Formamidine-water

Continuous polymerization in a staged series of reactors is a variation of this process (82). In one example, a mixture of chloroprene, 2,3-dichloro-l,3-butadiene, dodecyl mercaptan, and phenothiazine (15 ppm) is fed to the first of a cascade of 7 reactors together with a water solution containing disproportionated potassium abietate, potassium hydroxide, and formamidine sulfinic acid catalyst. Residence time in each reactor is 25 min at 45°C for a total conversion of 66%. Potassium ion is used in place of sodium to minimize coagulum formation. In other examples, it was judged best to feed catalyst to each reactor in the cascade (83). 

Typically, an acetanilide (1 mol. equiv.) was treated with the Vilsmeier reagent generated from POCI3 (7 mol. equiv.) and V,V-dimethylformamide (DMF, 2.5 mol. equiv.) at 75 °C for 4 - 20 h. The reaction products were readily obtained by filtration after pouring the reaction mixture onto ice-water minor reaction products were isolated after basification of the filtrate. A variety of acetanilides were studied under these optimised reaction conditions and some significant observations were noted. Activated acetanilides 3 [e.g. R = 4-Me (70%), 4-OMe (56%)] reacted faster and in better yield to give quinolines 4 than other strongly deactivated systems 3 [e.g. R = 4-Br (23%), 4-Cl (2%), 4-NO2 (0%)] — in these cases, formamidines 5 and acrylamides 6 were the major reaction products. 

Vat dyes in general have the disadvantage that reduction to a water-soluble form is necessary before application to cellulosic textiles. Traditionally sodium dithionite in alkaline solution serves as the reducing agent. An alternative sometimes used in vat printing is thiourea dioxide, which is converted into formamidine sulphinate in alkaline solution (section 12.9.1). 

Different substrates have been tested under the following conditions 300 ml stainless steel autoclave 0.25 moles of substrate 2.0 g Raney nickel (60% in water) 1.5 g (0.014 moles) of formamidine acetate 120 ml methanol temperature 80°C H2 pressure 12 bar, 1500 rpm. 

It was shown in separate experiments that anilines can react with formamidines to give both N-mono- and N,N-diaryl formamidines which no longer are effective inhibitors. Another way of modifier deactivation is the hydrolysis to ineffective formamide by water formed during the hydrogenation of the nitro group. This could explain the rather high modifier concentration needed in order to get good selectivities. Similar observations of instability under reaction conditions have also been reported for dicyandiamide (ref. 4). 

For the reduction of water-soluble sulfur dyes, glucose and hydroxyacetone are also used [70], Glucose-based combinations with hydrosulfite, formamidine-sulfinic acid, and hydroxyacetone (binary reducing-agent systems) have gained acceptance for ecological, technical, and applicatory reasons [71], Mixtures of... 

Treatment of compound (192) with sodium hydroxide in DMSO gives the pyrimidine (196). It is most likely that this product (1%) is formed via addition of water to the C=N bond adjacent to the benzoyl group (Scheme 12). This affords the formamidine (193) which undergoes benzylic-like rearrangement to the acid (194) which cyclizes (194) - (195). Decarboxylation and N—N bond cleavage in the pyrazole moiety gives the final isolable product (196) <83CPB395i>. 

Formamidines comprise a small group of promising insecticides. Chlordimeform, formetanate, and amitraz are examples of this group. These compounds are effective against most stages of mites and ticks. Thus they am classified as ovicides, insecticides, and acariddes. Formulations are emulsifi-able concentrates and water-soluble powders. 

An aqueous solution of 1 M potassium hydroxide (1 ml) is added to a suspension of the formamidine (1 mmol) in ethanol (1 ml). The mixture is stirred at room temperature ( 1 h). The precipitated product is filtered, washed with water, a few drops of ethanol and, finally, with diethyl ether before drying under vacuum. (See Table 2.2.3.)... 

Stable nickel complexes can be isolated by chromatographic methods from the hydrogenation of 3,5-dichloro-jV,jV-diisopropyl-l24,2,4,6-thiatriazin-1-arnine. The hydrogenolysis in water gives the nickel complex of an aldimino formamidine, whereas in ethanol the nickel complex of bis(/V2-imidoylcarboximidic) acid ester is formed.45... 

Based on the pyrolysis of the neat hydrochloride salts of imidazolyl tetritols, e.g. 115a-c, which leads to the 4-glycofuranosyl-lH-imidazoles, e.g. 116a-c and their anomer mixtures, Tschamber et al. [80] obtained the same pairs of C-nucleosides in one-pot procedures by microwave irradiation with a domestic Whirlpool MO 100 oven for 1.7-3 min. Mixtures containing formamidine acetate, a few drops of water, and the appropriate hexose or hexulose, i.e. D-fructose (or o-glucose), d-galactose, or L-sorbose, resulted in overall yields of 19-28% (Scheme 12.48). Irradiation for longer periods led to caramelization. 

Another class of reactions whose understanding may require the inclusion of quantum effects consists of proton transfer reactions. The light mass of the proton indicates that such quantum effects might be quite important, but there have been attempts to simulate this process purely classically (primarily in the gas phase). An interesting method that lies in between gas phase calculations and full solution phase molecular dynamics is the supermolecule method used by Nagaoka et al. to calculate the dynamics of formamidine in water solvent. This system is quite interesting from the perspective of solution reaction dynamics because the transition state for this reaction incorporates a water molecule from the solvent. The overall process consists of two proton transfers, one from the formamidine molecule to the solvent water molecule and another one from the other end of the solvent water molecule back to the formamidine. 

Nagaoka et al. therefore treated the system consisting of the formamidine molecule and a single water molecule as a supermolecule in which the reaction dynamics takes place. They have suggested that this technique may be valuable in cases where one or two solvent molecules have a strong electronic effect on the reaction system, as is certainly the case in the formamidine system. Nagaoka et al. used ab initio calculations to determine the reaction coordinate in the supermolecule and have used this reaction coordinate as a... 

M. Nagaoka, Y. Okuno, and T. Yamabe,/. Am. Chem. Soc., 113,769 (1991). The Chemical Reaction Molecular Dynamics Method and the Dynamic Transition State Proton Transfer Reaction in the Formamidine and Water Solvent System. 

A proposed mechanism for the condensation of formamidine sulfinic acid with the dicarbonyl equivalent involves attack of the amidine nitrogen atoms on both of the electrophilic centers with loss of water. The imidazole phosphonium salt does not react directly with sodium methoxide but instead generates the reactive methylene imidazole intermediate, which is trapped by MeOH. Reactivation can be promoted in protic solvents to elongate the chain to provide cimetidine. 

Nagaoka M, Okuno Y, Yamabe T (1991) The chemical reaction molecular dynamics method and the dynamic transition state proton transfer reaction in formamidine and water solvent system. J Am Chem Soc 113(3) 769-778... 

Inclusion of an additional water molecule leading to a six-membered cycle, as in the malonaldehyde XI, provides more favorable steric conditions in XXI, XXII for proton transfer. Thus, for formamidine hydrate the calculated barrier of tautomerization XXIa XXIIb, when intermolecular mechanism is operative, (17 kcal/mol with the 3-21G and 21 kcal/mol with the 6-31G basis set) is three times lower than in the case of the intramolecular reaction Xllla Xlllb (see Sect. 9.2). 

The second part of the chapter consists of discussions of the solvent (mainly water) influence on some physical and chemical properties of the DNA bases. Following the history of these investigations, we revealed the influence of the hydration for the simple prototypic molecules as formamide, formamidine, acetamide, and N-methylacetamide, since the calculations for such molecules are the most accurate. Then we describe the results of the calculations for parent compounds of the DNA bases as pyridone, oxo-pyrimidine and amino-pyrimidine. And finally the current calculations of the hydrated DNA bases are reviewed. Because the results discussed there are, in fact, the main aim of our review, we describe the part related to the hydration of the DNA bases more specifically. 

Formamidine is another species known for detailed study of its interaction with several water molecules [70]. The cyclic mono-, di- and trihydrated complexes have been studied to evaluate the performance of a number of the DFT approximations, comparing with Moller-Plesset theory. The outcome of this study is the conclusion about the similar accuracy in the calculation of the energetic properties of the hydrated complexes at the MP2/6-31(d,p) and DFT(BH H-LYP/6-31(d,p)) levels of theory. 

A soln. of N-p-methoxyphenyl-N -(5-methyl-3-isoxazolyl)formamidine in alcohol containing Na-ethoxide heated ca. 20 min. on a water bath 1-p-methoxy-phenyl-3-acetonyl-l,2,4-triazole. Y 90%. F. e. s. H. Kano and E.Yamazaki, Tetrahedron 20, 159 (1964). 

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