The magnesium bromide diethyl etherate (MgBr2· OEt2)-methyl sulfide (Me2S) system is useful for the mild and chemo-selective deprotection of p-methoxybenzyl (PMB) ether. Lewis acid for catalysis of Diels-Alder reactions of homochiral 2-sulfinylmaleates with cyclopentadiene. Magnesium bromide diethyl etherate is used in the synthesis of silicon-containing azole derivatives.