Asymmetric Synthesis of All-Carbon Benzylic Quaternary Stereocenters via Cu-Catalyzed Conjugate Addition of Dialkylzinc Reagents to 5-(1-Arylalkylidene) Meldrum's Acids
摘要:
The asymmetric synthesis of all-carbon benzylic quaternary stereocenters has been successfully achieved through copper-catalyzed addition of dialkylzinc reagents to 5-(1-arylalkylidene) and 5-(dihydroindenylidene) Meldrum's acids in the presence of phosphoramidite ligand. The resulting benzyl-substituted Meldrum's acids and 1,1-disubstituted indanes were obtained in good yields and up to 99% ee. The significance of substituting the position para, meta, and ortho to the electrophilic benzylic center was highlighted. A benzyl Meldrum's acid product was further transformed to a 3,3-disubstituted 1-indanone and a beta,beta-disubstituted pentanoic acid.
Al and friends: Asymmetricconjugateaddition of Me3Al to β,β‐disubstituted α,β‐unsaturated ketones in the presence copper and L1 leads to a highly efficient construction of an all‐carbon‐substituted chiral quaternarycenter. This result is the first example of an asymmetricconjugateaddition of Me3Al to acyclic enones to give a chiral quaternary carbon center with excellent yield and enantioselectivity
Halomethyl-metal compounds. LXIII. Insertion of phenyl(bromodichloromethyl)mercury-derived dichlorocarbene into benzylic carbon-hydrogen bonds. Stereochemistry and mechanism