Asymmetric Fluorination of α-Branched Cyclohexanones Enabled by a Combination of Chiral Anion Phase-Transfer Catalysis and Enamine Catalysis using Protected Amino Acids
作者:Xiaoyu Yang、Robert J. Phipps、F. Dean Toste
DOI:10.1021/ja500882x
日期:2014.4.9
cycles operating together in a matched sense, high enantioselectivites can be achieved, and we envisage that this dual catalysis method has the potential to be more broadly applicable, given the breadth of enaminecatalysis. It also represents a rare example of chiral enaminecatalysis operating successfully on α-branched ketones, substrates commonly inert to this activation mode.
A p-toluenesulfonic acid catalyzed fluorination of α-branched ketones for the construction of fluorinated quaternary carbon centers has been developed, featuring a broad substrate scope, environmentally benign reaction conditions, and operational simplicity.
Abstract A practical synthesis of propargylic alcohols was developed by alkynylation of aldehydes mediated by zinc and allylbromide. Aromatic, aliphatic and vinyl aldehydes react with phenylacetylene or 1-hexyne to obtain various propargylic alcohols at room temperature in up to 98% yield. This method is characterized with inexpensive materials, wide substrate scope, and mild reaction conditions,