Triflimide: An Overlooked High-Performance Catalyst of the Mukaiyama Aldol Reaction of Silyl Ketene Acetals with Ketones
作者:Han Yong Bae、Benjamin List
DOI:10.1002/chem.201803142
日期:2018.9.18
The Mukaiyamaaldolreaction is a widely applied carbon–carbon bond forming reaction. However, despite numerous well‐established methods using aldehydes as acceptors, only few examples exist with ketones. Here we report a highly practical catalytic approach to this transformation, namely, the triflimide catalyzedMukaiyamaaldolreaction of silyl ketene acetals with ketones. This method exhibits a
A Reformatsky-type reaction has been developed using iron catalysis in acetonitrile or DMF. Reduction of iron(II) bromide by manganese metal in acetonitrile provides a low-valent iron catalyst, which is the active species; under these conditions, α-chloroesters or nitriles can both be converted into their corresponding derivatives. The method was applicable to both ketones and aldehydes, resulting in the formation of β-hydroxyesters under mild conditions.
Coupling reactions of α-chloroesters with aryl halides (α-arylation) or carbonyl compounds (Reformatsky) using nickel catalyst allow, under mild conditions, the preparation of various functionalized aryl propionic acid derivatives or β-hydroxyesters. In the synthesis of aryl propionic acid derivatives, the process is efficient with aryl halides bearing either electron-withdrawing or electron-donating
Copper‐Catalyzed Enantioselective Reductive Aldol Reaction of α,β‐Unsaturated Carboxylic Acids to Alkyl Aryl Ketones: Silanes as Activator and Transient Protecting Group
The first reductivealdolreaction of α,β-unsaturated carboxylic acids was developed in the presence of copper/bisphosphine catalysts. The reaction demonstrated the usability of in situ protection of α,β-unsaturated carboxylic acids by a hydrosilane for the reductive C−C bond formation. The Si−O bond in the aldol products is readily cleaved by a standard workup, showing the silane worked as not only
Copper hydride‐catalyzedconjugate reduction‐intermolecular aldol addition domino reactions were realized using α,β‐unsaturated carboxylates as hydride acceptors and a silane as the reducing reagent. High diastereoselectivities were achieved with 4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene as the ligand and tert‐butyl acrylate as the hydride acceptor.