One-pot synthesis of imidazo[1,2-a]pyridines from benzyl halides or benzyl tosylates, 2-aminopyridines and isocyanides

Gold‐Catalyzed Redox Synthesis of Imidazo[1,2‐a]pyridines using Pyridine N‐Oxide and Alkynes

“…[9] The imidazo[1,2- a ]pyridine ring system can be formed in many ways: typically they are formed via condensation of aminopyridines and α-haloketones [10] and can be formed by a one-pot condensation of an aldehydes, isonitrile and a 2-aminopyridine though this approach can require harsh conditions so limiting the scope of functionalities tolerated in this reaction. [11] More recently a number of copper catalysed methodologies have been developed, namely a three-component reaction of a 2-aminopyridine with an aldehyde and an alkyne, [12] a dehydrogenative coupling of a ketone with a 2-aminopyridine conducted at 40°C, [13] an oxidative cyclization of a halo-alkyne with an amino-pyridine at 60°C, [14] and an oxidative reaction between a ketone and a 2-aminopyridine carried out at 120°C. [15] Two further methods reported recently are worthy of note, the iron(III)-catalysed reaction between a nitro-olefin and an amino-pyridine achieved at 80°C, [16] and the silver-mediated oxidative coupling between terminal alkynes and a 2-aminopyridine conducted at 110°C.…”

Recent synthetic scenario on imidazo[1,2-a]pyridines chemical intermediate

“…These aldehydes then underwent a MCR with 2-aminopyridines and isocyanides to afford imidazo[1,2-a]pyridines 1.92a-b (Scheme 21) [58,59]. In addition, they further developed a one-pot synthesis of imidazo[1,2-a]pyridines 1.97b through multicomponent couplings of 2-aminopyridines, aldehydes and arylalkynecarboxylic acids 1.96b, which were generated in situ through palladium-catalyzed coupling of aryl iodides and propiolic acid (Scheme 25) [65].…”

One‐pot Three‐component Synthesis of Furan‐based Heterocycles from Benzyl Halides

“…Then, they undergo a three‐component reaction with α‐hydroxy C─H acids and tert ‐butyl isocyanide without adding any catalyst. Although DMSO‐potassium carbonate (K 2 CO 3 ) is a familiar oxidizing agent for the synthesis of many heterocyclic compounds such as benzothiazoles , quinazolinones , oxadiazoles , and imidazo[1,2‐ a ]pyridines , the broad scope and synthetic application of this reagent for the construction of furan analogs in MCR have not been reported. This protocol constructed the well‐known reaction but is not restricted to aldehyde substrate.…”