Chloride-incorporating cascade dearomatization of isoquinolines with chloroformate and DMAD achieving 100% atom economy

A multicomponent dearomatization of isoquinolines was achieved using chloroformate and dimethyl acetylenedicarboxylate (DMAD). Distinct from conventional direct additions, this protocol proceeds <i>via</i> a novel cascade involving [4+2] cycloaddition and ring-opening with chloride incorporation. This method features 100% atom economy and provides direct access to 1-functionalized 1,2-dihydroisoquinolines in moderate yields with high regioselectivity.