P. S. Petrov, V. Kalyazin, N. Somov
Feb 1, 2021
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Journal
Russian Journal of Organic Chemistry
Abstract
1-Bromovinyl and vinyl methyl sulfones undergo 1,3-dipolar cycloaddition reactions with azomethinylides generated in situ from ethyl N-benzylideneglycinates under the action of silver acetate and triethylamine (toluene, 20°C, 48 h) to form ethyl esters of 4-methanesulfonyl-substituted cis-5-arylprolines. The bromo-substituted adducts convert into the corresponding ethyl 5-aryl-1H-pyrrole-2-carboxylates under heating with an excess of DBU in THF or sodium ethylate in ethanol. Heating of the adducts of vinyl methyl sulfone with sodium ethylate in ethanol in sealed ampules at 90°C leads to mixtures of ethyl 5-aryl-1H-pyrrole-2-carboxylates and 5-aryl-2-acetylpyrroles.