Transformations of selenadiazoliumyl-N-unsubstituted methanides (ylides) to new divinyl selenide derivatives and substituted 1,3,5-selenadiazines. Organoselenium systems from azolium 1,3-dipoles

Abstract

4,5-Diphenyl-1,2,3-selenadiazole and 3,5-diphenyl-1,2,4-selenadiazole were alkylated with trimethylsilylmethyl trifluoromethanesulfonate. Quaternisations occurred at N-3 and N-2 respectively. The salts were desilylated to generate transient selenadiazoliumylmethanide (ylide) intermediates. 4,5-Diphenyl-1,2,3-selenadiazol-3-ium-3-ylmethanide, 3, was trapped with dimethyl acetylenedicarboxylate and methyl propiolate in a cycloaddition–rearrangement reaction which gave the pyrazolylvinyl vinyl selenides 6 and 7. 3,5-Diphenyl-1,2,4-selenadiazol-2-ium-2-ylmethanide, 10, ring-expanded in situ to 4,6-diphenyl-2H-1,3,5-selenadiazine, 13.