Synthetic utility of biomimicking vanadium bromoperoxidase and n-tetrabutylammonium tribromide (TBATB) in organic synthesis

Nature has established a broad spectrum of methods to introduce halogen atoms in organic compounds. Recent developments have revealed that haloperoxidases are one of the major sources responsible for incorporating bromines to produce bromoorganics in nature. Pioneering studies of numerous researchers have unravelled the details of haloperoxidases, mainly vanadium dependent enzyme bromo- and iodo-peroxidases, including reaction mechanism, kinetics and especially biomimicking studies. In this review, we initially have described the scope of biomimicking vanadium bromoperoxidase in producing the bromonium ion and its further utilisation in conducting oxidative bromination or cleavage of various organic molecules. Moreover, by biomicmicking, the synthesis of OATB and the synthetic utility of various organic ammonium tribromides (OATBs) have been discussed. Among such OATBs, n-tetrabutylammonium tribromide (TBATB) has been explored for bromination of organic molecules as well as in the facile removal of several protecting groups and as a potential catalyst in various synthetic transformations. This review attempts to compile a myriad of reactions concerning the catalytic activity of vanadium bromoperoxidases and the usefulness of various OATBs, particularly with special emphasis on TBATB in various organic transformations.

Synthesis of 2-chromanone-fused [3.2.0] bicycles through a phosphine-mediated tandem [3 + 2] cyclization/intramolecular Wittig reaction

A phosphine-mediated tandem [3 + 2] cyclization/intramolecular Wittig reaction of alkynone is described. 2-Chromanone-fused bicyclo[3.2.0]heptenones were synthesized in moderate to high yields with remarkably high regio- and diastereoselectivities.