Studies in sigmatropic rearrangement: synthesis of 4-aryloxy-methylene-1,7-dimethyl-1,2,3-trihydropyridino-[3,2-c]pyran-5-ones

A number of 4-[N-4′-aryloxy but-2-ynyl N-methyl amino-6-methyl pyran-2-ones (4a–g) have been prepared in excellent yields from N-(1-aryloxy-but-2-ynyl)-N-methyl amine (3) and 4-tosyloxy-6-methyl-pyran-2-one (2). Thermal rearrangement of compounds 4(a–g) gave 4-aryloxy-methyl-1,7-dimethyl-1,2-dihydropyridino-[3,2-c] pyran-5-ones (6) and/or 4-aryloxymethylene-1,7-dimethyl-1,2,3-trihydropyridino-[3,2-c] pyran-5-ones (5).