Formonitrile oxide

In contrast to other furoxans, the cycloreversion of 3,4-dinitrofuroxan to nitro-formonitrile oxide was observed even at room temperature. The nitrile oxide could be trapped in situ with electron-deficient nitriles (Scheme 149) (95MC231). Attempts to obtain cyclo adducts with styrene, phenylacetylene, rran.s-stilbene, and cyclohexene failed. 

Thus, (dimorpholinophosphoryl)formonitrile oxide undergoes 1,3-addition reactions with HC1, HI, primary and secondary amines, acylhydrazines, and even with thiourea or thiosemicarbazide (Scheme 1.13) (98). The former gives (dimor-pholinophosphoryl)isothiocyanate and urea. Those products might arise from a retro destruction of the unstable 1,3,5-oxathiazoline. The latter transforms to the isothiocyanate, the product of addition of a second molecule of thiosemicarbazide. (98). 

Related (diisopropoxyphosphoryl)- and (diisobutoxyphosphoryl)formonitrile oxides (114), generated in basic media from the corresponding oximes react in situ with alcohols, phenols, alkanethiols, thiophenols, aliphatic and aromatic primary amines, hydrazines and hydrazides as well as 4-aminoantipyryne to give hydroxymates, thiohydroxymates, and amidoximes, respectively. It is important to note that the addition is stereoselective and gives E-adducts with the exception of (i-Pr0)2P(0)C( N0H)0Me, which is formed as a 1 1 mixture of E and Z isomers. 

Facial selectivity in 1,3-dipolar cycloadditions to cis-3,4-dimethylcyclobutene (73) (Scheme 1.21) was studied. Only phenylglyoxylo- and pyruvonitrile oxides lacked facial selectivities (anti syn = 1 1). All other nitrile oxides formed preferably anti-74. The anti/syn ratio increased from 60 40 (R = P-O2NC6K4) and 65 35 (R = Ph) to 87 13 and 92 8 for bulky ten-Bu and mesityl substituents, respectively. The transition-state structure of the cycloaddition of formonitrile oxide was determined using both HF/6-31G and B3LYP/6-31G methods. The... 

A study of the regioselectivity of the 1,3-dipolar cycloaddition of aliphatic nitrile oxides with cinnamic acid esters has been published. AMI MO studies on the gas-phase 1,3-dipolar cycloaddition of 1,2,4-triazepine and formonitrile oxide show that the mechanism leading to the most stable adduct is concerted. An ab initio study of the regiochemistry of 1,3-dipolar cycloadditions of diazomethane and formonitrile oxide with ethene, propene, and methyl vinyl ether has been presented. The 1,3-dipolar cycloaddition of mesitonitrile oxide with 4,7-phenanthroline yields both mono-and bis-adducts. Alkynyl(phenyl)iodonium triflates undergo 2 - - 3-cycloaddition with ethyl diazoacetate, Ai-f-butyl-a-phenyl nitrone and f-butyl nitrile oxide to produce substituted pyrroles, dihydroisoxazoles, and isoxazoles respectively." 2/3-Vinyl-franwoctahydro-l,3-benzoxazine (43) undergoes 1,3-dipolar cycloaddition with nitrile oxides with high diastereoselectivity (90% de) (Scheme IS)." " ... 

The chemistry of nitrile oxides, in particular their application in organic synthesis, has been continuously developed over the past two decades and represents the main theme of this chapter. The parent compound, fulminic acid (formonitrile oxide), has been known for two centuries, and many derivatives of this dipole have been prepared since that time. Several simple and convenient methods for the preparation of nitrile oxides have evolved over the years. Dehydrochlorination of hydroximoyl chlorides was first introduced by Werner and Buss in 1894 (1). A convenient synthesis of isoxazoles was reported by Quilico et al. (2 ), and then the discovery of nitrile oxide cycloadditions to alkenes was subsequently noted by the same group (5). 

The last results reported in this field are related to the 1,3-dipolar reactions of tert-butyl ( )-4,4-diethoxy-2-p-tolylsulfinylbut-2-enoate and (S5,Ss) and (R5,Ss) 5-ethoxy-3-p-tolylsulfinylfuranones (42a and 42b) with different nitrile oxides [ 167]. Acyclic sulfoxides react with benzonitrile, acetonitrile, and bromo-formonitrile oxides to yield isoxazoles resulting in desulfinylation from the adducts. Cyclic dipolarophiles afford bicyclic isoxazolines in their reactions with benzonitrile oxide. The reactivity of the double bond as a dipolarophile is strongly increased by the sulfinyl group. The regioselectivity of these reactions... 

As shown in Equation (10), the 1,3-dipolar cycloaddition of in situ generated carboethoxy-formonitrile oxide to a dihydropyran has been used to construct the terminal isoxazoline ring of the tricyclic heterocycle (30) <86T1407>. The [k4s + 7t2s] pericyclic product is obtained as a 70/30 inseparable mixture of diastereomers in 50% yield. 

Exposure of ethylene to an ethereal solution of formonitrile oxide gave the unstable 3-anti- aldoximino-2-oxazoline which was converted into the syn-oxime by ethanolic hydrogen chloride. The syn-oxime undergoes base-catalyzed cyclization to give A3-isoxazolidino[2,3-h][l,2,5]oxadiazoline (equation 32) (74JHC63). 

The addition of (ethoxycarbonyl)formonitrile oxide to (-i-)-(S)-isopropylidene-3-butene-1,2-diol led to an 80 20 mixture (60% diastereomeiic excess) of diastereomers in ca. 70% yield (Scheme 21) the major... 

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