Nitrile oxide addition

Isoxazolin-5-imines were produced by nitrile oxide addition to cyanoacetates (62HC(17)l,p.7), by the reaction of nitrones with phenylacetonitrile (74CB13), and by base addition of nitrosobenzene to nitriles (Scheme 148) (72LA(762)154). 

The use of chiral dipolarophiles, such as the nitrile oxide additions to chiral furanones, have received much interest. The cycloaddition of various 1,3-dipolar reagents to the enantiomeric ally pure furanones 170 and 227 showed excellent diastereofacial control by the menthyloxy substituent, especially in nitrone and nitrile oxide additions (cf. Table II) (88TL5317). 

Selective nitrile oxide addition at the internal C(4)=Ca double bond, to give the spiro compound, is described for 4-vinylideneoxazolidin-2-one (228). 

Dipolar cycloaddition of 4-arylmethyleneisoxazol-5-ones 794 and 2-methyl-4-phenyl-5(4//)-oxazolone 795 leads to pyrrole-3-carboxyhc acids that have been isolated as hydroxamates 796. The authors carried out this cycloaddition-nitrile oxide addition as a one-pot reaction (Scheme 7.243). ... 

There have also heen a few reports of 1,3-dipolar cycloaddition to dioxolane-containing dipolarophiles. The regioselectivity of nitrile oxide addition to give products 155 and 156 has been examined, in some cases using ultrasound <1995JCCS877, 1995JOC7701>, and the stereochemistry of mesitonitrile oxide addition to compounds... 

In this sequence, a nitrile oxide addition to an enol ether then elimination formed the isoxazole. Ring cleavage of the isoxazole accompanying decarboxylation, showed how the heterocycle can serve as a synthon for an a-cyano aldehyde. 

Intramolecular nitrile oxide addition to the 2,3-double bond of thiophene has been used to synthesize several spiro-annulated heterocycles <88S342>. 

Nitrile oxide addition and reduction then gives the ketone... 

Cyclitols have been used as chiral auxiliaries for nitrile oxide additions to acrylates,and chiral azomethine ylides, for example 130 and 131, have been used for the asymmetric synthesis of pyrrolidines ylide generation involves treatment of a tertiary amine N-oxide with LDA. ... 

The introduction of a bromo atom into the a-position of an unsaturated ketone or carbonyl group, in general, inverts the nitrile oxide addition completely, and a Michael addition to the activated double bond of aUene 355 directs the subsequent cycloaddition into the p,y-double bond generating adduct 358, which cannot be obtained from 355 directly [125aj. 

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