REACTIONS OF -(METHOXYIMINO)-4-METHYL-2H-CHROMENE-2,8(7H)-DIONE WITH PHOSPHORUS YLIDES - SYNTHESIS OF 2-SUBSTITUTED 6-METHYL-8H-[1]BENZOPYRANO[7,8-D]OXAZOL-8-ONES

-(Methoxyimino)-4-methyl-2H-chromene-2,8(7H)-dione (3) reacts with pho sphonium salts 1a-c, 8a, b under phase-transfer catalysis conditions t o afford the title 2-substituted 6-methyl[l]benzopyranooxazol-8-ones 5 a c, 10a, b, respectively, along with compound 6, instead of the expec ted Wittig reaction products. However, the reaction of 3 with the stab le phosphorus ylides 11a-c in addition to the corresponding benzopyran ooxazoles 12a c and compound 6 affords in the last case compound 16 as well according to a sequence involving a n initial Wittig reaction be tween 11c and 3.