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Highly cis-selective Rh(I)-catalyzed cyclopropanation reactions.

The Journal of organic chemistry (2011-03-19)
Marianne Lenes Rosenberg, Klára Vlašaná, Nalinava Sen Gupta, David Wragg, Mats Tilset
ABSTRACT

The performance of recently reported highly cis-diastereoselective Rh(I) cyclopropanation catalysts has been significantly improved by a systematic study of different reaction parameters (catalyst activation, solvent, temperature, stoichiometry). The catalyst efficiency and diastereoselectivity were enhanced by changing the activating agent from AgOTf to NaBArf. With this new system, the Rh(I) catalyst was shown to be a highly efficient and cis-diastereoselective cyclopropanation catalyst in reactions between α-diazoacetates and a range of different alkenes and substituted derivatives. Particularly noteworthy is the remarkable reactivity and cis-diastereoselectivity displayed in the reactions between ethyl diazoacetate and cyclopentene, 2,5-dihydrofuran, and benzofuran, with yields up to 99% and cis-selectivities greater than 99%.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Ethyl diazoacetate, contains ≥13 wt. % dichloromethane