Highly Stereoselective Synthesis of Stereochemically Defined Polyhydroxylated Propargylamines by Alkynylation ofN-Benzylimines Derived from (R)-Glyceraldehyde

Diastereoselective C-alkylation of aldimines, derived from chiral α-carbon heteroatom-substituted aldehydes, with triethylborane. Application to the synthesis of benzylisoquinolines

The one-pot reaction of a chiral aldehyde, p-methoxyaniline or p-fluoroaniline, and triethylborane produces the corresponding alkylated chiral amine with high yields and diastereoisomeric ratios. Stereocontrol is induced by the presence of a heteroatom in the α-position to the aldehyde. In the case of alkylation of imines derived from chiral aliphatic amines, good yields and moderate to high diastereoselectivity are obtained: yields are significantly better when the preformed imine is used in the reaction with triethyl borane, and diastereoselectivity of the reactions largely depends on the structure of the chiral aliphatic amine. The methodology is successfully applied to the synthesis of romneine, a natural benzylisoquinoline.

Structures and Reactivities of Sodiated Evans Enolates: Role of Solvation and Mixed Aggregation on the Stereochemistry and Mechanism of Alkylations

Oxazolidinone-based sodiated enolates (Evans enolates) were generated using sodium diisopropylamide (NaDA) or sodium hexamethyldisilazide (NaHMDS) in the presence of N,N,N',N'-tetramethylethylenediamine (TMEDA), ( R,R)- trans- N,N,N',N'-tetramethylcyclohexanediamine [( R,R)-TMCDA], or ( S,S)-TMCDA. 13C NMR spectroscopic analysis in conjunction with the method of continuous variations (MCV), x-ray crystallography, and density functional theory (DFT) computations revealed the enolates to be octahedral bis-diamine-chelated monomers. Rate and computational studies of an alkylation with allyl bromide implicate a bis-diamine-chelated-monomer-based transition structure. The sodiated Evans enolates form mixed dimers with NaHMDS, NaDA, or sodium 2,6-di- tert-butylphenolate, the reactivities of which are examined. Stereoselective quaternizations, aldol additions, and azaaldol additions are described.

Synthesis and Reactivity of Propargylamines in Organic Chemistry

Propargylamines are a versatile class of compounds which find broad application in many fields of chemistry. This review aims to describe the different strategies developed so far for the synthesis of propargylamines and their derivatives as well as to highlight their reactivity and use as building blocks in the synthesis of chemically relevant organic compounds. In the first part of the review, the different synthetic approaches to synthesize propargylamines, such as A³ couplings and C-H functionalization of alkynes, have been described and organized on the basis of the catalysts employed in the syntheses. Both racemic and enantioselective approaches have been reported. In the second part, an overview of the transformations of propargylamines into heterocyclic compounds such as pyrroles, pyridines, thiazoles, and oxazoles, as well as other relevant organic derivatives, is presented.

Copper(ii) carboxymethylcellulose (CMC-CuII) as an efficient catalyst for aldehyde–alkyne–amine coupling under solvent-free conditions

A novel heterogeneous Cu(ii) carboxymethylcellulose catalyst was prepared and successfully employed in the A3 coupling without using any co-catalyst, other additives, bases under solvent-free conditions.

Aldehyde–alkyne–amine (A3) coupling catalyzed by a highly efficient dicopper complex

A dicopper(i) complex was developed as highly efficient catalyst for A³ coupling reactions, which led to the formation of propargylamines.

Stereoselective synthesis and biological evaluation of D-fagomine, D-3-epi-fagomine and D-3,4-epi-fagomine analogs from D-glyceraldehyde acetonide as a common building block

The stereoselective synthesis of D-fagomine, D-3-epi-fagomine, and D-3-epi-fagomine analogs starting from readily available D-glyceraldehyde acetonide has been achieved. The synthesis involves diastereoselective anti-vinylation of its homoallylimine, ring-closing metathesis, and stereoselective epoxidation followed by regioselective ring-opening or stereoselective dihydroxylation. The lack of a strong activity as glycosidase inhibitors of these compounds could be advantageous for their therapeutic use as chaperones.