Synthesis of Functionalized 3‐(1H‐Isochromen)‐chromones via Ag₂O‐Catalyzed Cascade Cyclization Reaction of o‐Hydroxyarylenaminones with o‐Alkynylbenzaldehydes

Abstract

A silver-catalyzed protocol for the synthesis of 3-(1H-isochromen)-chromones is described. The method involves an initial 6-endo-dig cyclization of o-alkynylbenzaldehydes and domino CÀ H alkylation and chromone annulation of the ohydroxyarylenaminones, which enables the installation of 1H-isochromen and chromone in a single structure. This synthetic strategy is advantageous for the excellent regioselectivity, step economy, concise one-pot methodology, gram-scale synthesis, as well as high bond-forming efficiency.

An Oxidative [3+2+1] Cyclization of Enaminones and N‐Alkenyl‐2‐pyrrolidinone: Access to Polysubstituted 4‐Alkylated 1,4‐dihydropyridines

“…[11] To the best of our knowledge, the synthesis of 1,4-DHPs using terminal olefins as the C4 source has never been documented, although several examples using enaminones as starting materials to construct 1,4-DHPs with other C4 sources (such as aldehydes, [12a-c] alkylamines, [12d-e] and CO 2 [12f] ) have been reported (Scheme 1d). With our continued interest in enaminones chemistry, [13] herein we demonstrate for the first time an oxidative [3 + 2 + 1] cyclization of enaminones and N-alkenyl-2-pyrrolidinone to construct useful polysubstituted 4-alkylated 1,4-DHPs by the AgNO 3 /K 2 S 2 O 8 /dietyl phosphite promoted system (Scheme 1e). In this protocol, the new strategy for the construction of 1,4-DHPs by using terminal olefins as the C4 source is first achieved, while also enriching 1,1-difunctionalization of terminal olefins involving cyclization.…”

Synthesis of functionalized tetrahydrodibenzo[b,g][1,8]naphthyridin-1(2H)-ones through base-promoted annulation of quinoline-derived dipolarophiles and cyclic enaminones

“…Notably, the conventional applications of nitrogen-containing heterocycle scaffolds 8 in base-catalyzed or base-promoted cyclization are shining the spotlight on annulation to achieve highly functionalized nitrogen heterocycles. 9 Among these widely used N -sources, cyclic enaminones have exhibited enormous potential as powerful synthons for the assembly of various nitrogen-containing frameworks. 10 We envisioned that the complicated structural motifs might be concisely assembled through a base-promoted [3 + 3] annulation or related sequential reaction.…”

Silver‐catalyzed Cascade Bis‐heteroannulation Reaction of Enynones and o‐Hydroxyphenyl Enaminones: Access to Highly Functionalized 3‐Furylmethyl Chromones

“…Quite recently, we presented an efficient silver-catalyzed protocol to construct 3-(1H-isochromen)-chromones from readily available o-alkynyl benzaldehydes and o-hydroxyphenyl enaminones, which enables the installation of 1Hisochromen and chromone in a single structure (Scheme 1d). 22 However, 3-furyl chromones have never been synthesized. Thus, developing new methods featuring step efficiency is yet highly desirable for the synthesis of 3-furyl chromones.…”