An efficient synthesis of pyrazoles from tosylhydrazones and nitroalkenes was developed. In comparison with the previously reported 1,3-dipolar cycloaddition reaction of diazo compounds with electron-deficient alkenes or alkynes, this methodology proceeded with a sequential Baylis-Hillman/intramolecular cyclization mechanism and a variety of reversed regioselectivity products were prepared in g...

The construction of multivalent structures such as sugar heterodimers, glycoclusters, calix sugars, multicalixarenes, and glycocyclodextrins is designed by using 1,3-dipolar cycloaddition as a versatile and efficient tool which allows the creation of heterocyclic bridges between the different units that are coupled.

Truncated phosphonated C-1'-branched N,O-nucleosides have been synthesized in good yields by 1,3-dipolar cycloaddition methodology, starting from N-methyl-C-(diethoxyphosphoryl)nitrone 7. Preliminary biological assays show that β-anomers are able to inhibit HIV in vitro infection at concentrations in the micromolar range. Higher SI values with respect to AZT indicated that the compounds were en...

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...

An efficient protocol for the synthesis of a range of 1,2-benzisoxazoles using an improved 1,3-dipolar cycloaddition of nitrile oxides and benzyne is described. Key to the procedure is the in situ generation of the reactive nitrile oxide and benzyne reactants simultaneously.

The synthesis of unnatural pyrrolizidines has been studied using a multicomponent-domino process involving proline or 4-hydroxyproline esters, an aldehyde and a dipolarophile. The formation of the iminium salt promotes the 1,3-dipolar cycloaddition affording highly substituted pyrrolizidines under mild conditions and high regio- and diastereoselectivities.

A new strategy for the construction of optically active 5'-CF3 spiro[pyrrolidin-3,2'-oxindole] was described. A series of unprecedented 1,3-dipoles were obtained by condensation of CF3CH2NH2 with isatins. The 1,3-dipolar cycloaddition reactions of these ketimines with enals gave the products bearing four contiguous stereogenic centers in excellent yields, diastereoselectivities and enantioselec...

The first chiral phosphoric acid catalyzed highly diastereo- and enantioselective 1,3-dipolar cycloaddition reaction of azlactones and methyleneindolinones was disclosed. By using a BINOL-derived chiral phosphoric acid as the catalyst, azlactones were activated as chiral anti N-protonated 1,3-dipoles to react with methyleneindolinones to yield biologically important 3,3'-pyrrolidonyl spirooxind...

A four-folded azidation of tetrakis(4-iodophenyl)methane and -adamantane leads to stable organic azides, but yet energetic materials, measured by differential scanning calorimetry (DSC). The rigid and symmetrical structures can be useful for new polymer and nanomaterial developments in material sciences as well as bioconjugations, after 1,3-dipolar cycloaddition reactions with terminal alkynes ...

[reaction: see text] Several water-soluble calix[4]arenes were synthesized via Huisgen 1,3-dipolar cycloaddition between azides and alkynes. Cationic, anionic, and nonionic calixarenes were prepared from a common azidocalixarene intermediate. Azidocalixarenes performed better than alkynylcalixarenes as precursors. The aggregation behavior of the water-soluble calixarenes was studied by (1)H NMR...