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.     

Thiourea-catalyzed asymmetric formal [3+2] cycloaddition of azomethine ylides with nitroolefins

A chiral thiourea catalyst possessing an amine function catalyzes an asymmetric [3+2] cycloaddition of azomethine ylides to nitroolefins to provide highly functionalized pyrrolidines with high diastereo- and enantioselectivities (up to 98:1:1 dr, 92% ee). The reaction proceeds in a stepwise manner consisting of Michael addition and subsequent intramolecular aza-Henry reaction. Both reactions are promoted by the thiourea catalyst, and the reaction rate of the latter step is efficiently enhanced by the addition of 2,2,2-trifluoroethanol.     

AgOAc catalyzed asymmetric [3+2] cycloaddition of azomethine ylides with chiral ferrocene derived P,S ligands

Ferrocene derived P,S-heterodonor ligands were effectively used in AgOAc catalyzed asymmetric cycloaddition of azomethine ylides. The roles of planar chirality and electronic properties of the phosphorous substituents have been examined, and up to 93% ee was obtained.     

Highly enantioselective catalytic [6+3] cycloadditions of azomethine ylides

Under control: Highly functionalized chiral annulated piperidines with eight stereocenters are efficiently obtained by means of a highly enantioselective one-pot [6+3]/[4+2] sequence. This sequence included the first enantioselective [6+3] cycloaddition of azomethine ylides with fulvenes.     

Microwave-assisted [3 + 2] cycloadditions of azomethine ylides

The microwave-assisted intramolecular [3 + 2] cycloaddition reaction of azomethine ylides to activated and nonactivated alkenes and alkynes is described. The procedure allows the synthesis of pyrrolidines and pyrrole products in good to excellent overall yields in short reaction times. It appears from parallel comparative studies that the microwave procedure favors the reaction times and overall purity of the crude reaction mixture. The reactions can also be performed in the absence of solvent. [reaction: see text]     

First example of [3+2] cycloaddition of azomethine ylides to 5-methylidene-3-phenylhydantoin

Russian Chemical Bulletin - New type dispiroindolinones, dispiroimidazolidine-4,3′-pyrrolidine-2′,3″-indolinones unsubstituted at position 4′ of the central pyrrolidine...     

Highly enantioselective Ag(i)-catalyzed [3 + 2] cycloaddition of azomethine ylides

A highly reactive Ag(I)-catalyzed [3 + 2] cycloaddition of azomethine ylides is founded using AgOAc as the catalytic precursor and phosphines as ligands. Using a new bis-ferrocenyl amide phosphine (FAP) as the ligand, we found that high enantioselectivities (up to 97% ee) have been achieved in the [3 + 2] cycloaddition of azomethine ylides. Up to four stereogenic centers can be established in this multicomponent coupling reaction from readily available materials such as aldehydes, aminoesters, and dipolarophiles.     

The catalytic asymmetric 1,3-dipolar cycloaddition of ynones with azomethine ylides

The first catalytic asymmetric 1,3-dipolar cycloaddition of electron-deficient carbon-carbon triple bonds with azomethine ylides has been established. This reaction provides an unprecedented approach to access novel 2,5-dihydropyrrole derivatives with potential bioactivities in perfect enantioselectivities of up to >99% ee.     

The Lewis acid-catalyzed [3+1+1] cycloaddition of azomethine ylides with isocyanides

A Lewis acid-catalyzed [3+1+1] cycloaddition reaction between aliphatic isocyanides and azomethine ylides generated in situ from aziridines, leading to pyrrolidine derivatives, has been developed. This reaction proceeds smoothly under mild conditions and can also be modified by employing aromatic isocyanides to generate four-membered heterocycles, azetidines, through a [3+1] cycloaddition reaction.     

Intramolecular [3+2] cycloadditions of functionalized azomethine ylides

The use of dithiane chemistry to synthesize functionalized azomethine ylides which are then employed in [3+2] cycloaddition chemistry is described. The advantages of this methodology as well as an approach to the lycorenine alkaloid system are presented.     

N-(2-pyridylmethyl)imines as azomethine precursors in catalytic asymmetric [3 + 2] cycloadditions

An efficient Cu(I)-catalyzed asymmetric [3 + 2] cycloaddition of N-(2-pyridylmethyl) imines has been developed. In the presence of a Cu(CH(3)CN)(4)PF(6)/bisoxazoline catalyst system, high levels of enantioselectivity (up to 97% ee) and moderate to high exo selectivity were achieved with a wide variety of substituted dipolarophiles, including maleimides, fumarates, fumarodinitrile, enones, and nitroalkenes. The reaction with unsymmetrically substituted dipolarophiles is completely regioselective.     

Catalytic asymmetric [3+2] cycloaddition of azomethine ylides. Development of a versatile stepwise,three-component reaction for diversity-oriented synthesis

We report a new catalyst system that should enhance the use of enantioselective 1,3-dipolar cycloadditions of azomethine ylides with electronic-deficient olefins in the divergent pathways of diversity-oriented synthesis (DOS). The underlying reaction is of considerable interest in DOS because its stereospecificity enables stereochemical diversification of up to four tetrahedral centers on pyrrolidine rings. This new catalyst system extends the scope and selectivity of the azomethine ylide cycloaddition and is compatible with reagents used in a one-bead/one-stock solution technology platform for DOS.     

A facile synthesis of novel dispiroheterocycles through solvent-free microwave-assisted [3+2] cycloaddition of azomethine ylides

A comparative study of the synthesis of novel dispiro pyrrolo/pyrrolizidino ring systems by the cycloaddition of azomethine ylides generated by a decarboxylative route from sarcosine/proline and isatin with the dipolarophile 9-arylidine-fluorene using four different methodologies is described. A solvent-free microwave-assisted approach gave products with the highest yields in a short time. Additionally, our solvent-free approach allowed the use of 4-N,N-dimethylaminobenzaldehyde, which failed to yield the desired cycloadducts under conventional approaches.     

Organocatalytic enantioselective (3+2) cycloaddition using stable azomethine ylides

We have developed a highly efficient procedure for carrying out the catalytic enantioselective (3+2) cycloaddition between enals and stable azomethine ylides such as isoquinolinium and phthalizinium methylides. Under the optimized reaction conditions highly substituted chiral pyrroloisoquinolines and pyrrolophthalazines have been obtained in high yields and excellent diastereo- and enantioselectivities.     

Cu(I)-catalyzed highly exo-selective and enantioselective [3 + 2] cycloaddition of azomethine ylides with acrylates

[reaction: see text] A novel Cu(I)-catalyzed asymmetric 1,3-dipolar cycloaddition of azomethine ylides with acrylates has been developed. Up to 98/2 exo/endo selectivity and up to 98% enantiomeric excess have been achieved.     

Palladium-catalyzed asymmetric [3 + 2] trimethylenemethane cycloaddition reactions

Transition-metal-catalyzed trimethylenemethane (TMM) [3 + 2] cycloadditions provide direct routes to functionalized cyclopentanes. This reaction has been shown to be a highly chemo-, regio-, and diastereoselective process. We report a palladium-catalyzed asymmetric [3 + 2] trimethylenemethane (TMM) cycloaddition between 3-acetoxy-2-trimethylsilylmethyl-1-propene and various di- and trisubstituted olefins. Yields of exo-methylenecyclopentane products range from 59 to 99%, and enantiomeric excesses range from 58 to 92% ee.     

New chiral ferrocenyl P,S-ligands for highly diastereo- and enantioselective Ag(I)-catalyzed asymmetric [3+2] cycloaddition of azomethine ylides

A new family of chiral ferrocenyl P,S-ligands incorporating an indole ring at the α-ferrocenylmethyl position has been prepared via a Friedel–Crafts alkylation reaction of (R_c,S_Fc)-PPFA with a variety of 2-indole thioethers. These newly developed ferrocenyl P,S-ligands proved to be efficient in the AgOAc-catalyzed asymmetric [3+2] cycloaddition of azomethine ylides with various dipolarophiles, giving cycloadducts with high diastereoselectivities and enantioselectivities (up to 99% ee).     

A convenient procedure for the catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides and alkenes

[reaction: see text] Silver fluoride and cinchona alkaloids catalyze the diastereo- and enantioselective 1,3-dipolar cycloaddition between azomethine ylides, generated from N-alkylideneglycine esters, and acrylates to give the corresponding endo-adducts. Azomethine ylides derived from aromatic and aliphatic aldehydes react in a highly diastereoselective reaction with good yields and enantioselectivities of the substituted pyrrolidines.