Substrate‐Controlled Aza‐Ene/Prins Cyclization for the Synthesis of Dihydroquinoline and Oxocene Derivatives

Abstract

A substituent controlled aza‐ene/Prins cyclization strategy has been developed for the one‐pot synthesis of dihydroquinoline tethered tetrahydropyran derivatives from ortho‐aminoaryl alkenols and aromatic aldehydes using 30 mol% TMSOTf at 60 °C. The reaction proceeds through a sequential aza‐ene and Prins cyclization. In the case of nitro and cyano substituted aromatic aldehydes, eight‐membered oxocene derivatives were obtained under similar conditions. This is the first report on the introduction of tetrahydropyran ring at 4th position of dihydroquinoline from ortho‐aminoaryl alkenol and aromatic aldehyde in the presence of an acid catalyst. A catalytic amount of TMSOTf facilitates aza‐ene and Prins cyclizations sequentially in a single‐step.

Eight-Membered Rings With One Oxygen Atom

“…184 Few examples of benzoxocenes 257 are obtained from aza-ene/Prins cyclization reaction of O-aminoaryl alkenols 256 with electron-deficient aryl aldehydes promoted by TMSOTf in DCE (Scheme 41). 185 Scheme 39…”