A Direct Synthesis of Isocytosine Analogues by Carbonylative Coupling of α-Chloro Ketones and Guanidines

Modular access to sulfur substituted analogues of isocytosine via photoredox catalysis

A photoredox approach for synthesizing sulfur-substituted analogues of isocytosine via coupling of modular phenyl propargyl chloride with thiourea has been reported. The resulting product with an amine group was found amenable to various late-stage modifications, providing access to a broad range of sulfur-containing isocytosine derivatives.

N-, O- and S-Heterocycles Synthesis in Deep Eutectic Solvents

The synthesis of heterocycles is a fundamental area of organic chemistry that offers enormous potential for the discovery of new products with important applications in our daily life such as pharmaceuticals, agrochemicals, flavors, dyes, and, more generally, engineered materials with innovative properties. As heterocyclic compounds find application across multiple industries and are prepared in very large quantities, the development of sustainable approaches for their synthesis has become a crucial objective for contemporary green chemistry committed to reducing the environmental impact of chemical processes. In this context, the present review focuses on the recent methodologies aimed at preparing N-, O- and S-heterocyclic compounds in Deep Eutectic Solvents, a new class of ionic solvents that are non-volatile, non-toxic, easy to prepare, easy to recycle, and can be obtained from renewable sources. Emphasis has been placed on those processes that prioritize the recycling of catalyst and solvent, as they offer the dual benefit of promoting synthetic efficiency while demonstrating environmental responsibility.

3-Cyclohexyl-6-phenyl-1-(p-tolyl)pyrimidine-2,4(1H,3H)-dione

The synthesis of a novel uracil derivative, 3-cyclohexyl-6-phenyl-1-(p-tolyl)pyrimidine-2,4(1H,3H)-dione (4), is reported via a four-component reaction involving an α-chloroketone (1), an aliphatic isocyanate (2), a primary aromatic amine (3) and carbon monoxide. The proposed reaction mechanism involves a Pd-catalyzed carbonylation of 2-chloro-1-phenylethan-1-one (1), leading to a β-ketoacylpalladium key intermediate, and, at the same time, in situ formation of non-symmetrical urea deriving from cyclohexyl isocyanate (2) and p-toluidine (3). After a chemo-selective acylation of the non-symmetrical urea and the subsequent cyclization of the acylated intermediate, 3-cyclohexyl-6-phenyl-1-(p-tolyl)pyrimidine-2,4(1H,3H)-dione (4) is formed. Uracil derivative 4 was isolated in good yield (73%) and fully characterized by 1H, 13C, 2D 1H-13C HSQC and 2D 1H-13C HMBC NMR, FT-IR spectroscopy and GC-MS spectrometry.

Pd-Catalyzed Ring-Opening/Arylation/Cyclization of 2-Aminothiazole Derivatives Provides Modular Access to Isocytosine Analogues

We report a Pd-catalyzed ring-opening/arylation/cyclization reaction sequence between 2-aminothiazoles and aryl (pseudo)halides that provides modular access to isocytosine analogues. The scope of the reaction is broad with respect to both coupling partners and a robustness test demonstrated the functional group tolerance of the methodology. Visual kinetic analysis revealed that the product may inhibit catalyst turnover for some substrates.

Palladium-catalyzed cascade carbonylative annulation between alkene-tethered aryl iodides and carbon monoxide

Rapid construction of molecules bearing all-substituted quaternary stereocenters represents a highly significant but challenging task in organic synthesis. Herein, we report a novel palladium-catalyzed cascade between alkene-tethered aryl iodides and carbon monoxide, which has resulted in a practical and powerful method for the synthesis of complex polycyclic molecules containing aryl-substituted quaternary stereocenters. Mechanistic studies suggested that the reaction proceeded via a Heck-type carbonylative cyclization, followed by a ketene-involved Friedel-Crafts acylation.

Towards a sustainable synthesis of amides: chemoselective palladium-catalysed aminocarbonylation of aryl iodides in deep eutectic solvents

A Pd-catalysed aminocarbonylation of aryl iodides has been first achieved in environmentally responsible and recyclable deep eutectic solvents.