Reactions of 7‐(Methoxyimino)‐4‐methyl‐2 H ‐chromene‐2,8(7 H )‐dione with Phosphorus Ylides. Synthesis of 2‐Substituted 6‐Methyl‐8 H ‐benzopyrano[7,8‐ d ]oxazol‐8‐ones

7‐(Methoxyimino)‐4‐methyl‐2 H ‐chromene‐2,8(7 H )‐dione ( 3 ) reacts with phosphonium salts 1a – c , 8a , b under phasetransfer catalysis conditions to afford the title 2‐substituted 6‐methylbenzopyranooxazol‐8‐ones 5a – c , 10a , b , respectively, along with compound 6 , instead of the expected Wittig reaction products. However, the reaction of 3 with the stable phosphorus ylides 11a – c in addition to the corresponding benzopyranooxazoles 12a – c and compound 6 affords in the last case compound 16 as well according to a sequence involving an initial Wittig reaction between 11c and 3 .