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Hydrazones alkenes

Hydroperoxides have been obtained from the autoxidation of alkanes, aralkanes, alkenes, ketones, enols, hydrazones, aromatic amines, amides, ethers, acetals, alcohols, and organomineral compounds, eg, Grignard reagents (10,45). In autoxidations involving hydrazones, double-bond migration occurs with the formation of hydroperoxy—azo compounds via free-radical chain processes (10,59) (eq. 20). [Pg.105]

Monosubstituted hydrazones react with alkenes and alkynic compounds to yield pyrazolidines and pyrazolines, respectively (71LA(743)50, 79JOC218). Oxidation often occurs during the reaction and pyrazoles are isolated as the end product. [Pg.284]

MMPP-6H20 (magnesium monoperoxyphthalate), pH 7 buffer, MeOH, 0°, 5-120 min, 76-99% yield. These conditions were used to cleave the related SAMP hydrazone in the presence of two trisubstitued alkenes in 46% yield. ... [Pg.351]

A -l,3,4-Telluradiazolines 79 were obtained by coupling crowded hydrazones with TeCl2 in the presence of triethylamine (93CL1047 98MI1). Thus, tellura-diazoline 79a was prepared in 26% yield based on the hydrazone of 1,1,3,3-tetramethylindanone. The byproducts of this reaction are azine 80, alkenes 81 and 82, and 1,1,3,3-tetramethylindanone. [Pg.28]

Reduction, carboxyl groups, 56,83 Reduction of a,0-unsaturated p-toluene-sulfonyl-hydrazones to alkenes, 59,42 Reductive alkylation, 56,52 Reductive cleavage, 56, 101 Resolution of amines, 55,80, 83 Rexyn 201,55,4 Rhodium(III) oxide, 57, 1 Ring contraction, 56, 107 Ring expansion of cycloalkanones to cycloalkenones, 59, 113... [Pg.121]

In general, nitrilimines are generated in the presence of a suitable dipo-larophile. Thus, heating an equimolar mixture of hydrazone 313, alkene 314, and chloramine-T trihydrate in ethanol under reflux for 3 h provided pyrazolines 315 in 68-90% yield [81]. The cycloaddition in all the cases was regiospecific as indicated by NMR (Table 23). [Pg.44]

Isoxazolidinoindolizines and pyrazolidinoindolizines, 268, can be prepared from the oximes or hydrazones 267. 1,3-Dipolar cycloadditions of oxime or hydrazone on to the adjacent alkene occur cleanly by heating the substrate in acetonitrile, or in the case of the basic aliphatic hydrazones, under acidic conditions <1987JOC226> (Equation 40). [Pg.818]

Ketone p-toluenesulphonyl hydrazones can be converted to alkenes on treatment with strong bases such as alkyl lithium or lithium dialkylamides. This reaction is known as the Shapiro reaction68. When w./i-LinsaUi rated ketones are the substrates, the products are dienes. This reaction is generally applied to the generation of dienes in cyclic systems where stereochemistry of the double bond is fixed. A few examples where dienes have been generated by the Shapiro reaction have been gathered in Table 669. [Pg.377]

Alkyl- and aryl-hydrazones of aldehydes and ketones readily peroxidise in solution and rearrange to azo hydroperoxides [1], some of which are explosively unstable [2], Dry samples of the p-bromo- and p-fluoro-hydroperoxybenzylazobenzenes, prepared by oxygenation of benzene solutions of the phenylhydrazones, exploded while on filter paper in the dark, initiated by vibration of the table or tapping the paper. Samples were later stored moist with benzene at —60°C to prevent explosion [3], A series of a-phenylazo hydroperoxides derived from the phenyl-or p-bromophcnyl-hydrazones of acetone, acetophenone or cyclohexanone, and useful for epoxidation of alkenes, are all explosive [4], The stability of several substituted phenylazo hydroperoxides was found to be strongly controlled by novel substituent effects [5],... [Pg.336]

Phase-transfer catalytic conditions provide an extremely powerful alternative to the use of alkali metal hydrides for the synthesis of cyclopropanes via the reaction of dimethyloxosulphonium methylides with electron-deficient alkenes [e.g. 54-56] reaction rates are increased ca. 20-fold, while retaining high yields (86-95%). Dimethylphenacylsulphonium bromide reacts in an analogous manner with vinyl-sulphones [57] and with chalcones [58] and trimethylsulphonium iodide reacts with Schiff bases and hydrazones producing aziridines [59]. [Pg.284]

Other papers of interest in this section report transamination of camphor-3-carbothioamides with secondary cyclic amines, reaction of camphorquinone with dimethyl /S-ketoglutarate, the use of fenchone (212 X=0) in alkene formation from Grignard reagents, bromination of 2-e/itfo-6-endo-dibromobornane to yield 2,3,6-endo-tribromoborn-2-ene, and camphor-enol trimethylsilyl ether formation by quenching the reaction mixture of butyl-lithium and camphor tosyl-hydrazone with trimethylsilyl chloride. ... [Pg.53]

CHEC(1984) <1984CHEC(2)1> and CHEC-II(1996) <1996CHEC-II(6)1> covered examples of the cycloaddition reaction of diazoalkenes with alkenes yielding 2,3,4,5-tetrahydropyridazines. The diazadiene is normally generated in situ from an a-halogenated hydrazone with the assistance of base. [Pg.84]

The addition of zinc enolates to alkenes in the intramolecular version finds several examples in recent literature. Thus, hydrazone 155, subjected to the same treatment reported for 151 (equation 80), undergoes diastereoselective 5-exo-trig (n = 1) or 6-exo-trig (n = 2) carbocyclization to yield -156, which on reaction with the electrophile E+ gives 157 (equation 81)174. [Pg.840]

Besides the activation of the olefinic partner by a metal, the unfavorable thermodynamics associated with the addition of an enolate to a carbon—carbon multiple bond could be overwhelmed by using a strained alkene such as a cyclopropene derivative286. Indeed, Nakamura and workers demonstrated that the butylzinc enolate derived from A-methyl-5-valerolactam (447) smoothly reacted with the cyclopropenone ketal 78 and subsequent deuterolysis led to the -substituted cyclopropanone ketal 448, indicating that the carbometallation involved a syn addition process. Moreover, a high level of diastereoselectivity at the newly formed carbon—carbon bond was observed (de = 97%) (equation 191). The butylzinc enolates derived from other amides, lactams, esters and hydrazones also add successfully to the strained cyclopropenone ketal 78. Moreover, the cyclopropylzincs generated are stable and no rearrangements to the more stable zinc enolates occur after the addition. [Pg.968]

By contrast with the above examples which involve activated olefins, the addition of zinc enolates to unactivated alkenes is much more difficult to achieve. Although ethylene seems to be an acceptable partner for such additions, the reactions have to be carried out under pressure and require relatively long reaction times. Thus, the butylzinc aza-enolate generated from the SAMP hydrazone of cyclohexanone 452 reacted slowly with ethylene... [Pg.968]


See other pages where Hydrazones alkenes is mentioned: [Pg.1930]    [Pg.1930]    [Pg.141]    [Pg.75]    [Pg.22]    [Pg.343]    [Pg.1335]    [Pg.35]    [Pg.216]    [Pg.1194]    [Pg.564]    [Pg.44]    [Pg.22]    [Pg.320]    [Pg.95]    [Pg.75]    [Pg.300]    [Pg.840]   


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Alkenes from hydrazones

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