Hydrazones amidines

A different type of rearrangement occurs when suitable side chains are a to a pyridine-like nitrogen atom. In the monocyclic series this can be generalized by Scheme 43. For a given side chain the rate of rearrangement is l,2,4-oxadiazoles>isoxazoles> 1,2,5-oxadiazoles. Typical side chains include hydrazone, oxime and amidine. Some examples are shown in Table 9 (79AHC(25)147). Similar rearrangements for benzazoles are discussed in Section 4.02.3.2.4. 

Carbonsaure-imid-ester Oder deren Salze werden durch Natriumboranat in neutralem Medium zu 0,N-Acetalen (s. S. 436 f.) (bzw. Aldehyden) Oder Aminen reduziert. Amidine und Imid-chloride gehen in Amine iiber, Formazane in Amid-hydrazone. 

Figure 21 Examples of aluminum complexes of phenyl hydrazones and amidines.

Inverting the orientation of the C4-N3 imine unit of a 2,3,1-diheterabotine gives a boron heterocycle with a markedly different chemical reactivity. In effect, the weakly basic oxime- or hydrazone-type imine nitrogen in the 2,3,1-diheteraborine is replaced by a much more basic imidate- or amidine-type imine nitrogen in the 2,4,1-diheteraborine. Likely, the Lewis acid tendency of the boron is enhanced by the ready protonation of this basic N4, and the formation of a stable borate-based zwitterion becomes thermodynamically favored. 

IV. Compounds With C=N Double Bond Imines, Oximes, Hydrazones, Semicarbazones, Formazanes, Amidines, and Ketimines... 

Amidine and amine groups may be joined together to form this triazepinone ring by heating the compound with methanolic sulphuric add for 3h. The reactant is obtained by stirring isatoic anhydride (review of reactions [3008]) with an amidrazone (formally, a hydrazone of a carboxamide). 

N2O2SC a-Diazosulfones a-Ketosulfone hydrazones Monosulfonylcarbodimides Sulfonylamidines Sulfonic acid amidines 5 N-Sulfonylformamidines 20 N -Sul fony Icyanamides Sulfonylformaldehyde hydrazones Sulfonylhydrazones Thiourea S-dioxides... 

K- [4-Athoxy pheny 1] N [4 oapb thoxy phenyl] but amidin 14 II 265. Santonsaure.phenylhydrazon 15, 367. y OzO -[4-methoxy-phenyl]-n-capron iare athylfi8ter plMny]hydrazon la 197. 

Amino-alkyl amides form amidines reversibly on heating and under acidic conditions. In the latter case amidines are proposed as intermediates in transamidation reactions. A full paper on a modified Shapiro reaction of hydrazones derived from secondary or-keto-amides has appeared. Ultra sound is reported to produce improvements in the heterogeneous reaction between amides and P4Sio. °... 

Aminohydrazinoboranes of the type (24) and (25) have been reported, as have salts and complexes of boron imidoyl-amidinates (26). A new method for the preparation of 2,3,1-diazaborines has been described in which aryl-sulphonyl hydrazones can be cyclized with boron halides directly to the desired product [reaction (11)]. ... 

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