Thiazolo indol-3-ones

A straightforward synthesis of this system involves the addition of mercaptoacetic acid or its ester across the double bond of the azomethine linkage. 3,3-Dimethyl-2-ethoxycarbonyl-l-indolene (245) reacts with appropriate mercaptocaids (or esters) to give the corresponding thiazolo[3,2- ]indol-3(2//)-ones (246) (74LA206) (Scheme 60). 

Thiazolo[ 3,2-z indoles C3NS-C4N-C6. Treatment of the indole derivative (167) with thionyl chloride unexpectedly gave the thiazolo[3,2-a]indol-3(2//)-one (168), for which a possible mechanism has been suggested. ... 

A mixture of 2.7 g 8-(methylsulfanyl)-6,8-dihydro-7 f-[l,3]thiazolo[5,4-e]indol-7-one (11 mmol), 3.0 g activated zinc, 41 mL acetic acid, and 41 mL THF was heated at 60-65°C for 3.5 h. The gray-green mixture was filtered through a sintered glass funnel containing a 0.5-inch pad of Celite, and the pad was washed with 40 mL hot THF/acetic acid (1 1). Water (200 mL) was added to the filtrate, and the pale yellow mixture was stirred for 10 min. The resulting solid was isolated by filtration, washed with 25 mL water, and dried under vacuum at 70°C to furnish 1.05 g 6,8-dihydro-7Ff-[l,3]thiazolo[5,4-e]indol-7-one as a pale yellow solid, in a yield of 49%. 

Synthesis of Heterocyclic Compounds. Thionyl chloride and pyridine at elevated temperatures convert diarylalkenes, styrenes, and cinnamic acids to benzo[i>]thiophenes and adipic acid to 2,5-bis(chlorocarbonyl)thiophene. Additional heterocycles which have been prepared include thiazolo[3,2-a]indol-3(2//)-ones, oxazolo[5,4- /]pyrimidines, and 1,2,3-thiadiazoles. Treatment of 1,2-diamino aromatic compounds with thionyl chloride gives good yields of fused 1,2,5-thiadiazoles. ... 

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