An efficient Fe(OTf)3-catalyzed nucleophilicsubstitution of cyclic or acyclic tertiary alcohols with difluoroenoxysilanes is developed, which provides a facile protocol for assembling structurally diverse α,α-gem-difluoroketones featuring a quaternary carbon center in good to excellent yields under mild conditions. Moreover, the diverse product elaborations highlight the utility of this protocol,
the synthesis of fluorinatedcompounds have been intensively studied, recently. Development of practical fluorinating reagents is indispensable for this purpose. Herein, bench-stable electrophilic fluorinating reagents were synthesized as N-fluorobenzenesulfonimide (NFSI) substitutes. Reagents obtained by replacing one of the NFSI sulfonyl groups with an acyl group led to the highly selective monofluorination
A highly efficient metal-free aldol-type reaction of various acetals or ketals with fluorinated silylenolethers catalysed by less than 1 mol% HClO4 (70 wt%, aq.) is developed. This provides expedient access to a wide array of valuable fluoroalkyl ethers featuring a ketone carbonyl functionality in good to excellent yields (40 examples). Furthermore, the thus obtained adducts are readily elaborated
Organocatalyzed Enantioselective Protonation of Silyl Enol Ethers: Scope, Limitations, and Application to the Preparation of Enantioenriched Homoisoflavones
In the present work, enantioselective protonation of silylenolethers is reported by means of a variety of chiral nitrogen bases as catalysts, mainly derived from cinchonaalkaloids, in the presence of various protic nucleophiles as proton source. A detailed study of the most relevant reaction parameters is disclosed allowing high enantioselectivities of up to 92% ee with excellent yields to be achieved
TiCl4-Promoted Mukaiyama Aldol Reaction of Fluorinated Silyl Enolates for the Construction of a Quaternary Carbon Center
作者:Yong Guo、Wengui Wang、Qing-Yun Chen
DOI:10.1055/s-0031-1289535
日期:2011.11
A method for the preparation of α-fluoro-β-hydroxyphenones from Mukaiyama aldol reactions of various aldehydes and fluorinated silyl enolates was reported. The reaction was promoted by TiCl4 and afforded the desired products in good to excellent yields. The relative stereochemistry of the products was determined by X-ray analysis of single crystals of syn-2-fluoro-3-hydroxy-2-methyl-1,3-diphenylpropan-1-one and anti-2-fluoro-3-hydroxy-2,4,4-trimethyl-1-phenylpentan-1-one.