Oxazolidine Ring Opening and Isomerization to (E)-Imines. Asymmetric Synthesis of Aryl-α-fluoroalkyl Amino Alcohols

Electrochemical tandem trifluoromethylation of allylamines/formal (3 + 2)-cycloaddition for the rapid access to CF3-containing imidazolines and oxazolidines

A straightforward and environmentally friendly synthesis of CF₃-containing imidazolines and oxazolidines has been developed through an electrochemical three-component reaction among allylamines, the Langlois reagent, and nitrile or carbonyl compounds.

Palladium-catalyzed three-component tandem cyclization of buta-2,3-dien-1-ol, aryl iodides, and imines: an efficient protocol for the synthesis of oxazolidine derivatives

An efficient three-component tandem cyclization reaction for the synthesis of highly substituted oxazolidines was achieved through the Pd⁰-catalyzed cyclization of buta-2,3-dien-1-ol with aryl iodides and imines.

Palladium-catalyzed vicinal amino alcohols synthesis from allyl amines by in situ tether formation and carboetherification

Vicinal amino alcohols are important structural motifs of bioactive compounds. Reported herein is an efficient method for their synthesis based on the palladium-catalyzed oxy-alkynylation, oxy-arylation, or oxy-vinylation of allylic amines. High regio- and stereoselectivity were ensured through the in situ formation of a hemiaminal tether using the cheap commercially available trifluoroacetaldehyde in its hemiacetal form. The obtained compounds are important building blocks, which can be orthogonally deprotected to give either free alcohols, amines, or terminal alkynes.

Redox-neutral α-oxygenation of amines: reaction development and elucidation of the mechanism

Cyclic secondary amines and 2-hydroxybenzaldehydes or related ketones react to furnish benzo[e][1,3]oxazine structures in generally good yields. This overall redox-neutral amine α-C-H functionalization features a combined reductive N-alkylation/oxidative α-functionalization and is catalyzed by acetic acid. In contrast to previous reports, no external oxidants or metal catalysts are required. Reactions performed under modified conditions lead to an apparent reductive amination and the formation of o-hydroxybenzylamines in a process that involves the oxidation of a second equivalent of amine. A detailed computational study employing density functional theory compares different mechanistic pathways and is used to explain the observed experimental findings. Furthermore, these results also reveal the origin of the catalytic efficiency of acetic acid in these transformations.

Nickel(II)-catalyzed diastereoselective [3+2] cycloaddition of N-tosyl-aziridines and aldehydes via selective carbon-carbon bond cleavage

An efficient and mild Ni(ClO(4))(2)-catalyzed [3+2] cycloaddition of N-tosylaziridines and aldehydes via C-C bond cleavage was developed. The cycloaddition reaction proceeds with high diastereoselectivity and regioselectivity leading to highly substituted 1,3-oxazolidines. Notably, this novel reaction can be easily expanded to gram level scale and the thermal conditions cannot achieve the same transformation.

Fluorine... and pi...alkali metal interactions control in the stereoselective amide enolate alkylation with fluorinated oxazolidines (Fox) as a chiral auxiliary: an experimental and theoretical study

The alpha-alkylation of amide enolates by using a pseudo-C(2) symmetry trans 4-phenyl-2-trifluoromethyloxazolidine (trans-Fox) as a chiral auxiliary occurs with an extremely high diastereoselectivity (>99 % de). The origin of this excellent stereocontrol was investigated by an experimental and theoretical (DFT) study. With this trans chiral auxiliary, both F...metal and pi...metal interactions compete to give the same diastereomer through Re face alkylation of the enolate. A 5.5 kcal mol(-1) energy difference found between the Re face and the Si face attack transition states is consistent with the complete diastereoselectivity that has been experimentally achieved. On the other hand, in the case of the cis chiral auxiliary (cis-Fox) the competition between the F...metal and pi...metal interactions is unfavourable to the diastereoselectivity. In this case, the Re face and the Si face attack transition states were found to be nearly isoenergetic (0.3 kcal mol(-1) difference), which is in good agreement with the very low diastereoselectivity observed.

Asymmetric Syntheses of 1-Aryl-2,2,2-trifluoroethylamines via Diastereoselective 1,2-Addition of Arylmetals to 2-Methyl-N-(2,2,2-trifluoroethylidene)propane-2-sulfinamide

Condensation of N-tert-butanesulfinamide (S)-1 with trifluoroacetaldehyde hydrate 2a afforded 2-methyl-N-(2,2,2-trifluoroethylidene)propane-2-sulfinamide 3. Without isolation and purification, imine 3 was added to various aryllithium reagents to give highly diastereomerically enriched adducts 5a-g. Acidic methanolysis of 5a-g provided the desired 1-aryl-2,2,2-trifluoroethylamine hydrochloride compounds 6a-g. [reaction: see text].

Catalytic Asymmetric Synthesis of α,α,α-Trifluoromethylamines by the Copper-Catalyzed Nucleophilic Addition of Diorganozinc Reagents to Imines

[reaction: see text] A copper-catalyzed asymmetric addition of diorganozinc reagents to N-phosphinoylimines has been developed for the synthesis of chiral alpha,alpha,alpha-trifluoromethylamines. The trifluoromethyl ketimines, generated in situ from the corresponding hemiaminals, led to the chiral amides in high yields (71-89%) and excellent enantiocontrol (91-99% ee).

Diastereoselective Arylithium Addition to an α-Trifluoromethyl Imine. Practical Synthesis of a Potent Cathepsin K Inhibitor

A practical, chromatography-free synthesis of potent cathepsin K inhibitor 1 is described. The addition of 4-bromophenyllithium to an alpha-trifluoromethylimine derived from commercially available (S)-leucinol was accomplished in a highly diastereoselective manner (97.6% de, 91% yield). Subsequent Suzuki cross-coupling afforded biaryl 7. Oxidation of the alcohol and sulfide functionalities led to the formation of carboxylic acid 8. Crystallization of 7 and acid 8 as its dicyclohexylamine salt gave excellent impurity rejection. The final amide coupling with commercially available aminoacetonitrile hydrochloride afforded 1 in excellent purity (99.6A% by HPLC, 100% de, <3 ppm Pd, W, Cr).

Identification of a potent and selective non-basic cathepsin K inhibitor

Based on our previous study with trifluoroethylamine as a P2-P3 amide isostere of cathepsin K inhibitor, further optimization led to identification of compound 22 (L-873724) as a potent and selective non-basic cathepsin K inhibitor. This compound showed excellent pharmacokinetics and efficacy in an ovariectomized (OVX) rhesus monkey model. The volumes of distribution close to unity were consistent with this compound not being lysosomotropic, which is a characteristic of basic cathepsin K inhibitors.

Convenient Asymmetric Synthesis of β-Trifluoromethyl-β-amino Acid, β-Amino Ketones, and γ-Amino Alcohols via Reformatsky and Mannich-Type Reactions from 2-Trifluoromethyl-1,3-oxazolidines

The stereoselective syntheses of beta-trifluoromethyl-beta-amino ester, beta lactams, and beta-amino ketones starting from an oxazolidine derived from trifluoroacetaldehyde hemiacetal and (R)-phenylglycinol are reported. The Mannich-type reaction involving a chiral fluorinated iminium ion occurred in a good yield and with a higher stereoselectivity (dr up to 96:4) than that of the Reformatsky-type reaction. This straightforward strategy was applied to the short syntheses of (R)-3-amino-4,4,4-trifluorobutanoic acid, a series of novel enantiopure unprotected fluorinated beta-amino ketones, and their corresponding gamma-amino alcohols.

Trifluoroethylamines as amide isosteres in inhibitors of cathepsin K

The P2-P3 amide of dipeptide cathepsin K inhibitors can be replaced by the metabolically stable trifluoroethylamine group. The non-basic nature of the nitrogen allows the important hydrogen bond to Gly66 to be made. The resulting compounds are 10- to 20-fold more potent than the corresponding amide derivatives. Compound 8 is a 5 pM inhibitor of human cathepsin K with >10,000-fold selectivity over other cathepsins.

The chemistry of trifluoromethyl imines and related acetals derived from fluoral

Trifluoromethylated nitrogen-containing molecules have been shown to have important biological effects and their synthesis is in the focus of the pharmaceutical industry. In the last few years, simple nitrogen derivatives of fluoral, i.e. imines, acetals and oxazolidines, have emerged as powerful building blocks to synthesize these target molecules and relevant precursors. This review summarizes the chemistry of these "N-derivatives of fluoral", with special highlight on the syntheses of peptidomimetic units (amino alcohols, amino acids...) and heterocycles (piperidines, beta-lactams...).

Titanium Catalysis in the Ugi Reaction of α-Amino Acids with Aromatic Aldehydes

[reaction: see text] Ugi reaction between an (S)-alpha-amino acid, an aromatic aldehyde, and an isonitrile proceeds best under catalysis by TiCl(4) in MeOH. The sense of diastereoinduction is (S,S).