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The role of carbodiimide as dehydrant in the chemo-, regio- and stereoselective Pd (II/0)-catalyzed hydrocarboxylation of various alkynes with HCOOH releasing CO in situis reported for the first time to obtain α,β-unsaturated carboxylic acids. Both symmetrical and unsymmetrical monoalkynes show good reactivity. Importantly, 2,2'-(1,4-phenylene)diacrylic acid can also be synthesized in high yield through the dihydrocarboxylation of 1,4-diethynylbenzene. Besides, an excellent result in gram scale experiment and TON up to 900 can be obtained, displaying the efficiency of this protocol. Notably, regulating the types and concentrations of dehydrant can control the CO generation, avoiding directly operating toxic CO and circumventing sensitivity issue to the CO amount. On the basis of the attractive features of formic acid including easy preparation through CO2hydrogenation and efficient liberation of CO, this protocol using formic acid as bridging reagent between CO2and CO can be perceived as an indirect utilization of CO2, offering an alternative method for preparing acrylic acid analogues.

Compounds bearing organophosphorus motifs and 2-oxazolidinone have found numerous applications in pharmaceutical chemistry, homogeneous catalysis, and organic materials. Here, we describe an efficient and selective protocol for straightforward access to a series of 5-((diarylphosphoryl)methyl)oxazolidin-2-ones via the copper-catalyzed difunctionalization of the C≡C bond of propargylic amines with CO2and phosphine oxide. Notably, copper catalysis is a sustainable and benign catalytic mode. This reaction proceeds under mild reaction conditions, which is operationally simple and scalable with a broad scope, exclusive selectivity, and good functional group compatibility. Mechanistic studies suggest a one-pot tandem cyclization/radical addition sequence, along with the phosphorylation/cyclization scheme.

A cobalt-bicyclic guanidine catalytic system consisting of CoBr2and TBD for the carboxylative cyclization of terminal propargylic amines with CO2was firstly developed to produce 2-oxazolinones efficiently.

Inexpensive and efficient Cu(I) catalysis is reported for the synthesis of α-hydroxy ketones from propargylic alcohols, CO2, and water via tandem carboxylative cyclization and nucleophilic addition reaction. Notably, hydration of propargylic alcohols can be carried out smoothly under atmospheric CO2pressure, generating a series of α-hydroxy ketones efficiently and selectively. This strategy shows great potential for the preparation of valuable α-hydroxy ketones by using CO2as a crucial cocatalyst under mild conditions.