1.3- Dipolar cycloaddition of benzonitrile oxide

Dipolar cycloaddition of benzonitrile oxide to 5-methoxy-6-methyl-6FM,4-diazepine results in a l,2,4-oxadiazolo[4,5-d][l,4]diazepine.189... 

The 1,3-dipolar cycloadditions of benzonitrile oxides with tertiary cinnamides yield the 5-phenyl and 4-phenyl regioisomers in a reversal of the expected regioselectiv-ities shown with methyl cinnamate. Calculations have shown that steric factors are responsible for this reversal of regioselectivity." The 1,3-dipolar cycloadditions of benzonitrile oxide with electron-rich and electron-poor dipolarophiles are accelerated by sodium dodecyl sulfate micelles. Phenyl nitrile ylides react with electron-deficient alkenes to produce five-membered -heterocycles where measured rate constants are between 4 x 10 and 7 x 10 lmoP ... 

Nitrile oxides react with the methyl enol ethers of (Rs)-l -fluoro-alkyl-2-(p-tolylsulfinyl)ethanones to produce (45,5/f,/fs)-4,5-dihydroisoxazoles with high regio-and diastereo-selectivity.87 In the 1,3-dipolar cycloaddition of benzonitrile oxide with adamantane-2-thiones and 2-methyleneadamantanes, the favoured approach is syn, as predicted by the Cieplak s transition-state hyperconjugation model.88 The 1,3-dipolar cycloaddition reaction of acetonitrile oxide with bicyclo[2.2.l]hepta-2,5-diene yields two 1 1 adducts and four of six possible 2 1 adducts.89 Moderate catalytic efficiency, ligand acceleration effect, and concentration effect have been observed in the magnesium ion-mediated 1,3-dipolar cycloadditions of stable mesitonitrile oxide to allylic alcohols.90 The cycloaddition reactions of acryloyl derivatives of the Rebek imide benzoxazole with nitrile oxides are very stereoselective but show reaction rates and regioselectivities comparable to simple achiral models.91. 

A series of oxadiazolo-2,3-benzodiazepines 27 were prepared because of their chemical similarity to known therapeutic 2,3-benzodiazepines <1995EPH411>. Their preparation was achieved by 1,3-dipolar cycloaddition of benzonitrile oxide, formed in situ from benzohydroxamoyl chloride, with 2,3-benzodiazepines 26 (Equation 2). 

There is also a known 1,3-dipolar cycloaddition of some nitrileamines 122 characterized by high yields at elevated temperatures in tetrahydofuran in the presence of triethylamine [113] (Scheme 4.39). Similar 1,3-dipolar cycloadditions of benzonitrile oxide 125 were studied in [114]. The reaction proceeds under mild conditions at room temperature in methylene chloride (Scheme 4.40). 

The chiral isoxazoline derivatives 490 were prepared in a highly enantioenriched form by 1,3-dipolar cycloaddition of benzonitrile oxide and pivalonitrile oxide with acrylate 489 (Equation 80) <2003SL1865>. 

Dipolar cycloaddition of benzonitrile oxide with 1 led to the formation of tetrahydrobenzoisoxazole 195 (74KGS901). Acyldimedone 183 with hydroxylamine afforded benzoisoxazole 196. Subsequent protecting group manipulation afforded the N-Fmoc 197 (04TL1237). 

Van Mersbergen D, Wijnen JW, Engberts JBFN (1998) 1,3-dipolar cycloadditions of benzonitrile oxide with various dipolarophiles in aqueous solutions. A kinetic study. J Org Chem 63 8801-8805... 

The second-order rate constant of 1,3-dipolar cycloadditions of benzonitrile oxide (85) with various dipolarophiles A-E were determined in water and organic solvents. The greatest accelerating effect was observed in water for the cycloaddition of 85 with electron-rich dipolarophiles A and B and in -hexane for the cycloadditions with electron-poor dipolarophiles C-E (Table 5.6). The results were explained in terms of frontier molecular orbital theory and enforced hydrophobic interactions. 

Engberts extended the systematic study of the effects of micelles on Diels-Alder reaction to 1,3-dipolar cycloadditions of benzonitrile oxide (85) with N-substituted maleimides (ethyl, -butyl, benzyl). The rate constants of these reactions in water and 1-propanol were only slightly different (kH2o/ki-propanoi = 1.2-1.7). When anionic SDS or... 

Table 5.6 Relative rate constants for 1,3-dipolar cycloadditions of benzonitrile oxide (85) with dipolarophiles A-E in various reaction media...

The 1,3-dipolar cycloadditions of benzonitrile oxide and C,N-diphenylnitrone to levoglucosenone were highly regio- and face-selective giving essentially the single products (81) and (82) respectively. ... 

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