Organocatalyzed Domino [3+2] Cycloaddition/Payne-Type Rearrangement using Carbon Dioxide and Epoxy Alcohols.

An unprecedented organocatalytic approach towards highly substituted cyclic carbonates from tri- and tetrasubstituted oxiranes and carbon dioxide has been developed. The protocol involves the use of a simple and cheap superbase under mild, additive- and metal-free conditions towards the initial formation of a less substituted carbonate product that equilibrates to a tri- or even tetrasubstituted cyclic carbonate under thermodynamic control. The latter are conveniently trapped in situ, providing overall a new domino process for synthetically elusive heterocyclic scaffolds.

Highly Efficient Organocatalyzed Conversion of Oxiranes and CO2 into Organic Carbonates.

Invited for the cover of this issue is the group of Arjan Kleij at the Institute of Chemical Research of Catalonia (ICIQ). The image shows how naturally occurring compounds such as tannic acid can be used to devise highly efficient CO2 conversion catalysis. The Full Paper itself is available at 10.

Highly Efficient Organocatalyzed Conversion of Oxiranes and CO2 into Organic Carbonates.

A binary catalyst system based on tannic acid/NBu4X (X=Br, I) is presented as a highly efficient organocatalyst at very low catalyst loading for the coupling of carbon dioxide and functional oxiranes to afford organic carbonates in good yields. The presence of multiple polyphenol fragments within the tannic acid structure is considered to be beneficial for synergistic effects that lead to higher stabilization of the catalyst structure during catalysis. The observed turnover frequencies (TOFs) exceed 200 h(-1) and are among the highest reported to date for organocatalysts in this area of CO2 conversion.