The [3 + 2] cycloaddition reaction of thiazole carbene-derived C-C-Se 1,3-dipoles: a concise and highly efficient strategy for the construction of multifunctional dihydroselenophenes and selenopheno[2,3-b]pyrazines.

The first study on the reaction of C(+)-C-Se(-) 1,3-dipoles with electron-deficient alkenes and alkyne is reported. 2-Arylselenocarbamoylthiazolium inner salts, the unique thiazole carbene-derived C(+)-C-Se(-) 1,3-dipoles, reacted efficiently with methoxycarbonylallenes or dimethyl acetylenedicarboxylate to produce dihydroselenophenes or selenopheno[2,3-b]pyrazines, respectively, in high yields. Both reactions probably proceeded via a [3 + 2] cycloaddition of C(+)-C-Se(-) 1,3-dipoles with alkenes or alkyne followed by different transformations of the thiazole-spiro-selenophene intermediates. This work provides a concise and efficient strategy for the construction of multifunctional dihydroselenophenes and selenopheno[2,3-b]pyrazines, which are not easy accessible by other methods.