Synthesis of Angular Polycyclic Aromatic Hydrocarbons Via Ti(IV)-Promoted Aldol-Type Condensation of Silyl Enol Ethers with 2-Arylacetaldehydes

A novel one-pot synthesis of angular polycyclic hydrocarbon ring systems is described. The method involves Ti(IV)-promoted aldol-type condensation of silyl enol ethers with 2-arylacetaldehydes with concurrent cyclization and double dehydration of the adducts. Dehydrogenation of the partially saturated polyarene products either catalytically over palladium or with quinone oxidants, such as DDQ, affords fully aromatic polycyclic hydrocarbons. Examples of the synthesis of various phenanthrene, chrysene, benz[a]anthracene, and benz[j]acephenanthrylene derivatives via this route are presented.