Divergent asymmetric synthesis of heterohelicenes via sequential organocatalyzed Povarov reaction and aromatization

Incorporating main-group elements into the backbone of chiral carbohelicenes can significantly alter their electronic and optical properties, which renders the asymmetric synthesis of heterohelicenes an appealing research field. Herein, we present the divergent asymmetric synthesis of two distinct types of heterohelicenes from the same starting material by employing the key Povarov reaction with chiral phosphoric acid catalysts. Specifically, the one-pot asymmetric Povarov reaction/oxidative aromatization yielded the C1-ortho-phenol-substituted [5]/[6]pyridohelicenes, while subsequent Pd(II)/base-mediated furan formation resulted in the formation of longer [7]/[8]heterohelicenes bearing both furan and pyridine moieties. Fruitful derivatizations of the chiral helicenes, along with their promising photophysical and chiroptical properties, have underscored the value of this method.