Copper(I)‐Catalyzed [3+2] Cycloaddition/Ring‐Opening Rearrangement/[4+2] Cycloaddition/Aromatization Cascade: An Unprecedented Chemo‐ and Stereoselective Three Component Coupling of Sulfonyl Azide, Alkyne and N‐Arylidenepyridin‐2‐ amine to Pyrido[1,2‐a]pyrimidin‐4‐imine

Abstract

A novel synthetic protocol for the onepot chemo-and stereoselective construction of diversely functionalized pyridoAcycloaddition/aromatization cascade of sulfonyl azides, alkynes and N-arylidenepyridin-2-amines under mild reaction conditions is reported. In addition, the catalytic activity of copper(I)-modified zeolite, a recyclable, heterogeneous catalyst is also investigated, which gives improved yield compared to its homogeneous equivalents.

Regio- and Diastereoselective Synthesis of Dihydropyridopyrimidines via Cascade Reactions of 2-Aminopyridines with Morita–Baylis–Hillman Bromides of Nitroalkenes

“…The diverse bioactivities displayed by pyridopyrimidines motivated synthetic organic and medicinal chemists to develop novel and convenient methods for their synthesis . These include reactions involving aminopyridines in formal aza-Diels–Alder reaction, intramolecular cyclization, cyclization with 1,3-bielectrophiles, , multicomponent reactions, cyclocondensation, and metal mediated sequence . Synthetic approaches not involving aminopyridines are also known in the literature .…”

Chemistry in Confinement: Copper and Palladium Catalyzed Ecofriendly Organic Transformations within Porous Frameworks

“…When a 1,3‐diazadiene skeleton, namely, N‐arylidenepyridin‐2‐amine was used, a facile [4+2] cycloaddition was observed with N‐sulfonylketenimine, generated in situ from the Cu(I)‐Y zeolite catalyzed [3+2] cycloaddition of sulfonyl azides and terminal alkynes . The cycloaddition proceeded with reversal of chemoselectivity involving addition across the C=C double bond of N‐sulfonylketenimine and subsequent aromatization leads to pyrido[1,2‐α]pyrimidin‐4‐imines (3) (Scheme ), in contrast to the work reported by Lu et.…”

Tf2O-Mediated Cyclization of α-Acyl-β-(2-aminopyridinyl)acrylamides: Access to N-Substituted 4H-Pyrido[1,2-a]pyrimidin-4-imines

“…Wu and co-workers synthesized a series of pyrido­[1,2- a ]­pyrimidin-4-imines via formal [3 + 3] cyclocondensation and investigated their structure–activity relationship as potent 5-HT 6 antagonists . Recently, Namitharan and co-workers reported the direct synthesis of N-substituted pyrido­[1,2- a ]­pyrimidin-4-imines for the first time (Scheme B) . Nevertheless, to match the increasing scientific and practical demand, the development of facile and efficient synthetic approaches to N-substituted 4 H -pyrido­[1,2- a ]­pyrimidin-4-imines is much more desired.…”