The synthesis of some chromans via o-quinone-methide intermediates

The inverse-electron demanded Diels-Alder reaction of 2-N,N-dimethylaminome thyl-3,4-dimethyl-phenol (5) with styrene and substituted styrenes was inve stigated. With styrene 2-phenyl-6,7-dimethylchroman (7,R=H) was obtained in 58% yield. With 2-, 3- and 4-methylstyrenes, 2-(2'-,3'- and 4'-methylpheny l)-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'-a nd 4'-chlorophenyl)-6,7-dimethyl-chromans (7, R=2-, 3, and 4-Cl) were obtai ned in 16, 20, and 28.5% yields. respectively. With 4-bromostyrene, 2-(4'-b romophenyl)-6,7-dimethylchroman (7,R=4-Br was obtained in 35% yield. In all pyrolysis no quinone-methide dimer (8) was encountered.