Sequence-controlled polymers, including biopolymers such as DNA, RNA, and proteins, have attracted much attention recently because of their sequence-dependent functionalities. The development of an efficient synthetic approach for non-natural sequence-controlled polymers is hence of great importance. Multicomponent polymerizations (MCPs) as a powerful and popular synthetic approach for functional polymers with great structural diversity have been demonstrated to be a promising tool for the synthesis of sequence-controlled polymers. In this work, we developed a facile metal-free one-pot multicomponent tandem polymerization (MCTP) of activated internal alkynes, aromatic diamines, and formaldehyde to successfully synthesize structural-regulated and sequence-controlled polyheterocycles with high molecular weights (up to 69 800 g/mol) in high yields (up to 99%). Through such MCTP, polymers with the in situ generated multisubstituted tetrahydropyrimidines or dihydropyrrolones in the backbone and inherent luminescence can be easily obtained with high atom economy and environmental benefit, which is inaccessible by other synthetic approaches.

Dirhodium tetracarboxylates are versatile catalysts for the reactions of donor/acceptor carbenes. They catalyze a variety of transformations, including enantioselective intermolecular cyclopropanations. This study is focused on understanding the kinetics of the rhodium-catalyzed cyclopropanation, and this information was used to develop conditions for conducting the reactions with very low catalyst loadings. The enantioselective cyclopropanation of styrenes can be conducted with a catalyst loading of 0.001 mol % and still maintain high levels of enantioselectivity (86−99% ee). A triarylcyclopropanecarboxylate (TPCP) catalyst, Rh 2 (p-Ph-TPCP) 4 , was the optimum catalyst for maintaining high enantioselectivity with very low catalyst loading. The reaction also benefited from using dimethyl carbonate as the solvent, an environmentally benign and nontoxic material.

The dirhodium tetracarboxylate-catalysed asymmetric cyclopropanation has been applied to the enantioselective syntheses of pharmaceutically relevant 1-aryl-2-heteroaryl- and 1,2-diheteroarylcyclopropane-1-carboxylates.

A mild method for accessing diazo compounds via aerobic oxidation of hydrazones is described. This catalytic transformation employs a Cu­(OAc)2/pyridine catalyst and molecular oxygen from ambient air as the terminal oxidant, generating water as the sole byproduct and affording the desired diazo compounds within minutes at room temperature. A broad array of electronically diverse aryldiazo esters, ketones, and amides can be accessed. Pyridine dramatically enhances the rate of the reaction by solubilizing the copper catalyst and serving as the Brønsted base in the turnover-limiting proton-coupled oxidation of hydrazone by copper­(II). Insights gained from mechanistic studies led to expansion of the scope of this method to include diaryl hydrazones, delivering diaryl diazomethane derivatives, which cannot be accessed via established diazo transfer methods. The products of this method may be employed in rhodium carbene catalysis without isolation of the diazo intermediate to afford cyclopropane products in good yield with high enantioselectivity.

No abstract