Recent Advances in the Green Synthesis of Heterocycles: From Building Blocks to Biologically Active Compounds

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

Recent advances in the environmentally benign synthesis of aromatic N-heterocycles are reviewed, focusing primarily on the application of catalytic methods and non-traditional activation. This account features two main parts: the preparation of single ring N-heterocycles, and their condensed analogs. Both groups include compounds with one, two and more N-atoms. Due to the large number of protocols, this account focuses on providing representative examples to feature the available methods.

Rh-Catalyzed Environmentally Benign Selective Hydrogenation of a Broad Variety of Functional Groups Using Al-Water as a Hydrogen Source

Supported rhodium catalysts were screened to catalyze the one-step hydrogenation of a broad variety of functional groups. The results show that 5% Rh/Al2O3 and 5% Rh/C performed well in controlling selective hydrogenation under the desired amount of time and temperature. In this regard, partial and full hydrogenation were achieved by controlling reaction time or temperature. In addition to aliphatic C–C, C–N, C–O, and N–O multiple bonds, the applicability of this method was demonstrated by the hydrogenation of C=C double bonds of arenes, which is considered challenging. Importantly, the Al-H2O system producing hydrogen in situ and the high, controllable selectivity make this protocol environmentally benign and highly efficient.

Recent Advances in the Synthesis of Isoquinoline-Fused Benzimidazoles

This review includes recent developments in the synthesis of benzo[4,5]imidazo[2,1-a]isoquinolines with particular attention given to categorizing protocols based on the structural features of the ring architecture and crystallographically characterized reaction products.

Preparation of Deuterium Labeled Compounds by Pd/C-Al-D2O Facilitated Selective H-D Exchange Reactions

The chemo/regioselective H-D exchange of amino acids and synthetic building blocks by an environmentally benign Pd/C-Al-D₂O catalytic system is described. Due to the importance of isotope labeled compounds in medicinal chemistry and structural biology, notably their use as improved drug candidates and biological probes, the efficient and selective deuteration methods are of great interest. The approach is based on selective H-D exchange reactions where the deuterium source is simple D₂O. D₂ gas is generated in situ from the reaction of aluminum and D₂O, while the commercially available palladium catalyst assists the H-D exchange reaction. The high selectivity and efficiency, as well as the simplicity and safe nature of the procedure make this method an environmentally benign alternative to current alternatives.