Quinoline-Fused Lactones via Tandem Oxidation Cyclization: Metal-Free sp³ C–H Functionalization

Abstract

A unique lactonization of 2-methyl-3-acyl-4-phenylquinolines using PhIO as the oxidant and selectfluor as an additive is reported. The reaction occurs under ambient conditions through tandem oxidation and cyclization of sp 3 C−H bonds under metal-free conditions. The heterocycle-fused lactones are obtained in moderate to good yield.

Metal‐Free Synthesis of Anthranils by PhIO Mediated Heterocyclization of ortho‐Carbonyl Anilines

“…Most of these methods suffer from use of strong acid/base, transition metal, high temperature, pre‐functionalized substrates and generate toxic by‐products such as tin. In continuation of our research on PhIO mediated heterocycle synthesis [11a–b] …”

Recent Advances in the Synthesis of Fused‐Cyclic Quinolines

“…Cyclization reaction of 2-methyl-3-acyl-4-phenylquinolines 150 using PhIO as the oxidant and selectfluor as an additive let to quinoline-fused lactones 151 (Scheme 48). [119] As shown in Scheme 49, quinoline-fused lactone derivatives 154 were produced through oxidative (4 + 2)-cyclization/ aromatization/lactonization tandem reaction of N-aryl glycine esters 152 with propargyl alcohols 148 in presence of FeCl 3 , TFA, O 2 atmosphere and MeCN. [120] Mechanistically, iron(III) oxidation of intermediate A, which is constructed through intermolecular transesterification of the glycine ester 152 with propargyl alcohol 153, gives intermediate B. in addition to iron(III) as oxidant agent, presence of air atmosphere is essential for reaction progress, so that, according to the optimization table the reaction in argon atmosphere failed to give any conversion.…”

“…Cyclization reaction of 2‐methyl‐3‐acyl‐4‐phenylquinolines 150 using PhIO as the oxidant and selectfluor as an additive let to quinoline‐fused lactones 151 (Scheme 48). [119] …”

Deoxygenation of N‐heterocyclic N‐oxides with Selectfluor and disulfane

“…It is well known that Selectfluor is both a robust and effective oxidant and an electrophilic fluorinating reagent [15]. By using this metal-free reagent a great number of synthetic approaches including crosscouplings [16], site-selective sp 3 C-H functionalizations [17], oxidative halogenations [15], DielsÀAlder cycloadditions [18], and other organic applications [19] were performed with quantitative yields.…”