Stereocontrolled 1,3-dipolar cycloadditions using Oppolzer's camphor sultam as the chiral auxiliary for carbonyl stabilized azomethine ylides

Efficient synthesis for each of the eight stereoisomers of the iminosugars lentiginosine and 1,4-dideoxy-1,4-imino-D-arabinitol (DAB)

Herein, we describe the efficient, diastereoselective syntheses of the iminosugars 1,4-dideoxy-1,4-imino-D-arabinitol (DAB) 1b, lentiginosine 3a, and the seven stereoisomers of each of these iminosugars starting from 4-benzoyl-6-deoxy-6-iodoglycopyranosides 47 with yields ranging from 38 % to 68 % for the DAB and isomers 1a-1h and from 44 % to 89 % for the lentiginosine and isomers 3a-3h. We also report the syntheses of the eight stereoisomers of the 4-benzoyl-6-deoxy-6-iodoglycopyranosides 47 from commercially available sugars. Key to the iminosugar syntheses is a single multistep reaction that converts the 4-benzoyl-6-deoxy-6-iodoglycopyranosides 47 to a vinyl pyrrolidine through a one-pot zinc mediated reductive elimination, followed by a reductive amination and finally an intramolecular nucleophilic substitution. Strategic selection of the amine utilized in the reductive amination and the functionalization of the intermediate carbon-carbon double bond provides access to a vast array of iminosugars.

Construction of thiazines and oxathianes via [3 + 3] annulation of N-tosylaziridinedicarboxylates and oxiranes with 1,4-dithiane-2,5-diol: application towards the synthesis of bioactive molecules

Efficient construction of functionalized thiazine and oxathiane derivatives via [3 + 3] annulation of N-tosylaziridinedicarboxylates and oxiranes with in situ generated mercaptoaldehyde in the presence of a Lewis acid is described.

Lewis acid-catalyzed [3 + 2]cyclo-addition of alkynes with N-tosyl-aziridines via carbon-carbon bond cleavage: synthesis of highly substituted 3-pyrrolines

A novel, efficient, and highly regioselective Lewis acid-catalyzed [3 + 2] cycloaddition of alkynes with azomethine ylides, which are easily obtained from N-tosylaziridines via C-C bond heterolysis at room temperature was developed. Moderate enantioselectivity (70% ee) can be achieved by the application of the commercially available chiral Pybox 7 as the ligand.

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.

Stereoselective cyclo-addition reactions of azomethine ylides catalysed by in situ generated Ag(I)/bisphosphine complexes

Stereoselective cyclo-addition reactions of azomethine ylides promoted by in situ generated Ag(I)/bisphosphine complexes were studied. Under the optimized conditions, the pyrrolidine products were isolated in up to 84 % yield and with up to 71% e.e. The effects of various reaction variables on the stereoselectivity were also investigated.

Azavinyl azomethine ylides from thermal ring opening of alpha-aziridinohydrazones: unprecedented 1,5-electrocyclization to imidazoles

Michael-type addition of aziridinecarboxylates to 1,2-diaza-1,3-butadienes under solvent-free conditions (SFC) resulted in the formation of alpha-aziridinohydrazone adducts. In toluene under reflux, alpha-aziridinohydrazones gave imidazoles in moderate to good yields. Such a reactivity pattern is explained by 1,5-electrocyclization of azavinyl azomethine ylide generated through thermal ring opening of alpha-aziridinohydrazones.

A formal [3+2] cycloaddition process with nonactivated aziridines to polysubstituted indolizidines

[chemical reaction: see text]. Heating a mixture of ethyl 7-iodo-2-heptynoate (or its analogues), 2-aryl aziridines, and K2CO3 in dry CH(3)CN delivers polysubstituted indolizidines. This reaction goes through an S(N)2/formal [3+2] cycloaddition process and represents the first synthetically useful example of the formal [3+2] cycloaddition process through a C-N bond cleavage of nonactivated aziridines.

Asymmetric Multicomponent [C+NC+CC] Synthesis of Highly Functionalized Pyrrolidines Catalyzed by Silver(I)

[reaction: see text] Highly functionalized pyrrolidines are obtained in a single chemical step via a mild, efficient, and selective Ag(I)-catalyzed asymmetric [C+NC+CC] coupling process. Oppolzer's camphorsultam enables the desired reaction cascade and provides a reliable means to control the developing stereochemistry and purify the products. This three-component reaction provides unprecedented access to structurally diverse pyrrolidines for both target- and diversity-oriented syntheses.

Stereoselective synthesis of N-alkylaziridines from N-chloroamines

We report the first racemic and stereoselective synthesis of cis- and trans-N-alkylaziridines viaN-chloroamines; using this methodology an N-3,4,5-trimethoxybenzylaziridine was synthesised and efficiently cleaved, affording the corresponding NH aziridine in high yield.

Bifunctional AgOAc-Catalyzed Asymmetric [3 + 2] Cycloaddition of Azomethine Ylides

[reaction: see text] A bifunctional AgOAc-catalyzed asymmetric cycloaddition of azomethine ylides with electronic-deficient alkenes was developed using ferrocenyloxazoline-derived N,P ligands. The reactive metal-bound azomethine ylide dipole is formed by the deprotonation with acetate, and extra base is not necessary. The reactions proceed with high enantioselectivity. This method provides an efficient and convenient route to optically active pyrrolidine derivatives.

Lewis acid-promoted carbon-carbon bond cleavage of aziridines: divergent cycloaddition pathways of the derived ylides

Lewis acids are shown to cleave the carbon-carbon bond of activated aziridines at ambient temperature. The derived metal-coordinated azomethine ylides undergo cycloaddition reactions with electron-rich alkenes. Cyclic alkenes afford products that are formally [4+2] adducts most likely derived from a Mannich-type addition to the ylide, followed by intramolecular Friedel-Crafts alkylation. Alternatively, acyclic alkenes undergo [3+2] cycloaddition to give new pyrrolidine products.

Aziridines: epoxides' ugly cousins?

Aziridines, the nitrogenous analogues of epoxides, have until recently excited far less interest amongst synthetic organic chemists than their oxygenated counterparts, with some justification. A range of reviews concerned with the physical properties, synthesis (asymmetric and otherwise), reactions and utility of aziridines exists; this review briefly summarizes the similarities and differences between oxiranes and their nitrogenated analogues, concentrating on the underlying properties of aziridines and recent developments in their chemistry. In addition to descriptions of the physical nature of aziridines, especially those features which underpin their utility as synthetic intermediates, the sections beneath describe reactions involving alkylative ring-opening and synthesis of aziridines.