Pyridine 2-hydrazino

Thieno[3,2-c]pyridine, 4-hydrazino-cyclization, 4, 1014 Thieno[3,2-c]pyridine, 3-hydroxy-... 

Cyclization of the 5-(A -arylcarboxamido)-4-hydrazino-6methylpyrim-idin-2-ones 104 with two molar equivalents of formaldehyde in the presence of pyridine caused the concomittant triazole and pyrimidine ring formation to yield the 4-aryl-l,3,4,10-tetrahydro-6-methyl-l,2,4-tria-zolo-[2,3,4-c,d]pyrimido[4,5-d]pyrimidine-5,8-diones 105 (89AP599)... 

Chloro-1 -methyl-3-trifluoromethyl- //-[ 1,3,4]oxadiazmo[5,6-fc]quinoxaline (570) suffered thiolytic ring fission in refluxing pyridine (containing phosphorus penta-sulfide) during 1 h to provide 7-chloro-3-[7/-methyl-A( -(triiluoroacetyl)hydrazino]-2(17/)-quinoxalinethione (571) in 87% yield. ... 

Hydrazinoquinoxaline gave 2- [ot-(pyridin-2-yl)benzyhdene]hydrazino qui-noxaline (233) (2-benzoylpyridine, MeOH, trace AcOH, reflux, <12 h ... 

Note Many of the (substituted hydrazino)quinoxalines covered in this section have been converted into metal complexes, randomly exemplified here. 2-(Pyridin-2-ylhydrazonomethyl)quinoxaline (246) Fe(ll), Ni(ll), and Cu(ll)... 

MethyM-cthoxycarbonyl-5-bcnzoyl-hydrazino-l //-pyrazole 274, prepared by reacting benzoyl chloride and 3-methyM-cthoxycarbonyl-5-bcnzoyl-hydrazino-l //-pyrazole hydrochloride 273, in the presence of pyridine in acetonitrile, has been cyclized with phosphoryl chloride in benzene or toluene to give 7-ethoxycarbonyl-6-methyl-3-phenyl-l //-pyrazolo[5,l -/ 1,2,4 triazolc 55. This compound has been also synthesized through cyclization of... 

TosN, (0.37 g, 2 mmol), the arylhydrazine (2 mmol), and TEA-Br (0.1 g, 0.5 mmol) in xylene (10 ml) are added to aqueous NaOH (50%, 10 ml) and the mixture is refluxed until the azide has been fully consumed (2-10 h). The organic phase is separated and the aqueous phase is extracted with PhH (3 x 10 ml). The combined organic solutions are dried (MgS04) and evaporated to yield the arene [e.g. PhH 40% (6 h) pyridine 98% (6 h) from 2-hydrazino derivative pyridazine 79% (8 h) from 3-hydrazino derivative)]. 

PADP (171), an explosive synthesized from the reaction of 3,5-dinitro-2,6-bis-(hydrazino)pyridine with picryl chloride in DMF followed by oxidation with nitric acid, also exhibits high thermal stability. 2,4,6-Tris(picrylamino)-3,5-dinitropyridine (172) exhibits much lower thermal stability than both PYX (170) and PADP (171), a consequence of increased steric crowding around the pyridine ring. ° ... 

Bromo substituents in the 6- and 6 -positions of 2,2 -bipyridines are particularly reactive, being readily converted to amino,cyano, ° al-koxyl, hydrazino, chloro, and hydrogen groups and by way of the corresponding lithio derivatives to carboxyl, methyl, aldehyde or alkylcarbonyl, and other groupings. 6,6 -Dibromo-2,2 -bi-pyridine also reacts with the disodium derivatives of polyethylene glycols to give crown ethers akin to 100, and 6,6 -bis(chloromethyl)-2,2 -bi-pyridine " and the derived 6,6 -bis(mercaptomethyl)-2,2 -bipyridine... 

Only very powerful nucleophilic reagents such as HO-, NHJ, RLi, LAH, etc., react effectively at the ring carbon atoms of simple pyridines (c/. equation 22), and even then forcing conditions may be required. Oxidation of pyridine to 2-pyridone with potassium hydroxide, for example, requires a temperature of ca. 300 °C. Nevertheless, some of these reactions can be of very considerable synthetic importance, especially the classical Chichibabin reaction for the preparation of 2-amino, alkylamino and hydrazino heterocycles (equation 28). The sequence of substitution is C-2, then C-6 and finally C-4. The Chichibabin reaction also requires rather vigorous conditions and often proceeds in only moderate yield the simplicity of the approach, however, is such that it often represents the method of choice for the preparation of the requisite substituted heterocycle. 

Pyridine reacts with sodium hydrazide in the presence of hydrazine to yield 2-hydrazinopyridine in the absence of free hydrazine a hydrazo compound is formed (Scheme 88) (64AG(E)342). A difference between hydrazination and amination is the formation of 1,4-adducts which cannot be rearomatized even on heating. This is reflected in the behaviour of quinoline, which gives only a 0.5% yield of a -hydrazino product, whereas 4-methylquino-line is hydrazinated in 76% yield (64AG(E)342). Acridine behaves differently with sodium hydrazide/hydrazine, 9,10-dihydroacridine is formed almost quantitatively, but reaction in the absence of hydrazine yields 9-aminoacridine (65%). An even higher yield of 9-amino-acridine is obtained when sodium Af.AC-dimethylhydrazide is used (Scheme 89). Good evidence for intermediacy of (151) comes from the isolation of (152) on hydrolysis of (151). 

Allerdings erfolgt mit 2-Hydrazino-pyridin- und 2-Hydrazino-ehinolin-Hydrochlorid ohne Zwischenstufe Ringumwandlung zu 3-(2-Acyl-hydrazino)-[Pg.618]

Dipyridyl-hydrazine lassen sich aus 3,5-Dinitro-pyridinen und Hydrazin gewinnen. Hierbei entsteht je nach den Reaktionsbedingungen 3,5-Dinitro-2-hydrazino-pyridin oder... 

A similar series of nucleophilic substitutions has been performed on 4-chloro[l,2,3]triazolo[4,5-c]pyridine (246) and some of its simple substituted derivatives. On compound 246 itself formic acid gives the triazolo-pyridin-4-one,192 ammonia gives the 4-amino compound,192 and hydrazine the 4-hydrazino derivative 245 hydrosulfide gives the 4-thione192 and thiourea in propanol, at first reported151 to give the 4-thione, has subsequently been... 

JV-Nitraminopyridines are reducible both in acid and alkali. In hydrochloric acid the main product from 2-nitraminopyridine was the hydrazino-pyridine, formed in a six-electron reduction, but 2-aminopyridine and 2-chloropyridine were side products, the latter possibly through reaction by an intermediate diazonium compound with chloride. Contrary to nitramines of most primary amines, 2-nitraminopyridine431 is reducible in alkaline solution uptake of the first two electrons forms the 2-pyridyl-N-nitrosamine, which is further reduced to 2-aminopyridine. 

The synthesis of the nucleoside 594 was performed by the reaction of the hydrazino derivatives 593 with acetic anhydride at room temperature. Deacetylation of 594 gave (2-deoxy-/3-D-ribofuranosyl)triazolopyrimidine (595). Reaction of 593 with acetic formic anhydride in dry pyridine followed by treatment with ammonia/MeOH gave the triazolo[4,3-c]pyrimi-dine nucleoside 596 (91MI4) (Scheme 118). 

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