Unconventional [2 + 3] Cyclization Involving [1,4]-Sulfonyl Transfer to Construct Polysubstituted Fluorazones as Inhibitors of Indoleamine 2,3-Dioxygenase 1

Abstract

An unconventional [2 + 3] cyclization of pyridinium ylides with 2-ylideneoxindoles has been developed for the facile construction of pharmacologically interesting polysubstituted 9H-pyrrolo­[1,2-a]­indol-9-ones (fluorazones). Mechanistic studies revealed that the reaction, which has a broad substrate scope, proceeds via intermolecular [1,4]-sulfonyl transfer. Moreover, biological evaluation showed that polysubstituted fluorazone 3ak potently inhibits indoleamine 2,3-dioxygenase 1, kynurenine production, and immunotolerance in tumors.

Gold‐Catalyzed Synthesis of Ortho‐Quinone Methide Analogues as Reactive Synthetic Precursors

“…The carbonyl and exomethylene units of 2‐alkenyl indolin‐3‐ones are structurally similar to those of ortho ‐quinone methide ( o ‐QM, Figure 1a, center) [3] . 2‐Alkenyl indolin‐3‐ones have been reported as important synthetic intermediates in [4+2] cycloadditions with electron‐rich dienophiles, conjugate additions with nucleophiles, cyclopropanations, and other transformation reactions [1b,4–7] . Furthermore, 2‐exomethylene indolin‐3‐ones (Figure 1a, right) can be applied to the development of various bioactive and functional materials because of their fundamental or related structures [8–16] .…”

Chemo- and Diastereoselective Cycloisomerization/[2 + 3] Cycloaddition of Enynamides: Synthesis of Spiropyrazolines as Potential Anticancer Reagents

“…Despite the significant efforts devoted to the synthetic and biological study of pyrazole and fused pyrazole compounds, the spiropyrazoline scaffold has been much less explored . Therefore, based on our continued interest in developing synthetic strategies for medicinally relevant scaffolds, we believe that developing new synthetic approaches to construct novel spiropyrazoline scaffolds will provide valuable opportunities for drug discovery.…”

DABSO as a SO2 gas surrogate in the synthesis of organic structures

“…[5][6][7][8][9][10][11] There is a surge of attention paid to innovative and improved synthetic techniques for introduction of sulfur including functional groups, like sulfones and sulfonamides, in the structure of agrochemicals, medicines, and other organic materials. [12][13][14][15][16][17][18] Thus, the development of convenient and stable SO 2 surrogates is thought to be a key driver in the revitalization of sulfur-based organic synthesis research. Hence, 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide), abbreviated as DABSO, has been manufactured 19 to use it as a reagent for sulfonating organic structures.…”