Nitnle oxides

The regio- and stereoselectivities of cycloadditions of trifluoroacetonitrile oxide, which is generated m situ by treatment of the tnfluoroacetohydroxamyl bromide etherate with tnethylamine in toluene (equation 31), have been determined in a senes of studies by Tanaka [55, 36, 37, 5 ]. The highly reactive nitnle oxide reacts regioselectively with a variety of activated terminal alkenes and alkynes (equations 32 and 33)... 

In a manner analogous to classic nitrile iinines, the additions of trifluoro-methylacetonitrile phenylimine occur regiospecifically with activated terminal alkenes but less selectively with alkynes [39], The nitnle imine reacts with both dimethyl fumarate and dimethyl maleate m moderate yields to give exclusively the trans product, presumably via epimenzation of the labile H at position 4 [40] (equation 42) The nitrile imine exhibits exo selectivities in its reactions with norbornene and norbornadiene, which are similar to those seen for the nitrile oxide [37], and even greater reactivity with enolates than that of the nitnle oxide [38, 41], Reactions of trifluoroacetomtrile phenyl imine with isocyanates, isothiocyanates, and carbodiimides are also reported [42]... 

Likewise, trifluoromethyl-substituted nitrile imines [172] and nitnle oxides [173,174, 7 75] have been used to synthesize tnfluoromethyl substituted five-membered ring systems of the pyrazole, isomzole, isoxazohne, and 1,2,4-oxadiazole... 

Synthesis of thiopheno[3,4-c isoxa2olide is shown in Eq. 4.4, in which the Michael addidon of allyl thiol to fi-nitro enones and subsequent nitnle oxide cyclizadon are involved. ... 

The 1,4-dclclitiQn of RMgX or RLi to nitroalkenes produces nitrondte inrermedidtes, which dre converted into nitrodlkdnes, nitnle oxides Coxime chloridesi, or cdrboxylic dcids, depending on the conditions of hydrolysis fScheme 4 14 ... 

The reacdon of nitroalkenes or nitroalkanes v/ithTCH and Me-SiN-, gives ct-azido fiincdon-alized hydroxamoyl chlciides, which act as precursors of nitnle oxides fEq. 6.34. " ... 

A new route to nitnle oxides based on the reacdon of primary alkyl bromides v/ith NaNOj n the presence of acedc acid, is also reported fEq. 6.35. This reacdon is used for the direct... 

RecenQy, diastereoselecdve synthesis of highly subsdnited 2,5-diaminohexanes via nitnle oxide cycloaddidon to an opdcally acdve vinylogous amino acid has been shown. 

Sever il strategies have been proposed to imptove the regioselecdvity of nitnle oxide cycloaddidon. Kanemasa and coworkers have reported high-rate acceleradon and regioselecdvity in nitnle oxide cycloaddidons to the magnesium ilkoxides of illylic and horao illylic ilcohols fEq. 8.64. ... 

Isoxazolmes are good preciusors of a,fi-unsatiuated ketones.This transformadon ii nsefid for synthesis of polyenes. For example, nitnle oxide cycloaddidon chemistry is used tc prepare4-oxo-2-alkenylphosphonates, which are useful to synthesize a long polyethylenic unii via Woodworth-Errunons olefinadon fEq. 8.66. ... 

As d new utility of nitnle oxide in organic synthesis, synthesis of medium and large rings by intramolecular nimle oxide dimerization is reported fEq 8 67 ... 

Eglichi and Ohno have used silyl nitroaate induced 1,3-dipolar cycloaddidon For functionalization of fuilerene fEq. S.76. " Nitnle oxides also undergo 1,3-dipolar cycloaddidon... 

Recently, solicon-tethered thastereoselecdve ISOC reactions have been reported, in which effective control of remote acyclic asymmetry can be achieved fEq 8 91) Whereas ISOC occur stereoselecdvely, INOC proceeds v/ith significandy lower levels of diastereoselecdon The reaction pathways presented in Scheme 8 28 suggest a plausible hypothesis for the observed difference of stereocontrol The enhanced selecdvity in reacdons of silyl nitronates may be due to l,3- illylic strain The near-linear geometry of nitnle oxides precludes such differendadng elements fScheme 8 28 ... 

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