A method for the synthesis of γ-butyrolactones 6 is described in which the key step is a free- radical cyclization of α-bromoacetals 4 to 2-alkoxytetrahydrofurans 5 in 54–93% yield induced by activated chromium (II)-acetate. Four new methods have been developed in order to activate the transition metal. Two of them require only catalytic amounts of chromium (II)-acetate, because it can be regenerated in situ chemically or electrochemically. The ...
