Hydrazonium salts

The hydrolysis of the diaziridine 34 to the cyclic hydrazonium salt 61 [Eq, (49)] occurs quantitatively. Hydrolysis of the diaziridino-triazolidine (37) gives 3 moles of aldehyde and 1 mole each of hydrazine and ammonia [Eq. (50)]. ... 

Quaternary hydrazonium salts (derived from aldehydes) give nitriles when treated with OEt or DBU (p. 488, 1337) as do dimethylhydrazones RCH— NNMe2 when treated with Et2NLi and HMPA. All these are methods of converting aldehyde derivatives to nitriles. For the conversion of aldehydes directly to nitriles, without isolation of intermediates, see 16-21. 

J. J. Eddine, M. Cherqaoui, Chiral Quaternary Benzo-phenone Hydrazonium Salt Derivatives Efficient Chiral Catalysts for the Enantioselective Phase-Transfer Alkylation of Imines. Application to Synthesis of Chiral Primary Amines , Tetrahedron Asymmetry 1995, 6, 1225-1228. 

Ring contraction of iV-phenylpyridopyridazine hydrazonium salts 118 or 119 into iV-phenylaminoimide 120 was performed by boiling in 80% AcOH (Equation 8) <1998FA468>. 

Formic acid does not react at all in alkaline solutions carbon monoxide reacts better in alkaline than in acid solutions. Most surprisingly, no reaction at all can be produced with hydrogen, which under other conditions is readily oxidized. Hydrazine, which is present in adds almost exclusively as the corresponding hydrazonium salt, is very easily oxidized. This suggests that hydrazine reacts directly and not by the mechanism of previous separation of hydrogen. 

Quaternary hydrazonium salts (derived from aldehydes) give nitriles when treated with OEr391 or DBU (p. 1023) 392... 

Treatment of the hydrazonium salt (93) with 10% hydrochloric acid gives the rearranged product (94). The proposed mechanism for this ring contraction is shown (72CPB1513). 

They are decomposed by this means to their starting materials, the azomethinimines of 3,4-dihydroisoquinoline (92), and the carbonyl compound. This is recognizable by a color change to reddish-brown. Acid hydrolysis of 91 produces the hydrazonium salt of 92 and the... 

Attempted synthesis of the bis(2//-azirine) system from the 2,3-dimethyl-1,4-diphenyl-1,4-butane-dione bis(hydrazonium) salt under basic conditions gives 3,4-dimethyl-2,5-diphenylpyrrole in 89% yield (equation 66). ° ... 

A related amino-Heck cyclization of hydrazonium salts has been discovered by Narasaka. For example, 258 is smoothly converted to pyrrole 259 in 81% yield [158]. 

Treatment of hydrazonium salt 4 with palladium(0) led to the formation of p3UTole 5 via 5-exo-trig amino-Heck cyclization <05H(65)273>. The reaction presumably proceeds by the oxidative addition of palladium(O) into an A-Abond. An oxidative addition into the A-O bond of benzoyloximes was the key step in the 5-endo-trig amino-Heck cyclization leading to 5-fluoro-3A-pyrroles <05CC4684>. 

Bloink and Pausacker suggested a mechanism similar to that of Braude and Forbes, in which the hydrazonium salt, instead of oxidizing the hydroxyl group, oxidizes the hydrazino hydrazone formed by the action of phenyl hydrazine on the phenylhydrazone by way of (7). The hydrazino hydrazone is also an intermediate in the Weygand scheme B (see p. 145) for ketoses, where it is produced by an Amadori rearrangement. 

Hydrazonium salts (117) with sodium hydride in DMSO give azirines (118), which react further with ketones to give 2f/-pyrroles (119) benzyl cyanide similarly gives 120 (Scheme 43).114-116 This reaction is claimed to be the most convenient general route to 2H-pyrroles (yields 20-80%).114... 

Hydrazonium salts derived from aldehydes are known [70] to undergo a Hofmann-like elimination when treated with a base ... 

Aziridines from quaternary hydrazonium salts with C-substitution s. 32, 431 ... 

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