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Thia-Diels-Alder reactions of hetaryl thioketones with non-activated 1,3-dienes

Grzegorz Mloston, Paulina Grzelak, Anthony Linden, Heinz Heimgartner
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Abstract


Abstract

Dihetaryl thioketones substituted with thiophen-2-yl and seleophen-2-yl rings react as superdienophilic reagents with non-activated 1,3-dienes such as 2,3-dimethylbuta-1,3-diene, cyclopentadiene and mixtures of isomeric hexa-2,4-dienes to produce the expected 2H-thiopyrans in good to excellent yields. In the latter case, the corresponding cis-3,6-dihydro-3,6-dimethyl-2,2-dihetaryl-2H-thiopyrans are formed as the sole products in a stereoconvergent thia-Diels-Alder reaction. A step-wise mechanism via delocalized intermediate diradicals is postulated to rationalize the observed reaction course. Treatment of 3,6-dihydro-4,5-dimethyl-2,2-di(thien-2-yl)-2H-thiopyran with excess mCPBA at room temperature leads to the oxidation of both the C=C bond and the sulfur atom in the six-membered ring.


Keywords


thia-Diels-Alder reactions, thioketones, 3,6-dihydro-2H-thiopyrans, reaction mechanisms, cyclic sulfones

Full Text: PDF Supplementary File(s): M-351-supplementary files-submitted (568KB)


 

 

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