Laser synthesis: a solvent-free approach for the preparation of phenylthiazolo[5,4-b]pyridine derivatives

Abstract

We describe here a rapid and straightforward solvent-free method to access phenylthiazolo[5,4-b]pyridines using a Nd-YAG laser NANO-NY81-10 (λ = 355 nm, 10 Hz pulse frequency; 8 ns pulse duration).

Green Synthesis of Aromatic Nitrogen-Containing Heterocycles by Catalytic and Non-Traditional Activation Methods

“…Moreover, the conditions are solvent-, metal-and base-free. Polyethylene glycol-based dicationic ionic liquid [232] has been applied in a green protocol to synthesize 3H-imidazo [4,5-b]pyridine. Fe(III)-based PEG 1000 dicationic imidazolium ionic liquid ([PEG 1000 mim 2 ][FeCl 4 ] 2 )/toluene biphasic system served as a medium and catalyst as well to promote the reaction effectively providing 78% yield (Scheme 30) [233].…”

Sabinene: A New Green Solvent Used in the Synthesis of Thiazolo[5,4-b]pyridines by Thermal or Microwave Activation

“…On the basis of the results obtained in a previous study [40] involving coupling between 3-amino-2-chloropyridine 2a and phenyl isothiocyanate 3a to obtain N-phenylthiazolo [5,4-b]pyridin-2-amine 4a, the synthesis was first carried out in various conventional solvents before being performed in green solvents. To investigate the ranges and limits, the temperature was maintained at a set point of 110 • C for an internal temperature of 100 • C in a sealed tube for each experiment by conventional heating using a stirring plate.…”

“…After the reaction, the mixture was filtered with ethyl acetate and the desired compound was synthesised in a 66% yield (Table 4, entry 5). Six new structures were synthesised and obtained in high yields and purity by thermal and microwave activation, the other four having already been obtained in a previous study [40]. Secondly, we investigated the use of other pyridines substituted with an alkyltype electron donor group.…”

“…They can also be synthesised in a single step from a chloronitropyridine and a suitably substituted thioamide or thiourea [39]. We chose to use the one-step method starting from a 3-amino-2-chloropyridine derivative and an isothiocyanate, a synthetic method already used when we investigated laser irradiation as a new activation method in organic synthesis [40]. This reaction was chosen because of the interest of this type of heterocycle, but also because while the reagents are soluble, the product precipitates out of the medium, making it easy to visualise its production.…”