Model studies related to the cofactor of oxomolybdoenzymes. Part 2. Quinoxalin-2-yl-ethane- and-ethene-1,2-dithiols

Abstract

2-Hydroxy-2-phenylethyl and-2-quinoxalin-2-ylethyl N,N-dimethyldithiocarbamates are cyclised to 4-aryl-1,3-dithiolane-2-thiones, (8b) and (10), and these could be dehydrogenated to the corresponding dithioles, (7b) and (11), from which the arylethene-1,2-dithiolates could be released by alkaline hydrolysis. MCPBA then TFAA treatments of cyclohexanone, acetophenone, and quinoxalin-1-yl methyl ketone ethane-1,2-dithiol thioacetals and of cyclohexanone 1, 2-diphenylethane- 1, 2-dithiol thioacetal produces the corresponding rearranged dihydro-1,4-dithiins (14a), (17), (19), and (14b) respectively. Only in the cases of (14a) and (14b) could the desired reductive cleavages to generate 1,2-dithiolate, be achieved. Under reductive methylation conditions the pyrazine ring of (19) was selectively reduced, release of 1,2-dithiolate from the product (20b) now proving possible. 2-Acetylquinoxaline gave a 1,3,2-oxaphospholane 2-sulphide on treatment with Lawesson's reagent.