8H-Anhydro-4-hydroxy-2-oxo-1,3-thiazinium Hydroxides as Mesoionic 1,4-Dipoles
摘要:
The previously unknown 8H-anhydro-4-hydroxy-2-oxo-1,3-thiazinium hydroxides (1) were prepared and their 1,4-dipolar cycloaddition behavior was examined. In most cases, elimination of the proton in the 8-position of the mesoionic ring was observed to occur unless extremely reactive dipolarophiles were used. The S,N-ketene acetals were converted to the corresponding alpha-diazo ketones for further study.
The Brønsted acid-catalyzed synthesis of secondary amides from ketones under mild conditions is described via transoximation and Beckmann rearrangement using O-protected oximes as more stable equivalents of explosive O-protected hydroxylamines. This methodology could be applied to highly rearrangement-selective amide synthesis from α-branched alkyl arylketones and performed on a 1-g scale. The presence
New types of bronchodilator agents, bi- and tricyclic nitrogenbridgeheadcompounds with a pyrimidin-4(3H)-one ring, were synthesized and evaluated for bronchodilator activity against serotonin-, histamine-, and acetylcholine-induced spasms in the guinea pig Konzett-Rössler test. The structure-activity relationships are discussed. The effects of some bi- and tricyclic derivatives on the human bronchus