Preparation of heterocyclic compounds from alpha-oxoketene O,N-acetals

摘要

alpha-Oxoketene O,N-acetals 1 act as nucleophiles and electrophiles, and are demonstrated as good starting materials for the preparation of various heterocyclic compounds. They are prepared from beta-oxothiono esters 2, which are easily prepared from carbon disulfide,in only mixing with primary amine in the presence of triethylamine. Acetals 1 are converted to pyrrolidine-2, 5-diones 3, 1, 6-naphthyridine-2,5(1H,6H)-diones 4,1,2,3,4-tetrahydro-2-pyridinones 5, piperidine-2,6-diones 6, pyrroles 7, 2H-1,2-oxazine-2,4(3H)-diones 8, and 4H-pyran-4-one 12 by the reaction with electrophiles. On the other hand, acetals 1 also react with nucleophiles to yield pyrazoles 19, isoxazoles 22, and pyrimidines 24. beta-Oxothiono esters 2 are also good substrates for the preparation of 3-ethoxypyrazoles 25, 3-ethoxyisoxazoles 28, and 4-ethoxypyrimidines 29.