Catalytic selective mono- and difluoroalkylation using fluorinated silyl enol ethers

This feature article highlights our recent achievements in catalytic selective mono- and difluoroalkylation using fluorinated silyl enol ethers (FSEEs).

Structure–property relation and third-order nonlinear optical studies of two new halogenated chalcones

In the present work, the crystal structure and third-order nonlinear optical (NLO) properties of two novel chalcone derivatives namely (E)-3-(4-bromo-2-fluorophenyl)-1-(3,4-dimethoxyphenyl)prop-2-en-1-one (I) and (E)-3-(4-bromophenyl)-1-(3,4-dimethoxyphenyl)prop-2-en-1-one (II) are investigated by analyzing the packing pattern, intermolecular interaction, Hirshfeld surface analysis and standard Z-scan technique with continuous wave laser at 532 nm. Both compounds are donor-acceptor-acceptor (D–A–A) type intramolecular charge transferring molecule which crystallized in centrosymmetric space group. The existence of C–H···O hydrogen bonds in I and Br···O short contact interactions in II play important roles in their packing pattern and NLO properties. The molecules reveal a strong nonlinear refraction (NLR) and nonlinear susceptibility χ (3) when the donor and acceptor are arranged side-by-side as in compound I. And as the donor and acceptor are aligned on a head-to-head alignment, the molecules divulge a strong third-order nonlinear absorption (NLA) and limiting threshold (LT). The Z-scan results indicate that both compounds would be potential applicants in the development of NLO devices.

Catalytic Enantioselective Michael Addition Reactions of Tertiary Enolates Generated by Detrifluoroacetylation

This work describes, for the first time, Michael addition reactions of tertiary fluoro-enolates in situ generated by detrifluoroacetylation with 1-(1-(phenylsulfonyl) vinylsulfonyl)benzene. Excellent enantioselectivity and chemical yields were achieved with application of catalysts (10 mol %) derived from Cu(OTf)₂ and (1S,2S)-1,2-diphenylethane-1,2-diamine. These reactions show a considerable degree of structural generality and allow the preparation of new types of biologically relevant molecules that contain quaternary C-F stereogenic carbon atoms and feature five-, six-, or seven-membered rings as well as heterocyclic 3-fluoro-2,3-dihydrochromen-4-one moieties.

In situ formed acetals facilitated direct Michael addition of unactivated ketones

A facile Michael addition of unactivated ketones under Brønsted acid conditions for the synthesis of 1,5-diketones.

Direct Catalytic Asymmetric Mannich-Type Reaction of α- and β-Fluorinated Amides

The last two decades have witnessed the emergence of direct enolization protocols providing atom-economical and operationally simple methods to use enolates for stereoselective C-C bond-forming reactions, eliminating the inherent drawback of the preformation of enolates using stoichiometric amounts of reagents. In its infancy, direct enolization relied heavily on the intrinsic acidity of the latent enolates, and the reaction scope was limited to readily enolizable ketones and aldehydes. Recent advances in this field enabled the exploitation of carboxylic acid derivatives for direct enolization, offering expeditious access to synthetically versatile chiral building blocks. Despite the growing demand for enantioenriched fluorine-containing small molecules, α- and β-fluorinated carbonyl compounds have been neglected in direct enolization chemistry because of the competing and dominating defluorination pathway. Herein we present a comprehensive study on direct and highly stereoselective Mannich-type reactions of α- and β-fluorine-functionalized 7-azaindoline amides that rely on a soft Lewis acid/hard Brønsted base cooperative catalytic system to guarantee an efficient enolization while suppressing undesired defluorination. This protocol contributes to provide a series of fluorinated analogs of enantioenriched β-amino acids for medicinal chemistry.

Fluorinated enol ethers: their synthesis and reactivity

This review sums up the methods for the preparation of fluorinated enol ethers as well as their numerous synthetic applications.