Reagents Amidines

In the first use of an amidine for this type of synthesis, 2-amino-5-methyl-N-p-tolylbenzylamine was heated with JV,JV -diphenylformamidine at 100°C to give 3-p-tolyl-6-methyl-3,4-dihydroquinazoline (see 1) (excellent yield) and two molecular proportions of aniline.62 

In a more direct attack, 4-amino-5-aminomethyl-l-methyl-l,2,3-triazole (see 20) was refluxed with a suspension of formamidine acetate a quantitative yield of 7-methyl-l,6-dihydro-8-azapurine (see 21) was obtained.60 The presumed intermediate (68) was not isolated (but see ref. 63). 

This reaction was extended to the 2-methyl and 3-benzyl analogs of the starting material, making use of formamidine, acetamidine, and trichloro-acetamidine. Butanol proved to be the best solvent, and condensation times from 1 to 4 hr gave good to excellent yields. Neither the free bases nor the hydrochlorides of the amidines gave much product. It was thought that the free amidines were rather unstable under the conditions of the reaction and that the acetates furnished a steady supply of them.60 

Steric hindrance was encountered in applying this reaction to the synthesis of 1- and 3-methyl-8-azapurines. Thus, 4-amino-3-benzyl-5-methylamino-methyl-l,2,3-triazole reacted so slowly with formamidine acetate in boiling butanol that the amidine underwent destruction this situation was remedied by feeding in new supplies of the amidine every 2 hr, giving an excellent yield of 9-benzyl-l,6-dihydro-l-methyl-8-azapurine.63 

Under these conditions, the even less reactive 5-aminomethyl-3-benzyl-4-methylamino-l,2,3-triazole gave some of the 5-formamidomethyl analog, but no 9-benzyl-3,6-dihydro-3-methyl-8-azapurine (69). An attempt to cyclize this formyl derivative by heating at 200°C caused it to undergo a Dimroth retrogression to 4-benzylamino-5-formamidomethyl-3-methyl-1,2,3-triazole other attempts to close the ring also failed.64 

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By using an alternate synthetic route, a mono(amidinate) magnesium complex was obtained. In this case, the Giignard reagent formed by treatment of the terphenyliodide with Mg was allowed to react directly with 1 equivalent of 1,3-diisopropylcarbodiimide, yielding the amidinate (Scheme 18). ... 

As representative examples for the reactivity of the Cp Ti(amidinate) complexes some reactions with CS2 and COS are shown in Scheme 88. Other reagents that have been investigated in this study include carbodiimides, isocyanates, CO2, PhNO as well as aldehydes, ketones, and imines. ... 

These lithium derivatives were found to be excellent reagents for the introduction of the new amidinate scorpionate ligands into Group 4 metal complexes, and a series of neutral titanium and zirconium complexes were prepared according to Scheme 189 and fully characterized. 

KOH is the most frequently used base, though stronger bases (OR , NH, etc.) or weaker ones (e.g., amines) are used where warranted.The bicyclic amidines l,5-diazabicyclo[3.4.0]non-5-ene (DBN) and are good reagents... 

It has been found that DTBP cross-linking substantially increased the salt stability of the complexes. The salt stabilization is reversed upon the addition of DTT, which cleaves the bifunctional reagent, indicating that it is not due to the conversion of the amines to amidines and is dependent upon the cross-linking. Similar results were achieved with other polycations, including poly(allylamine), and histone HI. 

With RCH2CN, however, there is a tendency for Grignard reagents to remove a proton from the CH2 group, leading to more complex reactions. Reduction with Li AlH4e (c/. p. 214) yields RCH2NH2, NH3 adds to (193), in the presence of NH4 Cle to yield salts of amidines, RC(NH2)=NH2 Cle. Acid-catalysed addition of alcohols,... 

Luminol amidine 132, synthesized from luminol and the Vilsmeier reagent from DMF and thionyl chloride, has been proposed as a suitable luminol derivative for analytical purposes because, unlike luminol, it can be easily purified by recrystallization from water. 132 exhibits a chemiluminescence quantum yield of about 20% of luminol in ferricyanide-catalyzed oxidation by aqueous alkaline hydrogen peroxide Amax of the emission is 452 nm 196>. 

The direct nitration of imidazole with acidic reagents is difficult due to facile nitrogen protonation (pA aH 7). Nitration of imidazoles proceeds in the 4- and 5-positions with the amidine 2-position being quite inert. Imidazole can be directly nitrated to 4,5-dinitroimidazole but no further. 2,4,5-Trinitroimidazole (TNI) can be prepared from the successive nitration of 2-nitroimidazole the latter synthesized from the diazotization of 2-aminoimidazole in the presence of excess sodium nitrite and a copper salt. The nitrative cleavage of polyiodoimidazoles also provides a route to polynitroimidazoles. " ... 

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