The dipolar cycloaddition reactivity of N-(1-naphthy1)-1,4- benzoquinoneimine N-oxide and N-phenyl-1,4- naphthoquinoneimine Noxide are investigated, The latter gives the expected adducts with common dipolarophiles such as acrylonitryle, methyl methacrylate, dimethylacetylene dicarboxylate and N-phenylmaleimide. The reactivity of the former nitrone is found to be minimal. It undergoes, how...

In a reaction that proceeds under mild conditions with remarkable functional group tolerance, structurally diverse 3-amino-2-cyclopentenones bearing a quaternary carbon at the 4-position have been synthesized through a formal [3+2]-cycloaddition reaction of silylated ketene imines (SKIs) and enoldiazoaceates by dirhodium catalysis.

Isoxazoline analogues of artemisinin were obtained in low yield and low diastereoselectivity from the 1,3-dipolar cycloaddition of nitrile oxides. Alternatively, starting from the aldehyde 7, a number of transformations--Wittig reaction and reduction, Henry reaction and cyanohydrin formation--were achieved in significantly higher yields. In the cases where a new stereocenter was introduced this...

Hydrazones and oximes are widely useful structures for conjugate formation in chemistry and biology, but their formation can be slow at neutral pH. Kinetics studies were performed for a range of structurally varied hydrazines, and a surprisingly large variation in reaction rate was observed. Structures that undergo especially rapid reactions were identified, enabling reaction rates that rival o...

The copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction was applied as the novel method of DNA immobilization on a modified solid support. The CuAAC click reaction enables the covalent binding of DNA modified with pentynyl groups at its 5'-end to azide-loaded slides. Click microarrays were produced using this approach and successfully employed in biological/model experiments.

The Lewis acid-mediated reactions of allene-ene compounds, derived from 3-methylcitronellal or dimethyl malonate, were carried out using various Lewis acids such as ethylaluminum dichloride, diethylaluminum chloride, titanium chloride, zinc chloride etherate, or boron trifluoride etherate, affording unexpectedly intramolecular [2+2]cycloaddition products under some particular reaction condition...

The catalytic, enantioselective, [4 + 2] cycloaddition reaction of ortho-quinone methides with silyl ketene acetals is described. This mechanistically interesting reaction, initiated by a chiral cinchona alkaloid-derived ammonium fluoride "precatalyst" complex, affords a variety of alkyl- and aryl-substituted 3,4-dihydrocoumarin products in excellent yield and with good enantioselectivity.

[(Salcen)Cr(III) + Lewis base] was found to be a highly active and selective catalyst system in the [2+3] cycloaddition between epoxides and isocyanates to form 5-oxazolidinones. The reaction proceeds to high yield under mild reaction conditions and is applicable to a variety of terminal epoxides and aryl isocyanates.

A Diels-Alder reaction between cyclopentadiene and a variety of ketenimines is reported. A copper(I)-bis(phosphine complex catalyzes the cycloaddition across the C═N bond of the ketenimine in a [4 + 2] reaction to give an enamine intermediate that is hydrolyzed upon purification to generate aminoketones.