Reactions of 7-methoxyimino-4-methylchromene-2,8-dione with phosphines. Preparation of N-substituted 7-amino-8-hydroxy-4-methyl-2H-[1]-benzopyran-2-ones

Article abstract of DOI:10.1016/0040-4020(96)00923-4

7-Methoxyimino-4-methylchromene-2,8-dione 2 reacts with triarylphosphines 1(a-d) to give the unexpected 7-arylomino-8-hydroxy-4-methyl-2H-[1]-benzopyran-2-ones 7(a-d) and methyl diarylphosphinates 8(a-d) in high yields. The reaction of 2 with trialkylphosphines 1(e,f) as well as with diphenylphosphine 15 leads to the formation of the N-dialkylphosphinoyl derivatives 11, 12, 14 and the N-diphenylphosphinoyl derivative 19, along with compounds 7(e,f). The methylation of compounds 7a, 7f, 11 and 19 is also studied and reaction mechanisms to explain the formation of the products obtained are suggested.