A series of 1,3-dipolar cycloaddition reactions are carried out using cyclodimers of simple nitrones and various dipolarophiles; substituted isoxazolidines are isolated and identified. It is proved that such cyclodimers, in solution, are in equilibrium with their corresponding nitrones and enamines. It is also concluded that aldocyclodimers are more potent than keto-cyclodimers in establish...

Abstract One-pot two sequential [3 + 2] cycloadditions of azomethine ylides with different dipolarophiles for diastereoselective synthesis spirooxindole pyrrolizidines are introduced. This one-pot involving five components generates a highly condensed ring system bearing seven stereocenters diastereoselectively. The new method has high pot, atom, and step economy. Only equivalents water release...

N-Alkylation of optically active 1-benzyl-4-phenyl-4,5-dihydroimidazole with active alkyl halides and treatment of the so-formed 4,5-dihydroimidazolium ions with DBU in the presence of a range of electron-deficient alkene dipolarophiles, constitutes a 'one-pot' cascade terminating in a 1,3-dipolar cycloaddition reaction that affords optically active pyrrolo[1,2-a]imidazoles. Three bonds of the ...

the reaction of bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (curcumin) and two novel ligands of bis[4-tetrabenzylglucose-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (bis(tetrabenzylglucose)curcumin) (btbgc) and bis[4-tetraacetylglucose-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (bis(tetraacetylglucose)curcumin) (btagc) with vanadium in methanol, in a 2:1 molar ratio, which yield the co...

Cycloaddition of pyridine N-imine with 6-alkyl-4-oxohex-5-ynoates followed by condensation with hydrazine provides concise access to pharmacologically active 6-(pyrazolo[1,5-a]pyridin-3-yl)pyridazinones. For the first time alkynyl heterocycles are also shown to be effective dipolarophiles for pyridine N-imine, and analogous compounds can be accessed directly in modest yields through the reactio...

A facile and efficient one-pot synthesis of pyrrolidines and dispiro pyrrolidines/pyrrolizidines has been accomplished by the 1,3-dipolar cycloaddtion reaction of azomethine ylides generated insitu from paraformaldehyde/ninhydrin and secondary amino acids with electron-deficient dipolarophiles in good yield. The reaction proceeded with high regio and stereoselectivity. The products have been ch...

A facile synthesis of dispirooxindolopyrrolidines has been accomplished via a one-pot three component 1,3-dipolar cycloaddition reaction. The reaction of azomethine ylides generated in situ from L-phenylalanine and substituted isatins with a series of unusual (E)-2-oxoindolino-3-ylidene acetophenone dipolarophiles in the ionic liquid 1-butyl-3-methylimidazolium bromide [bmim]BF4, furnished the ...

1,3-Dipolar cycloaddition reactions provide convenient access to carbocyclic and heterocyclic five-membered ring systems. In some cases, 1,3-dipoles react with dipolarophiles without activation of either component. For example, the ozonolysis of olefins and the addition of nitrile oxides to alkynes often proceed without added promoters. With many substrate combinations, however, no cycloadduct ...

Based on polycyclic aromatic azomethine ylides (PAMYs), a metal-free "cycloaddition-planarization-sequence" is proposed, providing a unique entry to extended nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs). This method is highly versatile, as the structure of unprecedented N-PAHs can be tailored by the dipolarophile in the crucial 1,3-cycloaddition-reaction. Linear, as well as fiv...