-methylphenyl)-6,7-dimethyl-chromans (7,R = 2-, 3- and 4-CH3) were obtained in 21.7, 25, and 38% yields, respectively. With 2-,3- and 4-chlorostyrenes, 2-(2′-,3′-and 4′-chlorophenyl)-6,7-dimethyl-chromans (7, R = 2-, 3, and 4-Cl) were obtained in 16, 20, and 28.5% yields, respectively. With 4-bromostyrene, 2-(4′-bromophenyl)-6,7-dimethyl-chroman (7,R = 4-Br was obtained in 35% yield. In all pyrolysis no quinone-methide dimer (8) was encountered.