Benzamidine, reaction with ester

The synthesis of pyrido[2,3-d]pyrimidin-7(8H)-ones has also been achieved by a microwave-assisted MCR [87-89] that is based on the Victory reaction of 6-oxotetrahydropyridine-3-carbonitrile 57, obtained by reaction of an Q ,/3-unsaturated ester 56 and malonitrile 47 (Z = CN). The one-pot cyclo condensation of 56, amidines 58 and methylene active nitriles 47, either malonitrile or ethyl cyanoacetate, at 100 °C for benzamidine or 140 °C for reactions with guanidine, in methanol in the presence of a catalytic amount of sodium methoxide gave 4-oxo-60 or 4-aminopyridopyrimidines 59, respectively, in only 10 min in a single-mode microwave reactor [87,88]... 

Benzamidine reacts with the pyrazinooxazinone 14 at room temperature to give the acylamidine 15. Guanidines react similarly to give the acylguanidines 16. This approach to acylguanidines is particularly useful when the guanidine component is insufficiently nucleophilic to react directly with esters of pyrazine amino acids. The reaction has been extended to other substituted pyrazine amino acids. ... 

Kinetic studies of the n-butylaminolysis of p-nitrophenyl triphenyl-methanesulphenate reveal second-cHrder characteristics, while reaction with benzamidine is first-order, as it is with carboxylic esters. S—O versus C—O fission has been contemplated for solvolysis of benzyl trichloromethanesulphenates, which provide the first example of C—O fission, to give Cl2C=S=0. Ethyl benzenesulphenate reacts with phosphites to give... 

Alternatively, the remaining sulfate ester of 70 may serve as a leaving group for a second nucleophilic displacement reaction. When this displacement is by an intramolecular nucleophile, a new ring is formed, as was first shown in the synthesis of a cyclopropane with malonate as the nucleophile [68] and of aziridines with amines as the nucleophiles [76]. The concept is further illustrated in the double displacement on (/J,/ )-stilbenediol cyclic sulfate (72) by benzamidine (73) to produce the chiral imidazoline 74 [79]. Conversion of the imidazoline (74) to (.V,.S )-stilbenediaminc 75 demonstrates an alternative route to optically active 1,2-diamines. Acylation of 75 with chloroacetyl chloride forms a bisamide, which, after reduction with diborane, is cyclized to the enantiomerically pure trans-2,3-diphenyl- 1,4-diazabicy-clo[2.2.2]octane (76) [81],... 

The homoleptic lanthanide(III) benzamidinates 20-23 can be regarded as analogues of the well known tris(cyclopentadienyl)lanthanide complexes (C5H5)3Ln [7, 8]. One of the most characteristic reactions of the homoleptic cyclopentadienyls is the formation of 1 1 adducts with Lewis bases such as ethers, nitriles, esters etc. [7, 8], Recently it was discovered that the homoleptic lanthanide benzamidinates [PhC(NSiMe3)2]3Ln (20) form similar adducts with THF and nitrile ligands such as acetonitrile or benzonitrile [59]. The molecular and crystal structures of two benzonitrile adducts (26g, h) have been determined by X-ray diffraction. Figure 8 depicts the molecular structure of the europium... 

Schematically shown in Fig. 5 is the preparation of an enzyme mimic for the hydrolysis of ester 6 by molecular imprinting. Phosphonate 5 is an analog of the transition state for the alkaline hydrolysis of Ester 4. It was used as a template for polymerization with two equivalents of the binding-site monomer iVJV -diethyl-4-vinyl-benzamidine. Amidinium groups were chosen, because they can interact electrostatically with the side carboxyl-ate group as well as with the anionic transition state of the alkaline hydrolysis, thus achieving substrate recognition and transition-state stabilization. Polymerization of the preassembled binding-site monomer with the template (Fig. 5A) followed by template removal (Fig. 5B) leaves a cavity that acts as transition-state receptor for the ester substrate (Fig. 5C). The imprinted polymer accelerates the hydrolysis of 6 more than 100-fold compared to the reaction at the same pH in buffer solution without the polymer. The reaction kinetics is of the Michaelis-Menten type. A polymer obtained with amidinium benzoate as a control, with a statistical distribution of amidinium groups, is ca. one order of magnitude less active in the hydrolysis of 6.

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