α‐Csp³‐H Methylenation of Diketones to Synthesize Methylene‐Bridged Bis‐1,3‐Dicarbonyl Compounds and Polysubstituted Pyridines Using the DMSO/Selectfluor System

Abstract

A direct α‐Csp3‐H methylenation of 1,3‐diketones to afford methylene‐bridged bis‐1,3‐dicarbonyl derivatives using dimethyl sulfoxide (DMSO) as a one‐carbon source was achieved in moderate to high yields in the presence of Selectfluor. The 1,3‐diketones can also be efficiently converted into Hantzsch‐type pyridines via one‐pot three‐component annulation reaction in the presence of DMSO and ammonium salt. The procedure avoids the use of transition metal catalysts and the reaction is efficient and operationally convenient.

Selectfluor‐promoted Synthesis of 2,4‐ and 2,6‐Diarylpyridines Through Annulation of Aromatic Ketones with an Ammonium Source in DMF

“…Based on the aforementioned experimental results, and literature reports,, two plausible reaction mechanisms have been proposed to explain pyridine formation (Scheme ). Initially homo‐condensation of 1 at 120 °C yields a chalcone analogue A , which can react with ammonium acetate to give imine intermediate B.…”

Recent Advances in the Application of Selectfluor as a “Fluorine‐free” Functional Reagent in Organic Synthesis

“…[27] Meanwhile, they also found that using this Selectfluor/DMSO system, the direct C(sp 3 )-H methylenation of 1,3-diketones could be achieved (Scheme 14b). [28] Very recently, the same group reported a novel and efficent strategy for the construction of 3-acylquinoline by using acetophenone, anthranil and DMSO as the strating materials through a Selectuor mediated three-component reaction (Scheme 14c). [29] It was noteworthy to mention that DMSO served as both a carbon and solvent source.…”

An efficient 3-acylquinoline synthesis from acetophenones and anthranilviaC(sp3)–H bond activation mediated by Selectfluor

“…56 The same group also reported the reaction anthranil is an isoxazole derivative which has been used for synthesis of a couple of heterocycles by cleavage of N-O bond. [57][58][59][60][61] Inspired by these excellent pioneering work, especially Tiwari's report that quinolines can be transformed from the reaction of in situ generated a,b- unsaturated ketones from acetophenones via one-carbon homologation by DMSO followed by the aza-Michael addition of anthranils and subsequent annulation, 62 we were encouraged to use Selectuor [63][64][65][66][67][68] as an alternative oxidant for the synthetic approach to 3-acylquinolines from commercially available acetophenones and anthranil. In this case, DMSO was applied as both carbon source and reaction medium.…”