Regioselective aminobromination of terminal alkenes

The addition of t-butyl N,N-dibromocarbamate (BBC) to a variety of terminal alkenes has been studied. The reaction was spontaneously initiated and proceeded smoothly in refluxing dichloromethane. The N-bromo adducts, formed upon addition, could be reduced in situ with aqueous sodium sulfite to give the corresponding 2-bromo-N-Boc-amines. Immediate deprotection of these compounds with gaseous HCl or p-toluenesulfonic acid afforded 2-bromoamine hydrochlorides or tosylates in pure state and good overall yields. The observed regioselectivity for anti-Markovnikov addition, as proven by NMR and MS, is fully consistent with the radical-chain mechanism proposed for the reaction. (C) 2003 Elsevier Ltd. All rights reserved.