Fully Substituted Thiophene\nSynthesis via (3 + 2)\nwith Thiadiazoles

A method\nto access highly substituted dihydrothiophenes and the\ncorresponding thiophenes is reported. This strategy complements traditional\nstepwise synthesis by coupling readily accessible bicyclic 1,2,3 thiadiazoles\nwith alkenes in a modular, Rh-catalyzed formal (3 + 2) cycloaddition.\nApplication of this method to an array of novel thiadiazoles generates\ndensely functionalized dihydrothiophenes that can be subsequently\noxidized to the corresponding thiophene products.