Sc(OTf)3-catalyzed diastereoselective synthesis of 3,4-dihydro-4-amino-2H-1-benzopyrans

2,2-Dimethoxypropane reacts with a variety of o-hydroxybenzaldimines in the presence of a catalytic amount of scandium triflate at ambient temperature to afford a series of new compounds, 3,4-dihydro-4-amino-2-methoxy-2-methyl-2H-1-benzopyrans, in high yields, with good diastereoselectivity. BF3·OEt2 is also found to mediate this transformation under mild reaction conditions.