NH₄OAc‐Promoted Cascade Approach towards Aberrant Synthesis of Chromene‐Fused Quinolinones

Abstract

A concise cascade strategy for the synthesis of 6H‐chromeno[4,3‐b]quinolin‐6‐ones was developed from 4‐hydroxycoumarins and arylhydrazine hydrochlorides in DMSO. The synthetic strategy relies on dual role of ammonium acetate in generating 4‐aminophenyl coumarin from arylhydrazine via aryl radical formation, and Csp2‐H formylation of coumarin using DMSO as a methine source. The strategy is scalable, and an array of arylhydrazine hydrochlorides delivered chromene‐fused quinolinones in good to excellent yields.

Redox‐Divergent Construction of (Dihydro)thiophenes with DMSO

“…DMSO is environmentally friendly aprotic polar solvent, which has been widely used as an oxidant for alcohols, [11] alkyl halides, [12] epoxides, [13] alkenes, [14] and alkynes. [15] Meanwhile, DMSO could also be employed as source of methyl, [16] methine, [17] methylene, [18] methylthio, [19] methylsulfinyl, [20] and oxygen. [21] However,there were rare reports that DMSO could be employed as sulfur donor in organic reactions.…”

Redox‐Divergent Construction of (Dihydro)thiophenes with DMSO

“…DMSO is environmentally friendly aprotic polar solvent, which has been widely used as an oxidant for alcohols, [11] alkyl halides, [12] epoxides, [13] alkenes, [14] and alkynes. [15] Meanwhile, DMSO could also be employed as source of methyl, [16] methine, [17] methylene, [18] methylthio, [19] methylsulfinyl, [20] and oxygen. [21] However,there were rare reports that DMSO could be employed as sulfur donor in organic reactions.…”

Recent Advances on Synthesis of Fused Chromeno‐Quinoline Heterocycles under Transition Metal‐Free Condition

“…An interesting synthetic protocol [43] to form a chromenefused quinoline scaffold has been developed by Sakhuja et al Control experiment also confirmed that the reaction proceeded through radical mechanism (Scheme 15). A broad range of substrate scope was studied under the optimized condition to deliver moderate to good yields of the products.…”

“…A fused tetracyclic chromeno[2,3-b]quinoline scaffold was synthesized via a two-step synthetic methodology [48] Another multi-step synthetic methodology [49] for the synthesis of 7-(trifluoromethyl)-6H-chromeno [4,3-b]quinolin-6-one derivatives 44 was developed by Iaroshenko et al under transition metal-free conditions. In the first step 4-chloro-3-(trifluoroacetyl)coumarin (43) was derived through the intermediates 41 and 42. In the second step, 4-chloro-3-(trifluoroacetyl)coumarin was reacted with substituted anilines followed by treatment with concentrated H 2 SO 4 to obtain the desired tetracyclic chromeno-quinolines (Scheme 26).…”