75785-10-3Relevant academic research and scientific papers
New Light-Induced Reactions of Thioketones with Alkynes
Gotthardt, Hans,Nieberl, Sonja,Doenecke, Juergen
, p. 873 - 885 (2007/10/02)
The reaction of the 1,3-dimethyl-2-thioparabanic acid (1) in the presence of dimethyl acetylenedicarboxylate, induced by visible light (λ ca. 400 nm), leads to formation of the adduct 5, whereas the analogous reaction of 1 with diphenylacetylene (tolan) surprisingly produces the stable spirothiete derivative 7 (57-42percent) and the 1,2-dithiol derivative 8 (22percent).In the same way, tetramethyl-2-thiobarbituric acid (13) reacts with tolan with formation of 14 and 15.On irradiation with yellow light (λ = 589 nm), xanthione (16a) or thioxanthione (16b) combine with tolan to form the spirothiete derivatives 17a (91percent) or 17b (64percent), respectively.On the other hand, the photoreaction of 1 with ethyl phenylpropiolate yields two regioisomeric spirothiete derivatives 21a (26-18percent) and 21b (42-41percent).Without exclusion of oxygen, however, in the last case the reaction proceeds with formation of 21a (15percent) and the 1,2-dithiol derivative 22 (5percent) as well as 1,3-dimethylparabanic acid (24, 40percent).The main product 24 results from a cycloaddition reaction of singlet oxygen to 1 followed by elimination of SO.
