Magnesium-Promoted Additions of Difluoroenolates to Unactivated Imines

Synthesis of α,α-Difluoro-β-amino Ketones from N-Boc-α-Amidosulfones and Pentafluoro-gem-diols

To circumvent the synthesis and isolation of imines, a method was devised to construct α,α-difluoro-β-amino ketones from N-Boc-α-amidosulfones. The reactive nucleophiles, difluoroenolates, are generated in situ from the pentafluoro-gem-diols using cesium fluoride in pyridine. NMR studies confirm the role of the α-amidosulfones in this process. Incubation of the α,α-difluoro-β-amino ketones in rat serum demonstrates the relative stability of this structure as well as its value as a chemical probe or lead.

Transient Formation of Hemiketals from Pentafluoro-gem-diols in the Presence of Alcohols

Pentafluoro-gem-diols have emerged as a source of reactive intermediates for synthesizing fluorinated molecules. When pentafluoro-gem-diols were exposed to alcohols as solvents, the formation of transient hemiketals was detected by 19F NMR. The conversion rates to hemiketals were found to be higher with primary alcohols than with secondary or fluorinated alcohols. These findings provide valuable insight for developing novel techniques to construct intricate fluorinated structures using pentafluoro-gem-diols.

Generation of formaldehyde and formaldehyde-d2 for hydroxymethylations and hydroxydeuteromethylations of difluoroenolates and difluorobenzyl carbanions

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 difluorinated organic molecules.

Recent progress in the chemistry of β-aminoketones

The current study highlighted the significance of β-aminoketones as privileged biologically active molecules, recent synthetic strategies, and synthetic applications.

Synthesis of Difluorinated Halohydrins by the Chemoselective Addition of Difluoroenolates to α-Haloketones

α-Haloketones are valuable intermediates in the synthesis of pharmaceuticals and natural products because they display two electrophiles. Although chemoselective additions to each of these functional groups are known, the use of fluorinated nucleophiles has not been characterized, except for the dimerization of fluorohalomethyl ketones. Our studies demonstrate the use of difluoroenolates to create difluorinated bromohydrins and chlorohydrins from α-haloketones without any cyclization or rearrangement due to the mild conditions.

Difluoroisoxazolacetophenone: A Difluoroalkylation Reagent for Organocatalytic Vinylogous Nitroaldol Reactions of 1,2-Diketones

Difluoroisoxazolacetophenone (DFIO) is developed as a new difluoroalkylation reagent that can be easily prepared from inexpensive starting materials. In situ remote C-C bond cleavage of DFIO affords γ,γ-difluoroisoxazole nitronate that undergoes base-catalyzed vinylogous nitroaldol additions to isatins, benzothiophene-2,3-dione, unsaturated-α-ketoesters, and cyclic 1,2-diketones. This organocatalytic debenzoate vinylogous nitroaldol reaction provides a new and mild approach for the preparation of various difluoroisoxazole-substituted 3-hydroxy-2-oxindoles.

Microwave-Assisted Copper Catalysis of α-Difluorinated gem-Diol toward Difluoroalkyl Radical for Hydrodifluoroalkylation of para-Quinone Methides

Reported herein is a unified strategy to generate difluoroalkyl radicals from readily prepared α-difluorinated gem-diols by single electron oxidation. Under microwave irradiation, a catalytic amount of oxidant Cu(OAc)₂ succeeds in the formation of transient difluoroalkyl radicals in situ, for the first time. The reaction features a simple protocol, short reaction time, scalability, and high yield. The synthetic utility of this new methodology was also explored for the synthesis of difluoroalkylated spiro-cyclohexadienones, which is an important core structure in natural products and pharmaceuticals.

Controlling the Cleavage of Carbon-Carbon Bonds To Generate α,α-Difluorobenzyl Carbanions for the Construction of Difluoromethylbenzenes

Controlling the cleavage of carbon-carbon bonds during a chemical reaction is a substantial challenge; however, synthetic methods that accomplish this objective produce valuable and often unexplored reactivity. We have designed a mild process to generate α,α-difluorobenzyl carbanions in the presence of potassium carbonate by exploiting the cleavage of C-C bonds during the release of trifluoroacetate. The initiating reagent is potassium carbonate, which represents an improvement over existing protocols that require a strong base. Fragmentation studies across substituted arenes and heteroarenes were conducted along with computational analyses to elucidate reactivity trends. Furthermore, the mildly generated α,α-difluorobenzyl carbanions from electron-deficient aromatics and heteroaromatic rings can react with aldehydes to create derivatives of difluoromethylbenzenes, which are valuable synthetic targets.

Chemistry of detrifluoroacetylativelyin situgenerated fluoro-enolates

This review article provides a summary of the detrifluoroacetylativein situgeneration of fluorine-containing enolates and their related reactions.

A Sc(OTf)3 catalyzed Mukaiyama–Mannich reaction of difluoroenoxysilanes with unactivated ketimines

The first example of a Mukaiyama–Mannich reaction of difluoroenoxysilanes with unactivated ketimines catalyzed by Sc(OTf)₃ is described.

Agonists of the γ-aminobutyric acid type B (GABAB) receptor derived from β-hydroxy and β-amino difluoromethyl ketones

β-Hydroxy difluoromethyl ketones represent the newest class of agonists of the GABA-B receptor, and they are structurally distinct from all other known agonists at this receptor because they do not display the carboxylic acid or amino group of γ-aminobutyric acid (GABA). In this report, the design, synthesis, and biological evaluation of additional analogues of β-hydroxy difluoromethyl ketones characterized the critical nature of the substituted aromatic group on the lead compound. The importance of these new data is interpreted by docking studies using the X-ray structure of the GABA-B receptor. Moreover, we also report that the synthesis and biological evaluation of β-amino difluoromethyl ketones provided the most potent compound across these two series.

Divergent Reactivity of gem-Difluoro-enolates toward Nitrogen Electrophiles: Unorthodox Nitroso Aldol Reaction for Rapid Synthesis of α-Ketoamides

An amination reaction of in situ generated gem-difluoro-enolates has been explored with electrophilic nitrogen sources. While their exposure to azodicarboxylates smoothly produced fluorinated α-amino ketones, reaction with nitrosoarenes (nitroso aldol reaction) furnished α-ketoamides in very high yields (up to 94%). The reaction is very fast (typically completed within 5 min) and scalable and tolerates various sensitive functional groups. Synthetic utility of this process was highlighted through the production of diverse nitrogen heterocycles and an orexin receptor antagonist.