Allenic hydrazines

Recently, the scope of gold-catalyzed intramolecular exo-selective hydroaminations was expanded to allenic hydrazines and hydroxylaminesJ The former substrates afforded pyrazolidines in the presence of DTBM-SEGPHOS-Au complex J, whereas [Au2 (R)-xylyl-BINAP (OPNB)2] gave the best results in the cyclization of hydroxylamine derivatives to isoxazolidines. Excellent chemical yields and enantioselectivities were obtained in most cases, and the method was also applied to the synthesis of chiral tetrahydrooxazines. 

Representative procedure for the gold-catalyzed cycloisomerization of allenic hydrazines. t-Butyl 2-(mesitylsulfonyl)-3-(2-methylprop-l-enyl)pyrazolidine-l-carbaxylat ... 

Ethyl carhazate (A-ethoxycarhonyl hydrazine) [4114-31-2] M 104.1, m 44-48 , 51-52 , h 95.5 /10m, 92-95 /12mm, 100-102 /llmm. Fractionated using a Vigreux column until the distillate crystallises [Allen and Bell Org Synth Coll Vol III 404 1955.]... 

One of the most dramatic developments in the chemistry of N2 during the past 30 years was the discovery by A. D. Allen and C. V. Senoff in 1965 that dinitrogen complexes such as [Ru(NH3)5(N2)1 could readily be prepared from aqueous RUCI3 using hydrazine hydrate in aqueous solution. Since that time virtually all transition metals have been found to give dinitrogen complexes and several hundred such compounds are now characterized.Three general preparative methods are available ... 

A number of reaction pathways have been proposed for the Fischer indolization reaction. The mechanism proposed by Robinson and Robinson in 1918, which was extended by Allen and Wilson in 1943 and interpreted in light of modem electronic theory by Carlin and Fischer in 1948 is now generally accepted. The mechanism consists of three stages (I) hydrazone-ene-hydrazine equilibrium (II) formation of the new C-C bond via a [3,3]-sigmatropic rearrangement (III) generation of the indole nucleus by loss of... 

Under the same reaction conditions, -keto esters which have been alkylated on the a-carbon atom (thus leading to 3,4-disubstituted 5-pyrazolones upon treatment with hydrazine) give allenic esters in good (50-70%) yield (158). The mechanism (Scheme 36) again appears to involve thallation of the enamine tautomer of the 5 -pyrazolone, but deprotonation now takes place... 

Coupling of excess (Z)-l,2-dichloroethene (217) with propargyl alcohol first led to the enyne 218, which, when subjected to a second Pd-catalyzed coupling step with trimethylsilylacetylene, provided the mixed diacetylene 219. With all carbon atoms assembled, the allene function was generated by first producing the (unprotected) hydrazine derivative 220, which on treatment with either diethyl azodicarboxylate (DEAD) or 4-methyl-l,2,4-triazoline-3,5-dione (MTAD) under anaerobic conditions at 0 °C yielded the hydrocarbon 27. According to mechanistic studies, the latter process leads first to a mixture of ( )- and (Z)-diazenes. Sigmatropic elimination of... 

Treatment of 3-allyl-3-(2-propynyl)-2,4-pentanedione with methyl-hydrazine to give condensation and propargyl-allene rearrangement [118]. 

P. Walden34 has studied soln. of iodine in acetaldehyde, hydrazine hydrate, and acetonitrile J. H. Mathews, soln. of iodine in pyridine, ethyl, allyl, and plienyl isothiocyanic esters, and phenyl isocyanate while H. A. Allen has studied soln. of bromine and iodine in various oils. 

Oxidation of hydrazines to diazines. Propargylic hydrazines are oxidized rapidly and efficiently in CH3OH at 0° by 4-methyl-l,2,4-triazoline-3,5-dione (MTAD) or diethyl azodicarboxylate (DEAD) with evolution of nitrogen to provide the corresponding allenes in 50-70% yield. The reaction occurs with high stereospecificity, and can be used to obtain optically active allenes (equation I).1... 

In the majority of cases alkyl hydrazines give single pyrazoles.160, 328, 336,337 In 1958 Bertrand established that allenic ketones give pyrazoles quantitatively with hydrazine.338 The reaction may be formulated as follows, the second stage being stabilization by aromatization. Acetylenic nitriles give aminopyrazoles with hydrazine.339... 

Simple and complex hydrazides, with the general formula RCONHNHCOR, were readily dehydrogenated by DIB to the corresponding azo compounds, some of which were used as dienophiles for in situ Diels-Alder reactions [65,66]. Hydrazine itself in the form of its hydrate was similarly converted into diimide, NH — NH, which served for some in situ hydrogenations [67], Further reactivity accompanied by solvent participation was observed in some cyclic derivatives of hydrazine, i.e. pyrazolones. At low temperature these underwent ffagmentive loss of dinitrogen to give either methyl alkynoates or allenic esters [68] ... 

The preparation of the hexaammine complexes of ruthenium(II) and ruthenium (III) salts are sketchily described in the literature. The preparation of hexaammineruthenium(II) by the reduction of ruthenium trichloride with zinc in ammonia is described briefly by Lever and Powell.1 Allen and Senoff2 carry out the reduction using hydrazine hydrate. The hexaammineruthe-nium(III) cation is obtained by oxidation of the ruthenium(II) complex,1 and pentaamminechlororuthenium(III) dichloride is obtained by treating the former compound with hydrochloric acid.1,3 This compound may also be obtained by treating the pentaammine molecular nitrogen complex of ruthenium(II) with hydrochloric acid.2,4... 

Altenic esters. 2 a-Alkyl-/l-keto esters (1)13 can be converted into allenic esters (6) by treatment with 1 eq. of hydrazine, to form the 3,4-disubstituted 5-pyrazolone (2), and then with a solution of 2 eq. of TTN in methanol. Isolation of the intermediate pyrazolone is unnecessary. Overall yields of allenic esters are in the range 50-70%. Note that R, must be an alkyl group, otherwise a, -acetylenic esters are formed (see above). The conversion of 5-pyrazolones (2) into allenic esters (6) is explained by electrophilic... 

Dehalooenation Chromous chloride. Copper powder-Benzoic acid. Dimethyl sulfoxide-NaH. Hydrazine-Palladium. Iron pentacarbonyl. Lithium-l-Butanol-THF. Magnesium-Iodine-Ether. Methyllithium. Sodium acetate. Sodium iodide. Zinc dust. Zinc dust-Ethanol (see Allene, preparation. Hexafluoro-2-butyne, preparation). 

Other applications are studies of rotation about double bonds 136>, ring inversion in cyclooctatetraene 137>, the insertion of carbon into ethylene and. fraws-2-butene to give allenes 133), the barrier height to inversion of nitrogen in hydrazine and alkylamines 133>, the Cope... 

Reduction of allenes. Cyclic and acyclic allenes are reduced stereospecifically by diimide (generated from hydrazine, H2Oa, CuS04) to cis-alkenes.6... 

The first dinitrogen complex of a transition metal was discovered by Allen and Senoff (1965). They attempted the synthesis of the hexaamminoruthenium complex [Ru(NH3)6] + by the reaction of hydrazine with ruthenium trichloride trihydrate in water, and they found that the dinitrogen complex [Ru(NH3)5(N2)] (3.16) was formed. The origin of dinitrogen was disproportionation of hydrazine in situ, with simultaneous formation of ammonia (3-19 and 3-20). 

---