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.     

Heterocycles from nitrile oxides. II . 1,2,4-oxadiazin-6-ones

Condensation of arylnitrile oxides with α-amino acid esters, other than those of glycine and analine, has been found to constitute a synthetic route to the hitherto unknown 1,2,4-oxadiazin-6-ones 7. α-Amino alcohols yield with nitrile oxides the corresponding acyclic N-(arylhydroxamoyl)amino alcohols, which are also accessible by borohydride reduction of compounds 7 . In contrast, the adducts formed from nitrile oxides and α-amino acids are unstable; they decompose readily into the aldehyde, derived from the amino acid, together with the aldoxime, derived from the nitrile oxide. Both decomposition products are also formed when compounds 7 are subjected to mild hydrolysis.     

Cycloaddition of benzoheteroazepine II Reactions and conformations of cycloadducts on1,5-benzothiazepines and 1,5-benzodiazepines with nitrile imine and nitrile oxides

Benzodiazepine and benzothiazepine derivatives have been well known as therapeutically important compounds. Four new tricyclic heterocyclic compounds, 3a,4,5,11-tetrahydro-3H-1,2,4-triazolo[4,3-d] [1, 5]benzothiazepines (3), 3a,4,5,11-tetrahydro-3H,6H-1,2,4-triazolo[4,3-d][1,5]benzodiazepine (4), 3a, 4,5,11-tetrahydro-1,2,4-oxadiazolo[4,5-d] [1,5]benzothiazepines (5, 6) and 3a,4,5,11-tetrahydro-6H-1, 2,4-oxadiazolo[4, 5-d] [ 1, 5 ] benzodiazepines (7,8), have been synthesized by 1,3-dipolar cycloaddition reactions of 2, 3-dihydro-1, 5-benzothiazepines and 2, 3-dihydro-1H-1, 5-benzodiazepine with benzonitrile N-phenylimine and benzonitrile oxides, respectively. The conformations of some cycloadducts and cycloaddition mechanism are described.     

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.     

1,3-Dipolar cycloaddition reactions of 1,3,4-oxadiazin-6-ones with nitrile oxides

2,5-Diaryl-1,3,4-oxadiazin-6-ones 1 gave with nitrile oxides 2 1,2,4-oxadiazole derivatives 4 . When mesitonitrile oxide 2a was used, bis-adducts 3 were also formed. The cycloadditions showed a remarkable site selectivity towards one carbon nitrogen double bond. The structure of both adducts was fully characterized by X-ray analysis.     

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.     

The reaction of 2-nitrosopyridine with nitrile oxides: First synthesis of 1,2,4-triazolo[1,5-a]pyridine 1,3-Di-N-oxides

Reactions of 2-nitrosopyridine with nitrile oxides afford either the novel title compounds or the corresponding 1,2,4-triazolo[1,5-a]pyridine 3-oxides.     

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.     

Reactions of nitrile oxides with nitrogen oxides. 1. Reactions with nitrogen tetroxide

We have studied the reaction of nitrile oxides with nitrogen tetroxide. It was shown that the reaction is selective: acetonitrile oxide yields ethylnitrolic acid, -oximinophenylacetonitrile oxide gives a mixture of isomers of phenylnitrofuroxan, and aromatic nitrile oxides give aryltrinitromethanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1620–1622, July, 1990.     

Efficient synthesis of 1,2,4-oxadiazine-5-ones via [3+3] cycloaddition of in situ generated aza-oxyallylic cations with nitrile oxides

1,2,4-Oxadiazin-5-ones were prepared via [3+3] cycloaddition of in situ generated aza-oxyallylic cations with nitrile oxides in good yields and excellent functional group compatibility. This efficient transformation is metal-free and is promoted by an inorganic base Cs₂CO₃. In addition, this reaction features simple-operation, mild conditions, and high regioselectivity.     

Cycloaddition reactions of 2,3-dihydro-1H-1,4-diazepines with nitrile oxides and imines. Synthesis of bis[1,2,4]oxadiazolo-and bis[1,2,4]triazolo[1,4]diazepine derivatives

New heterotricyclic systems, 6,10a,11,11a-tetrahydro-5H-bis[1,2,4]oxadiazolo[4,5-d:5′,4′-g][1,4]diazepines 6,7,9-11 and 5,6,10,10a,11,11a-hexahydro-1H-bis[1,2,4]triazolo[4,3-d:3′,4′-g][1,4]diazepines 8,12 have been obtained by double site- and regie-specific 1,3-dipolar cycloaddition of mesitylnitrile oxide ( 1 ) or diphenylnitrile imine ( 2 ) to 5,7-disubstituted 2,3-dihydro-1H-1,4-diazepines 3-5. The structure of the synthesized bis-adducts 6-12 shows that the hetero double bonds are much more reactive than the olefinic ones in the dipolarophiles under study. No evidence for the formation of mono-adducts was obtained.     

Phosphorylinitrile oxides. 7. Quantum chemical study of the dimerization of nitrile oxides

A semiempirical MNDO calculation was carried out for the singlet potential energy surface for the dimerization of acetonitrile oxide leading to dimethylfuroxane. The dimerization of nitrile oxides proceeds by a two-step mechanism. The rate-limiting step is formation of a dinitrosoethylene intermediate. A semiempirical AMI calculation was carried out to study the effect of phosphoryl substituents on formation of the transition state of the rate-limiting step in the dimerization of dimethoxyphosphorylnitrile oxide. Independently of the initial orientation of the two phosphorylnitrile oxide molecules, a gauche-oriented dimerica species is formed in the first step in the dimerization. There is hardly any specific effect ofthe phosphoryl substituents in the first step of phosphorylnitrile oxide dimerization.Communication 6, see ref. [1].Kazan State Technological University, 420015 Kazan, and Institute of Physiologically Active Compounds, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1269–1273, September, 1994. Original article submitted August 5, 1994.     

A Route to 1,2,4-oxadiazoles and their complexes via platinum-mediated 1,3-dipolar cycloaddition of nitrile oxides to organonitriles

A significant activation of the Ctbd1;N group in organonitriles upon their coordination to a platinum(IV) center has been found in the reaction of [PtCl(4)(RCN)(2)] (R = Me, Et, CH(2)Ph) with the nitrile oxides 2,4,6-R'(3)C(6)H(2)CNO (R' = Me, OMe) to give the (1,2,4-oxadiazole)platinum(IV) complexes (R = Me, R' = Me (1); R = Et, R' = Me (2); R = Et, R' = OMe (3); R = CH(2)Ph, R' = Me (4)); the [2 + 3] cycloaddition was performed under mild conditions (unless poor solubility of [PtCl(4)(RCN)(2)] precludes the reaction) starting even from complexed acetonitrile and propionitrile, which exhibit low reactivity in the free state. The reaction between complexes 2-4 and 1 equiv of Ph(3)P=CHCO(2)Me in CH(2)Cl(2) leads to the appropriate platinum(II) complexes (5-7); the reduction failed only in the case of 1 insofar as this complex is insoluble in the most common organic solvents. All the platinum compounds were characterized by elemental analyses, FAB mass spectrometry, and IR and (1)H, (13)C((1)H), and (195)Pt NMR spectroscopies, and three of them also by X-ray crystallography. The oxadiazoles formed in the course of the metal-mediated reaction were liberated almost quantitatively from their Pt(IV) complexes by reaction of the latter (complexes 2-4) with an excess of pyridine in chloroform, giving free 1,2,4-oxadiazoles and trans-[PtCl(4)(pyridine)(2)]; the sequence of the Pt(IV)-mediated [2 + 3] cycloaddition and the liberation opens up an alternative route for the preparation of this important class of heterocycles.     

Reactions of nitrile oxides with nitrogen oxides. 2. Reactions with nitrogen monoxide and nitrogen sesquioxide

We have studied the reactions of aromatic nitrile oxides with nitrogen monoxide and nitrogen sesquioxide. It was shown that nitrogen monoxide removes an oxygen atom from the nitrile oxide with formation of the corresponding nitrile and nitrogen dioxide. The reaction products with nitrogen sesquioxide are formed as a result of reactions of the nitrile oxide with nitrogen monoxide and nitrogen tetroxide.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1623–1625, July, 1990.     

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...     

Heterocyclic synthesis using nitrile imines. 6. Synthesis of some new substituted 4,5-dihydro-1H-1,2,4-triazoles

A new series of substituted 1,2,4-triazoles was synthesized from the cycloaddition reaction of alkanal and cycloalkanal hydrazones containing electron-withdrawing groups (MeCO, PhCO, and MeOCO) with appropriate hydrazonoyl halides. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 392–398, March, 2007.     

Chemical properties of N'-cyanodiazene N-oxides. Reactions involving the nitrile group

The reactivity of the nitrile group in N'-cyanodiazene N-oxides has been examined for the first time. A general approach to the synthesis of nitrogenous functional derivatives of azoxycarboxylic acids by reaction of N'-cyanodiazene N-oxides with nucleophiles (water, alcohol, and hydroxylamine) is described. A method of synthesis of novel azoxy-1,2,4-oxadiazoles and tetrazoles has been developed in which aliphatic, aromatic, or heterocyclic N'-cyanodiazene N-oxides are reacted with benzonitrile N-oxide or sodium azide. Trimerization of N-cyanodiazene N-oxides, catalyzed by anhydrous HCl, has given novel symm-triazines in which the heterocycle bears three diazene N-oxide groups.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1647–1653, July, 1991.     

Synthesis of fused ring 1,2,4-triazoles by intramolecular cycloaddition of nitrile imines to the nitrile function

Treatment of 1-chlorohydrazones (IIa-c) with triethylamine gave fused ring 1,2,4-triazoles arising from an intramolecular cycloaddition of the intermediate nitrile imines (IIIa-c). This reaction was not observed in the case of one compound (IId) bearing an unactivated nitrile group.     

Tetraacetylethylene and nitrile oxides: Synthesis of spirofuranisoxazoles

trans and cis-3-Hexen-2,5-dione, 2 , reacted with nitrile oxides to give 4,5-dihydroisoxazoles 3a-c with the trans configuration. On the contrary the reaction between 3,4-diacetyl-3-hexen-2,5-dione, 1 , with nitrile oxides yielded 3-aryl-8,9-diacetyl-7-hydroxy-7-methyl-1,6-dioxa-2-azaspiro[4.4]nona-3,8-dienes 9a-e. The reaction is completely regiospecific. The cycloadducts show ring-open chain tautomerism.