This work reports a thiophane-catalyzed dibromination of olefins using NBS as the sole bromine source, wherein a new type of catalytic umpolung strategy of N-bromoimides is revealed. The mechanistic investigation revealed that in situ generated 2,3-dihydrothiophene was the actual catalyst, which was responsible for the catalytic umpolung of NBS.

Abstract

A thiophane-catalyzed dibromination of olefins using NBS as the sole bromine source has been developed, providing a low-cost and mild methodology for preparing vicinally dibrominated compounds from electron-neutral or -deficient alkenes. The mechanistic investigation showed that 2,3-dihydrothiophene generated in situ from the reaction of thiophane with NBS was the actual catalyst, which reversed the polarity of NBS to yield bromide ion.