Lewis acid-induced reaction of homophthalic anhydride with imines: a convenient synthesis of trans-isoquinolonic acids

Cycloaddition of imines with homophthalic anhydride in the presence of BF 3 leads to the trans isomers of isoquinolonic acids with a high stereoselectivity and avoids the formation of homophtalic amides. This catalyst extends the scope of the reaction to imines which did not react under previously described conditions.