Green and Efficient Construction of Chromeno[3,4-c]pyrrole Core via Barton–Zard Reaction from 3-Nitro-2H-chromenes and Ethyl Isocyanoacetate

Abstract

A regioselective one-pot method for the synthesis of 1-ethyl 2,4-dihydrochromene[3,4-c]pyrroles in 63–94% yields from available 2-phenyl-, 2-trifluoro(trichloro)methyl- or 2-phenyl-2-(trifluoromethyl)-3-nitro-2H-chromenes and ethyl isocyanoacetate through the Barton–Zard reaction in ethanol at reflux for 0.5 h, using K2CO3 as a base, has been developed.

Tunable Zinc-Mediated Reductive Cyclization of Diastereomeric 3-Nitro-4-phenacyl-2-(trihalomethyl)chromanes to Fused Pyrroline N-Oxides, Pyrrolines, and Pyrrolidines

“…We previously reported on the diastereoselective synthesis of trans,cis- ( tc -isomers) and trans,trans-isomers ( tt -isomers) of 3-nitro-4-phenacyl-2-(trifluoro­(trichloro)­methyl)­chromanes 1 from 3-nitro-2-trifluoro­(trichloro)­methyl-2 H -chromenes and α-morpholinostyrene under kinetic or thermodynamic control conditions . In continuation of our research aimed at developing methods for the preparation of Δ 3 -annulated chromane derivatives, and taking into account the important role of fluorine- and chlorine-containing heterocycles, in this work we investigated the reductive cyclization of chromanes 1 using various Zn-based reductive systems as a possible method for the synthesis of individual diastereomers of trifluoro­(trichloro)­methyl-substituted fused pyrroline N -oxides, pyrrolines and pyrrolidines (Scheme b). Successful solution of this problem would make available a number of new 3,4-fused chromans with promising biological properties.…”

Recent Advances of Michael/hetero‐Michael Addition Reaction in the Synthesis of 3‐Nitro‐2H‐chromene Derivatives

“…In addition, the introduction of the nitro group at the C3 position in 2H-chromene moiety leads to many biologically active drugs due to the easy transformation of the -NO 2 group into several functional groups, [19][20][21][22] exhibiting different pharmaceutical properties such as anticancer, [23] antioxidant [24][25] antiinflammatory, [26] anti-proliferative [27] and antibacterial activities. [28][29] Some representative bioactive compounds and natural products derived from 2H-chromene derivatives were shown in Figure 1. Furthermore, the chromene cores find significant relevance in various fields including laser dyes, [30a] organic light emitting devices, [30b] optical brighteners, [30c] organic scintillators, [30d] triplet sensitizers, [30e-f] fluorescence probes ,[30g] etc.…”

“…In addition, the introduction of the nitro group at the C3 position in 2 H ‐chromene moiety leads to many biologically active drugs due to the easy transformation of the –NO 2 group into several functional groups, [19–22] exhibiting different pharmaceutical properties such as anticancer, [23] antioxidant [24–25] anti‐inflammatory, [26] anti‐proliferative [27] and antibacterial activities [28–29] . Some representative bioactive compounds and natural products derived from 2 H ‐chromene derivatives were shown in Figure 1.…”