Polyfluorinated nitrile oxides

(2+3)-Cycloaddition of polyfluorinated aliphatic nitrile oxides, generated in situ, to donor dipolarophiles takes place regioselectively to give the 5-substituted isoxazolines, and is limited by the donor and steric properties of the dipolarophiles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, 663–667, May, 1989.     

Synthesis and properties of stable aromatic bis(nitrile oxides)

A number of stable bis(nitrile oxides) based on dimesitylmethane and didurylmethane and their analogs in which two aromatic rings are joined by various bridging groups were synthesized. The thermal isomerization of the bis(nitrile oxides) to diisocyanates and the relative reactivities of the bis(nitrile oxides) in 1,3-dipolar cycloaddition to styrene were studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1398–1403, June, 1991.     

Synthesis of stable functionally substituted nitrile oxides of the aromatic series

Stable functionally substituted mononitrile oxides were obtained from the previously obtained sterically hindered aldehydes of the mesitylene series. The previously unknown bisnitrile oxide was also synthesized from triethyl-benzene; the compound is an effective crosslinking agent. The synthesis was carried out via the stage of oximation and oxidation of the oxime by sodium hypochlorite.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1201–1203, May, 1991.     

Syntheses based on nitrile oxides. 1. Reaction of aromatic nitrile oxides with N-cyanimides

The reaction of trialkylaminocyanimides with aromatic nitrile oxides leads to trialkylamino-(3-aryl-1,2,4-oxadiazol-5-yl)imides, while the corresponding reactions with sulfylcyanimines and phosphincyanimides do not take place. Using x-ray structural analysis the principal structural features of the 1,2,4-oxadiazole products have been elucidated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2084–2089, September, 1990.     

Syntheses based on nitrile oxides

Interaction of aromatic nitrile oxides with bis-trimethylsilylthiodiimide results in 2-amino-4-aryl-1,2,3,5-oxathiadiazoles, the first representatives of a new class of heterocyclic compounds.For Part 2, see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 742–743, April, 1993.     

Synthesis of pyranosyl amidoximes by addition of amines to pyranosyl nitrile oxides

Addition of amines to pyranosyl nitrile oxides, generated by base-induced dehydrochlorination of the corresponding hydroximoyl chloride, affords pyranosyl N-alkyl/aryl-formamide oximes (41-90%). Reaction with amino acid esters yields the corresponding amidoximes and/or 3-pyranosyl-1,2,4-oxadiazin-6-ones. The structure of N-phenyl-C-(2,3,4-tri-O-acetyl-β-D-xylopyranosyl)formamide oxime was established by X-ray crystallography.     

Synthesis of isoxazoles by hypervalent iodine-induced cycloaddition of nitrile oxides to alkynes

Treatment of oximes with hypervalent iodine leads to substituted isoxazoles via rapid formation of nitrile oxides. Reaction with terminal alkynes led to a series of 3,5-disubstituted isoxazoles with complete regioselectivity and high yield, in a procedure mild enough to prepare a range of nucleoside and peptide conjugates. Exceptionally high reaction rates were found for the formation of 3,4,5-trisubstituted isoxazoles from a cyclic alkyne.     

Stereoconvergent and stepwise 1,3-dipolar cycloadditions of nitrile oxides and nitrile imines

The first example of stereoconvergent 1,3-dipolar cycloaddition of nitrile oxides and nitrile imines with E/Z isomeric mixture of electron-deficient olefins is reported, delivering isoxazolines and pyrazolines bearing two vicinal stereogenic tertiary and trifluoromethylated quaternary carbon centers with perfect regioand diastereoselectivities. The possibility of concerted cycloaddition/epimerization sequence under basic condition to form the thermodynamically stable diastereomers is excluded th...     

Cycloaddition of benzynes and nitrile oxides: synthesis of benzisoxazoles

A mild and efficient process has been developed for the synthesis of benzisoxazoles through the cycloaddition of benzynes and nitrile oxides. This method allows access to both (hetero)aromatic and alkenyl-substituted benzisoxazoles. Preliminary studies concerning regioselectivity are also reported.     

Syntheses with nitrile oxides. 2. Reaction of aromatic nitrile oxides with bis(trimethylsilylcarbodiimide)

The reaction of aromatic nitrile oxides with bis(trimethylsilylcarbodiimide) gives 5-amino-3-aryl-1,2,4-oxadiazoles.For previous communication, see [1].N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117334 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2430–2432, October, 1992.     

Cycloaddition of nitrile oxides to substituted vinylphosphonates

Cycloaddition of nitrile oxides to substituted vinylphosphonates was performed. A series of 4,5‐dihydroisoxazoles containing phosphonyl group were synthesized under very mild condition in excellent regiospecificity. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:309–311, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10149     

Synthesis of tetrachloroisophthalic and-terephthalic aldehydes and stable bis(nitrile oxides) based on them

A new route for the synthesis of 2,4,5,6-tetrachloroisophthalic and 2,3,5,6-tetrachloroterephthalic aldehydes from the corresponding tetrachlorobenzenes was developed. The method involves dichloromethylation of the initial compounds with chloroform in the presence of aluminum chloride and subsequent hydrolysis of the resulting 1,3-bis(dichloromethyl)-2,4,5,6-tetrachlorobenzene and 1,4-bis(dichloromethyl)-2,3,5,6-tetrachlorobenzene. Stable 2,4,5,6-tetrachlorobenzene-1,3-dicarbonitrile oxide and 2,3,5,6-tetrachlorobenzene-1,4-dicarbonitrile oxide were obtained for the first time from the above aldehydesvia the corresponding oximes. The products were characterized by IR and¹³C NMR spectra, and were converted into substituted 1,3- and 1,4-phenylenebis(isoxazolines) using 1,3-dipolar cycloaddition with styrene. Translated fromIzvestiya Akademit Nauk. Seriya Khimicheskaya, No. 1, pp. 106–109, January. 1997.     

Optically active nitrile oxides: synthesis and 1,3-dipolar cycloaddition reactions

Baker’s yeast-promoted reduction of the CC bond in 2-aryl-1-nitropropenes gave the corresponding optically active (R)-2-aryl-1-nitropropanes of high enantiomeric purity (ee >90%). They were next converted with the aid of the Mukaiyama and Hoshino method into the optically active nitrile oxides, which were made to react in situ with ethyl propiolate, methylvinyl ketone and (R)-1-phenyl-2-(phenylsulfonyl)ethyl acrylate to yield the appropriate, enantiomerically enriched, isoxazoles or 4,5-dihydroisoxazoles as diastereomeric mixtures, respectively.     

Huisgen reaction of nitrile oxides and nitrile imines leading to isoxazoline and pyrazole-4,6-diones

Huisgen reaction of nitrile oxides and nitrile imines generated in situ in the presence of N-benzylmaleimide afforded regiospecifically the corresponding cis-3-aryl-5-benzyl-3a,4,6,6atetrahydro-4H, 6H-pyrrolo[3,4-d]isoxazoline-4,6-diones and cis-3-aryl-5-benzyl-1-(2′,4′-dibromophenyl)-3a, 4,6,6a-tetrahydro-1H,5H-pyrrolo[3,4-c]pyrazole-4,6-diones in good yield. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 935–939, June, 2006.     

1,3-Dipolar cycloaddition reactions of nitrile oxides and nitrile imines with 2-methoxyvinyl phenyl ketone

Nitrile oxides react regioselectively with 2-methoxyvinyl phenyl ketone 1 to give 4-benzoylisoxazoles 4 via elimination of methanol from the primary cycloadducts 3 . After heating with an excess of nitrile oxide bis-cycloadducts 5 were also formed. Reactions of nitrile imines with 1 are less regioselective yielding both 4-benzoylpyrazoles 9 and 5-benzoytpyrazoles 10 , whereas no bis-cycloadducts were isolated.     

Reaction of some aromatic nitrile oxides with dimedone

1,3-Dipolar cycloaddition of benzonitrile and m-nitrobenzonitrile oxides to the enol form of dimedone gives the corresponding 4-oxotetrahydrobenzisoxazoles. A second reaction path — nucleophilic addition of the enol to the N-oxide to give a hydroxamic acid derivative — is observed in the case of m-nitrobenzonitrile oxide. The tetrahydrobenzisoxazoles are converted to enamine derivatives of benzoyldimedone under catalytic hydrogenation conditions.     

Intramolecular 1,3-dipolar cycloadditions of aliphatic nitrile oxides

Treatment of functionalized 1-chloro-oximes ( 3c and 4a,b ) with triethylamine originates nitrile oxides ( 1c and 2a,b ) which undergo an intramolecular cycloaddition providing fused-ring isoxazole derivatives ( 7c and 8a,b ). The latter reaction was not observed for one substrate ( 2c ).