Heterocycles methyl thioglycolate

Heterocycle Synthesis. Methyl thioglycolate is a very interesting building block because the thiol function and the active methylene group are both potential nucleophiles and the ester group is an electrophile. Like other polyfunctional molecules, every functional group may react individually or in combination with the others. This ability has been widely used for the synthesis of sulfur containing heterocycles as exemplified in eqs and 2. ... 

The most versatile method for synthesis of 2-trifluoromethylthiophenes is based on heterocyclizations with the participation of methyl thioglycolate (HSCH2COOMe). For example, 2-trifluoromethylthiophene 116 was formed as a result of condensation of trifluoromethyl-substituted a,p-unsaturated ester 115 and methyl thioglycolate in the presence of a base. 2-Trifluoromethyl- and (perfluoroalkyl)thiophenes were prepared by reaction with a-fluoroalkylacetates in good yields [69]. A similar transformation took place when fluoroalkylpropynoates 117 were treated with methyl thioglycolate under basic conditions [70]. 

In order to study heterocyclic steroid analogues, such as the 7,11-dithiaazasteroid analogues, Fravolini developed the synthesis of new heterocyclic ring systems tri- and tetracyclic 2,1-benzothiazines <82JHC1045>. Intermediate 137 was prepared from 1-methyl-4-oxo-lH-2, -bcnzothiazinc-4(3f/)-onc 2,2-dioxide 37 and thioglycolic acid and could be converted into 6-methyl-4-oxo-3,4-dihydro-2//,6//-thiopyrano[3,2-c][2,l]benzothiazine 5,5-dioxide 138 by cyclization with polyphosphoric acid. The reaction of 138 with dimethyl... 

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