The Catalytic Mannich Reaction of 1,1-Difluoro-2-trialkyl(aryl)silyl-2-trimethyl-silyloxyethenes: Preparation of β-Amino Acid Derivatives

Superacid-Synthesized Fluorinated Diamines Act as Selective hCA IV Inhibitors

Carbonic anhydrase (CA) IV is a membrane-bound enzyme involved in important physio-pathological processes, such as excitation-contraction coupling in heart muscle, central nervous system (CNS) extracellular buffering, and mediation of inflammatory response after stroke. Known since the mid-1980s, this isoform is still largely unexplored when compared to other isoforms, mostly for the current lack of inhibitors targeting selectively this isoform. The discovery of selective CA IV inhibitors is thus largely awaited. In this work, we report β-(di) fluoropropyl diamines as effective CA IV inhibitors, opening real perspectives for a new mode of selective inhibition of this isoform. Inhibition data reveal that the essential structure core to ensure a potent and selective inhibition of CA IV is the N-propyldiamine. Molecular modeling studies were employed to understand the binding mode of the synthesized amines. Conformational searches within the active site space carried out in an implicit solvent (water) model were also conducted.

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).

Designing a novel tetradentate polyoxometalate eco-catalyst for the synthesis of β-aminocyclohexanone derivatives in water

The synthesis of a series of known β-aminocyclohexanones has been accomplished using pentaerythrityl tetramethyl imidazolium phosphotungstate (C(MIM-PTA)₄) as a new tetradentate acidic catalyst. It was prepared via condensation of pentaerythrityl tetrabromide with methyl imidazole. Then, bulky anion H₂PW₁₂O₄₀¹⁻ was substituted with Br⁻ in the structure. This tetradentate catalyst provides designable cations and anions. Anions have two types of acids, acidic protons, and metals with Lewis acidity. In order to test the efficient catalytic behavior of the tetradentate catalyst, a controlled reaction was performed using benzaldehyde, aniline and cyclohexanone. Imine from the condensation of benzaldehyde and aniline was observed in the absence of ionic catalyst instead of desired products. Thus, this reaction would be attractive because of the time, energy, and raw material saving considerations because of the absence of isolation of intermediates and stereospecificity. The catalyst shows high catalytic activity such that after four recycles the product was obtained with high yield and purity. This reaction was performed at room temperature. Although high temperature could improve the reaction rate, it contributes to side reactions and oxidation of aldehyde and amine. The catalyst was characterized by elemental analysis, FT-IR spectroscopy, ¹H NMR, ¹³C NMR, and TGA.

The synthesis of a series of known β-aminocyclohexanones has been accomplished using pentaerythrityl tetramethyl imidazolium phosphotungstate (C(MIM-PTA)₄) as a new tetradentate acidic catalyst.

Neighboring phenolic group-activated gem-difluoroallylboration of imines for the catalyst-free synthesis of gem-difluorohomoallylamines

An unprecedented imine allylation with pinacol gem-difluoroallylborates for the synthesis of a wide range of racemic gem-difluorohomoallylamine derivatives under catalyst-free conditions was enabled by a neighboring phenolic group in an N-protecting group.

A general and efficient Lewis acid catalysed Mukaiyama-aldol reaction of difluoroenoxysilanes and ketones

We report a general and highly efficient Mukaiyama-aldol reaction of ketones and difluoroenoxysilanes. While the reaction of aryl ketones worked efficiently in the presence of Bi(OTf)₃, that of aliphatic ketones required the use of Sc(OTf)₃. In addition, Sc(OTf)₃ was capable of achieving excellent 1,2-selectivity in the corresponding reaction of α,β-unsaturated ketones. This method provides a facile access to differently substituted β-hydroxy α,α-difluoro ketones, versatile synthons for difluomethylated tertiary alcohols.

A highly efficient Mukaiyama–Mannich reaction of N-Boc isatin ketimines and other active cyclic ketimines using difluoroenol silyl ethers catalyzed by Ph3PAuOTf

A Ph₃PAuOTf catalyzed highly efficient reaction of difluoroenoxysilanes and active ketimines is reported, which represents the first Au(i)-catalyzed Mukaiyama–Mannich reaction.

One-pot three-component Mannich-type reactions using sulfamic acid catalyst under ultrasound irradiation

Sulfamic acid (NH(2)SO(3)H, SA) was used as an efficient, inexpensive, non-toxic and recyclable green catalyst for the ultrasound-assisted one-pot Mannich reaction of aldehydes with ketones and amines. This ultrasound protocol has advantages of high yield, mild condition, no environmental pollution, and simple work-up procedures. Most importantly, beta-aminocarbonyl compounds with ortho-substituted aromatic amines are obtained in acceptable to good yields by this methodology for the first time.

An Easy Stereoselective Access to β,γ-Aziridino α-Amino Ester Derivatives via Mannich Reaction of Benzophenone Imines of Glycine Esters with N-Sulfonyl α-Chloroaldimines

Mannich-type addition of benzophenone imine glycinates across newly synthesized N-(p-toluenesulfonyl) alpha-chloroaldimines afforded gamma-chloro-alpha,beta-diamino ester derivatives with moderate diastereoselectivity as separable mixtures of anti and syn diastereomers. The gamma-chloro-alpha,beta-diamino esters were efficiently cyclized under basic conditions to the corresponding beta,gamma-aziridino alpha-amino ester derivatives, representing a new class of conformationally constrained heterocyclic alpha,beta-diamino acid derivatives. The relative configuration of the aziridines was determined via X-ray diffraction analysis. Mechanisms and intermediate transition states to explain the stereochemical outcome of the Mannich reaction with different substrates or under different conditions are proposed. The synthetic importance of the beta,gamma-aziridino alpha-amino ester derivatives is demonstrated by their conversion into the corresponding Boc-protected derivatives and ring opening reactions to alpha,beta-diamino esters and a gamma-amino alpha,beta-unsaturated amino ester.