A Cyclization of β-Arylethylisocyanates to 3, 4-Dihydroisocarbostyrils

抄録

A β-arylethylisocyanate derived from β-(3, 4-methylenedioxyphenyl) (3a)-, β-(3, 4-dimethoxyphenyl) (3b)-, β-(3, 4, 5-trimethoxyphenyl) (3c)- or β-(3-methoxyphenyl) (3d)-propionic acid was treated with anhydrous phosphoric acid at room temperature to give, in moderate yield, 6, 7-methylenedioxy (4a)-, 6, 7-dimethoxy (4b)-, 6, 7, 8-trimethoxy (4c)-, or 6-methoxy (4d)- and 8-methoxy (4d')-3, 4-dihydroisocarbostyrils. In the case of β-(4-benzyloxy-3-methoxyphenyl) (3e)- or β-(3-benzyloxy-4-methoxyphenyl) (3f)-propionic acid, however, only 8-benzyl-7-hydroxy-6-methoxy (4e)- or 5-benzyl-6-hydroxy-7-methoxy (4f)-3, 4-dihydroisocarbostyril, respectively, was obtained in low yield.