Amidines amidoximes

Addition of iV-nucleophiles converts nitriles into amidoximes, amidines, amidrazones, etc., which are valuable intermediates, especially for the preparation of heterocycles. For example amidoxime prepared from p-hydroxybenzo[ C]nitrile and hydroxylamine, reacted with nicotinoyl chloride to give 3,5-disubstituted l,2,4-[3- C]oxadiazole the... 

Cyanopyridazines add ammonia, primary and secondary amines and hydroxylamine to give amidines or amidoximes. Substituted amides, thioamides and carboximidates can be also prepared. With hydrazine, 3-pyridazinylcarbohydrazide imide is formed and addition of methylmagnesium iodide with subsequent hydrolysis of the imine affords the corresponding pyridazinyl methyl ketone. 

Literature reports on synthetic methods for the construction of the pyrimidinone core were very limited. Most of the synthetic strategies toward the densely functionalized core fell into two methodologies, which start from the same amidoxime 13 (Scheme 6.3). Route A is a three-step sequence that involves hydrogenation of 13 to prepare amidine 14. Claisen condensation of commercially available a-benzyloxy acetate and methyl tert-butyl oxalate provides the dihydroxyfumarate... 

Amidines and amidoximes react with carbon disulfide and a mixture of carbon disulfide and sulfur to afford 5-mercapto-l,2,4-thiadiazole derivatives (see Section 5.08.9.3). 

In another cyclization procedure for the 1,5-benzodiazodne system, the nitriles (296) are converted to the aminodihydrodiazocines (297) (79CPB2589). Attack of nucleophiles on (297) occurs at the N-5—C-6 bond to give the 3,4,5,6-tetrahydrodiazodnes (298) with NaBH4 and the jS-aminoethylquinazolines (301) on hydrolysis. The diazocines (297) behave as typical amidines. Oxidation leads to the amidoximes (300) which on hydrolysis are converted to 2,1-benzisoxazoles (302), and reaction with diketene leads to the fused pyrimidinones (299 and l-methyl-3-one isomer) (79CPB2927). 

Alkylhydroxyamoyl chloride, 296 2-Alkylthio 6-methyltetrahydro-pyrans, 21 Amides, 101-162 Amidines, 149-153, 296 Amidoxime, 295 Analgesia,357 Analgesics, 357 Anchimeric assistance, 192 Anhydroryanodol, 265... 

Amidines, N-(l,2,4-thiadiazol-5-yl)-, rearrangement, 56, 103 Amidoximes, 1,2,4-oxadiazol-3-yl-, rearrangements, 56, 55 Amidyl radicals, see Radicals, nitrogen Amination, asymmetric, of carboxylic acids by chiral nitroso compds, 57, 41 Amines, catalysis of 3-acyl-1,2,4-oxadiazole arylhydrazone rearrangement by, 56, 87 Amines, thionitroso-, formation, 55, 20 Aminium cation radicals, see Radicals, nitrogen... 

As mentioned above, (7-aza-3-indolyl)acetonitrile (129) was reduced catalytically to give 7-azatr3rptamine (131). Other 7-azatryptamines prepared similarly are 1-methyl, 1-benzyl, 2-methyl, and l-(2-aminoethyl). This patent also describes several other 1-, 2-, and 3-(aminoalkyl) derivatives of the four azaindole isomers. The several 4-, 5-, 6-, and 7-azaindolylalkanonitriles were also treated with hydrolylamine to give amidoximes and with hydrogen chloride in chloroform, followed by ammonia to give amidines. ... 

Other derivatives of minor importance, such as thioamides, amidoximes, iminoethers, and amidines have been prepared from the corresponding cyanopyridazines. ... 

A few 6- and 8-cyanopurines have been prepared and undergo characteristic nitrile addition reactions rather readily. Thus, alkaline hydrolysis produces carboxamides, then carboxylic acids, alcoholysis leads to imidates, ammonolysis to amidines, hydrazinolysis to amidhydrazines, hydroxylamine to amidoximes, and hydrogen sulfide to thioamides. Acid hydrolysis tends to give the decarboxylated acid derivative. Reduction either by sodium-ethanol or, preferably, by catalytic hydrogenation affords aminoalkylpurines and addition of Grignard reagents produces, in the first place, acylpurines. As with aldehydes, most of the compounds examined have been relatively non-polar derivatives. Table 28 lists some reactions and relevant literature. 

These compounds have been prepared in two ways from 3-amino-l,2,4-triazines. In the first case, the aminotriazine is converted into the amidine (359) with iV,iV-dimethylfor-mamide or -acetamide acetal. Reaction of the amidine with hydroxylamine produces the amidoxime (360) and cyclization with phosphorus oxychloride forms the desired bicyclic product (361) (77JOC1018). Also, the desired ring system can be synthesized by treating 3-amino-l,2,4-triazines with acetonitrile in the presence of aluminum chloride to afford the acetamidines (362) which, in one case (R = = Me), can be transformed into... 

The reaction of amidoxime with CO using the Ru3(CO)i2 catalyst gives amidines (Eq. 11.64) [118]. 

Catalytic hydrogenation of oximes to amines requires conditions resembling those for catalytic hydrogenation of nitro compounds and nitriles.20d The catalyst should be as active as possible, e.g., Raney nickel101 (if necessary, platinized), platinum oxide,102 palladium-charcoal,103 palladium-barium sulfate,104 or rhodium-alumina.105 This rhodium catalyst also serves for reduction of an amidoxime to the amidine.106 Hydrogenation may be effected under pressure, but the temperature should be kept as low as possible to avoid formation of secondary amines. 

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