Synthesis of α-Halo-α,α-difluoromethyl Ketones by a Trifluoroacetate Release/Halogenation Protocol
摘要:
Three series of alpha-halo-alpha,alpha-difluoromethyl ketones are prepared from highly alpha-fluorinated gem-dials by exploiting the facile release of trifluoroacetate, followed by immediate trapping of the liberated alpha,alpha-difluoroenolate with an electrophilic chlorine, bromine, or iodine source. The products are typically isolated in good yields, even in the case of sensitive, alpha-iodo-alpha,alpha-difluoromethyl ketones. Also, we demonstrate that an alpha-iodo-alpha,alpha-difluoromethyl ketone will participate in a copper-promoted reaction to forge a new carbon-carbon bond.
Generation of Magnesium Pentafluoropropen-2-olate from Hexafluoroisopropanol and Synthesis of 2,2,4,4,4-Pentafluoro-3,3-dihydroxyketones
摘要:
2,2,4,4,4-Pentafluoro-3,3-dihydroxyketones are valuable precursors to difluoroenolates following fragmentation during the release of trifluoroacetate; however, there are few synthetic strategies to prepare this unique class of compound. We addressed this issue and report a mild, two-step synthesis of 2,2,4,4,4-pentafluoro-3,3-dihydroxyketones from aldehydes. Specifically, aldehydes are treated with pentafluoropropen-2-olate, generated from a new fragmentation of hexafluoroisopropanol with a mixed Mg/Li amide, to give pentafluoroalcohols. A subsequent oxidation with Dess-Martin periodinane provides the targets in good isolated yields.
Conversion of methyl ketones and methyl sulfones into α-deutero-α,α-difluoromethyl ketones and α-deutero-α,α-difluoromethyl sulfones in three synthetic steps
作者:Munia F. Sowaileh、Changho Han、Robert A. Hazlitt、Eun Hoo Kim、Jinu P. John、David A. Colby
DOI:10.1016/j.tetlet.2016.12.018
日期:2017.2
Deuterodifluoromethyl ketones and sulfones were assembled in three synthetic steps from methylketones and sulfones, respectively. The key synthetic transformation is the deuteration of the difluorocarbanion generated by the release of trifluoroacetate from highly α-fluorinated gem-diols. High levels of deuterium on the "CF2D" group were routinely observed. This strategy is mild and versatile and it
Magnesium-Promoted Additions of Difluoroenolates to Unactivated Imines
作者:Alex L. Nguyen、Hari R. Khatri、James R. Woods、Cassidy S. Baldwin、Frank R. Fronczek、David A. Colby
DOI:10.1021/acs.joc.7b03014
日期:2018.3.16
produce fluorinated and trifluoromethylated organic structures, the construction of difluoromethylated compounds remains a synthetic challenge. We have discovered that unactivated imines will react with difluoroenolates under exceedingly mild conditions when using magnesium salts and organic bases. We have applied this approach to the iminoaldol reaction to produce difluoromethylene groups as α,α-dif
Generation of formaldehyde and formaldehyde-d<sub>2</sub> for hydroxymethylations and hydroxydeuteromethylations of difluoroenolates and difluorobenzyl carbanions
作者:Hari R. Khatri、Changho Han、Reem A. Alkhodier、Amna T. Adam、Baharul Islam、David A. Colby
DOI:10.1039/d2cc01518h
日期:——
A method for the in situ production of formaldehyde from dimethylsulfoxide, bromine, and cesium carbonate is reported for reactions with difluoroenolates and difluorobenzyl carbanions. This process also generates formaldehyde-d2 for the production of 2,2-difluoro-1,1-deuteroethanols. Mechanistic and computational studies further characterize the production of hydroxymethylated and hydroxydeuteromethylated