Diazo transfer to in situ generated hydrazones using imidazosulfonyl azide as reagent results in the formation of 1,2,3-triazoles in good yields.

A general approach to new ligands embodying bis(oxazolinyl)pyridine has been developed, employing palladium-catalyzed Suzuki coupling and base-mediated cyclization as pivotal steps. A rhodium catalyst derived from the ligand 4-(4-ethylphenyl)-2,6-bis(4-isopropyl-4,5-dihydrooxazol-2-yl)pyridine gave excellent enantioselectivity in the asymmetric hydrosilylation of ketones. In addition the electronic effect of remote substituents on the catalytic activity of rhodium catalyst was studied.

The synthesis of novel dispiroheterocycles containing a bicyclo[2.2.1]heptane ring system through sequential [3+2] and [4+2] cycloadditions is described.

A highly regioselective synthesis of novel dispiroheterocycles by the cycloaddition of azomethine ylide generated through a decarboxylative route from sarcosine/proline/thiazolidine-4-carboxylic acid/1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid and ninhydrin with the dipolarophile 3-arylidene-4-chromanone is described.

The synthesis of novel polycyclic thiopyrano coumarin/chromone frameworks through intramolecular domino Knoevenagel hetero Diels–Alder reactions of 4-hydroxy coumarin and its benzo-analogous with S-prenylated aromatic aldehydes was studied. A high degree of chemoselectivity was achieved by the application of microwave irradiation and a solid support.

Synthesis of novel ferrocenyl oxindoles was successfully achieved, and a series of novel dispiroheterocyclic system has been synthesized by the cycloaddition of azomethine ylides generated by the decarboxylative route from secondary amino acids (sarcosine/proline) and isatin/acenaphthequinone/ninhydrin with the newly synthesized ferrocenyl oxindole. All of the cycloaddition reactions gave ferrocenyl substituted pyrrolidine/pyrrolizidine derivatives with very high regio and stereoselectivity in reasonable yiels.

In the title compound, C30H23NO4, the molecule includes two spiro junctions connecting acenaphthene rings and the pyrrolidine moiety. The acenaphthene ring atoms (C2, C7-C17) and (C3, C18-C28) make dihedral angles of 87.0(1) and 81.3(1)°, respectively, with the pyrrolidine ring system. The pyrrolidine ring exhibits an envelope conformation. In the crystal, packing is stabilized by C-H…π and π-π interactions.

A highly regio- and stereoselective synthesis of novel spiro pyrrolidines/pyrrolizidines containing β-lactam and oxazolone moieties under two different conditions is achieved using [3+2] cycloaddition methodology in moderate to good yield.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A series of novel N-methyl spiropyrrolidines have been synthesized in good yield by the cycloaddition reaction of azomethine ylides generated by a decarboxylative route from sarcosine and paraformaldehyde with conformationally locked s-trans enone functionality present in the (E)-3-arylidene-4-chromanone as dipolarophiles. The structure of the title compound was established by spectroscopic techniques.

The 1,3-dipolar cycloaddition of an azomethine ylide, generated from isatin and benzylamine by a 1,5-prototopic shift route with various p-substituted 2,6-bis(arylmethylidene)cyclohexanones under different conditions, proceeded regioselectively to give novel dispiroheterocycles. The product on subsequent annulation with hydrazine hydrate afforded 4-aryl-5-phenyl(spiro[2.3″]oxindole)3′-aryl-3′,3a′,4′,5′,6′,7′-hexahydro-2H-indazolospiro[7′.3]pyrrolidines in good yield.

In the title compound, C32H25NO3, the pyrrolidine ring and the five-membered ring of the indan moiety adopt twist and envelope conformations, respectively. The mol­ecules in the crystal structure are linked by an inter­molecular C—H⋯O hydrogen bond, forming chains running along the [\overline{1}01] direction.

In the title compound, C28H23NO4, the pyrrolidine ring adopts a twist conformation and the pyran ring in the chromanone system adopts a half-chair conformation. The mol­ecules associate via C—H⋯O inter­actions to form R22(18) dimers.

An assembly of polycyclic N-heterocycles, with the formation of four bonds and three rings, was obtained in good yield by the sequential intramolecular 1,3-dipolar cycloaddition via the N-metallation Ag(I)-catalysed imineroute and subsequent Pictet-Spengler cyclisation.

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. (C) 2004 Elsevier Ltd. All rights reserved.

In the title compound, C25H22N2O3S, the dihydropyran ring adopts a half-chair conformation and the dihydrothiapyran ring adopts a sofa conformation.

The cycloaddition reaction of non-stabilized azomethine ylides, generated through decarboxylation and deprotonation, with (E)-2-arylidene-1-tetralones as dipolarophile has been investigated. A high degree of regioselectivity has been observed in the synthesis of a new class of functionalised dispiroheterocyclic compounds bearing a tetralone, acenapthenequinone and oxindole framework.

Synthesis of dispiro 7-oxaindazolidines has been accomplished by regioselective 1,3-dipoiar cycloaddition reaction of azomethine ylide generated from secondary amine, morpholine, and isatin (via deprotonation route) with arylidene chromanones and arylidene tetralones as dipolarophiles.

In the title compound, C30H24N2O, the pyrrolidine ring adopts a twist conformation. The dihedral angle between the fluorene ring system and the phenyl ring is 68.3 (1)degrees. In the solid state, inversion-related molecules form dimers via N-H...O hydrogen bonds. Weak C-H...pi interactions also stabilize the molecular packing.

In the title compound, C29H26N2O3, the pyrrolidine ring adopts an envelope conformation and the cyclo­hexane ring adopts a chair conformation. The structure is stabilized by intramolecular C—H⋯O and π–π interactions.