Benzothiet-2-ones: Synthesis, Reactions, and Comparison with Benzoxet-2-ones and Benzazetin-2-ones

Article abstract of DOI:10.1021/jo00226a022

Benzothiet-2-one (5) is obtained as a neat solid, stable below -20 deg C(-45 deg C in solution), by flash vacuum pyrolysis of benzothiophene-2,3-dione (9).Naphtho<2,3-b>thiet-2-one (21) and naphtho<2,1-b>thiet-1-one (42) are obtained as stable crystalline solids in near-quantitative yields from the corresponding naphthothiophenediones 20 and 41.Naphtho<2,3-b>oxet-2-one (31) and naphtho<2,3-b>azetin-2-one (36) were generated and observed by IR spectroscopy to be stable below -40 deg C and 0 deg C, respectively.The thietones, oxetones, and azetinones undergo rapid ring-opening reactions with methanol to give the corresponding carboxylic acid esters.They undergo thermal CO elimination with concomitant Wolff-type ring contraction to thioketenes (17, 25, 45), ketenes (30), and nitriles (37), respectively.The di-, oligo-, and polymerization of the thietones has been elucidated.Naphtho<2,1-b>thiet-1-one (42) reacts with 1-thiocarbonyl-1H-indene (45) to give cycloaddition product 46.Naphthothietones 21 and 42 react with dicyclohexylcarbodiimide to furnish 2-imino-1,3-thiazin-4-one derivatives 47 and 49.