Abstract
An efficient and “green” protocol for the synthesis of 3-acylimidazo[1,2-a]pyridines through intramolecular oxidative α-amination of carbonyl compounds has been developed. The reaction proceeds smoothly utilizing I2 as a catalyst and H2O2 as an oxidant under neat condition with broad substrate scope. Several complex nitrogen-containing fused rings are conveniently constructed, which are not easy to access by traditional methods.
Highlights
An efficient and “green” protocol for the synthesis of 3-acylimidazo[1,2-a]pyridines through intramolecular oxidative a-amination of carbonyl compounds has been developed
Paper be solved in the traditional synthetic methods such as the use of complex starting materials, metal vestigial, narrow substrate scopes and harsh conditions
The substrates bearing various substituents at the carbonyl terminal position were subsequently evaluated (Table 3). Groups such as electron-rich methyl, electron-withdrawing uoro, chloro, bromo substituents on the arene ring were tolerant well and afforded the desired products in similar yields (2j–2n), suggesting that electronic effect exerted by the substituents at the terminal of the carbonyl component had almost no effect on this reaction
Summary
I2-catalyzed intramolecular oxidative amination of C(sp3)–H bond: efficient access to 3-acylimidazo [1,2-a]pyridines under neat condition†. An efficient and “green” protocol for the synthesis of 3-acylimidazo[1,2-a]pyridines through intramolecular oxidative a-amination of carbonyl compounds has been developed. Intramolecular C–H bond activation to build C–X (N/O) bonds is of great signi cance in the construction of heterocyclic scaffolds, which could afford wide application for the direct synthesis of biologically active molecules and drug candidates.[1] In contrast to unsaturated C–H bond activation reactions, transformations of Csp3–H bond to Csp3–X bonds are still limited.[2] Over the past decades, several groups have developed transition-metal-catalysed intramolecular aliphatic C–H aminations and oxygenations, affording an atom-economic and efficient access to a series of N/O-containing heterocyclic compounds.[3] most of these methods face the limitations of transition metal residuals, expensive ligands, harsh conditions and narrow substrate scope. We develop a convenient, efficient and “green” approach for the construction of 3-acylimidazo[1,2-a]pyridines through intramolecular oxidative a-amination of carbonyl compounds, which utilizing I2 as a catalyst and H2O2 as the only oxidant. Replacing the catalyst I2 with other iodides such as TBAI, NaI did not improve the
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