Asymmetric Synthesis of All-Carbon Benzylic Quaternary Stereocenters via Conjugate Addition to Alkylidene and Indenylidene Meldrum’s Acids
作者:Ashraf Wilsily、Eric Fillion
DOI:10.1021/jo901559d
日期:2009.11.20
aryl group consistently leading to high enantioselectivities. The nature of the organozinc reagent on the efficiency and selectivity of the conjugateaddition was also investigated. The solid-state conformation was determined for a number of alkylidene Meldrum’s acids and correlated with the observed enantioselectivity in relation to the arene pattern of substitution.
Upon Brønsted base organocatalysis, ketone‐derived alkylidene Meldrum's acids proved to be competent vinylogous platforms able to undergo a formal (4+2) cycloaddition reaction with dihydro‐2,3‐furandione, providing an unprecedented route to 3,6‐dihydropyran‐2‐ones as spiro[4.5]decane derivatives with up to 98 % ee thanks to the commercially available Takemoto catalyst. Preliminary investigation showed
Enantioselective Copper-Catalyzed Conjugate Addition of Dimethylzinc to 5-(1-Arylalkylidene) Meldrum’s Acids
作者:Eric Fillion、Ashraf Wilsily、Tiantong Lou
DOI:10.1055/s-0029-1216845
日期:2009.6
The asymmetric formation of all-carbon quaternary benzylic stereocenters containing a methyl substituent was realized by the enantioselective copper-catalyzed 1,4-addition of dimethylzinc to alkylidene Meldrum’s acids in the presence of a chiral phosphoramidite. Copper source and ligand optimization studies are presented, as well as the scope and limitations of dimethylzinc addition to various alkylidene