Diazabicyclooctane

Normally the reaction Is useful for the conversion of alkyl halides to primary amines without concomitant formation of secondary amines.29 Treatment of polymer 17 with hexamethylenetetramine in a mixture of ethanol/THF afforded an insoluble resin. Using diazabicyclooctane (DABCO), we demonstrated that the reaction could be limited to attack by a single nitrogen in a multifunctional amine, so we did not anticipate crosslinking via bis-quat salt formation. Hydrolysis of 2 with anhydrous HC1 in ethanol generated free amino groups as evidenced by a positive ninhydrin test, but quantitative hydrolysis could not be achieved and the product remained insoluble. One would have expected a simple bis-quat to hydrolyse and open the crosslinked structure. 

A commercially available 5% palladium on activated carbon catalyst from Degussa was used for the investigation. Commercially supplied N-(Carbo-benzyloxy)-L-phenylalanine (99%) was purchased from Aldrich. Modifiers such as pyridine, triethylamine, ethylenediamine and DABCO (Diazabicyclooctane) with a purity >99 % are also available commercially and were used as received. 

A-Halogeno-amides are familiar and convenient sources of positive halogen for the organic chemist, and the 2 1 complex formed in benzene between diazabicyclooctane (DABCO) and /V-bromsuccinimide (NBS) [48] (the numbers are the observed interatomic distances in angstroms) in effect shows one such reagent in action (Crowston et al., 1984). The N-Br-N angle is close to linear [175.1(2) A], and the bromine is poised almost midway between the two nitrogen atoms, which are of similar basicity. The... 

A much more supramolecular example of ion-ion interactions is the interaction of the frrs(diazabicyclooctane) host (1.17), which carries a 3+ charge, with anions such as [Fe(CN)6]3-(Figure 1.13b).15... 

This procedure has been utilized to condense iV-benzyl protected azomethine ylid with iV-benzyl maleimide as the initial step in the preparation of heterocyclyl-substituted diazabicyclooctanes having a EC50 < 500 nM, being selective agonists of 5-HTl-like receptors and potent agonists for the human 5-HTlDa.414... 

We have investigated a variety of clusters with ethers and amines as the Rydberg donor systems and polar solvents as the acceptors. The donors we have studied include dioxane (C4H802), azabicyclooctane (ABCO), diazabicyclooctane (DABCO), hexamethylenetetramine (HMT), and others (Moreno et al. 1992 Shang and Bernstein 1994 Shang et al. 1993a,b,c, 1994a,b,c). The acceptors include ethers, amines, and aromatics. 

Cyclic oligomeric oxolanyl alkanes were used when diene polymerization utilized a lithium-based initiator. Cyclic oligomeric oxolanyl alkanes are described by Lin [1] and include 2-2 -di(tetrahydrofuryl) propane, dipiperidyl ethane, hexamethyl phosphoramide, N-N -dimethyl piperazine, and diazabicyclooctane. 

Molecular complexes can be prepared from some tertiary amines and 90 or 30% solutions of hydrogen peroxide. 1,4-Diazabicyclooctane (Dabco) forms an adduct with two molecules of hydrogen peroxide. The adduct consists of hygroscopic crystals melting at 112 °C (dec), is stable for a limited time at room temperature, and can be used as a source of hydrogen peroxide in oxidations [727]. 

According to Burkus, the lower basicity and the higher nucleophilicity of 1,4-diazabicyclooctane favor the formation of the complex between the base and the isocyanate and minimize the interaction between the base and the alcohol. Thus, at low base concentrations, a direct proportionality exists between the base concentration and the base-isocyanate complex concentration. 

As an example of an amine of unusually high catal3dic activity, Farkas et al. studied the 1,4-diazabicyclooctane catalyzed reaction of phenyl isocyanate with 2-ethylhexanol 39). This amine is a di-tertiary base, N (C2H4)3N, with the N atoms at the bridge heads. The reaction was found to follow the second-order kinetics, and the rate of reaction was proportional to the diazabicyclooctane concentration. The temperature dependence of the uncatalyzed and the catalyzed reaction between the 23° and 47° corresponds to an energy activation of 11.1 and 5.5 kcal./mole for the uncatalyzed reactions, respectively. 

A comparison of the catalytic constants as defined by Baker for diazabicyclooctane and the structurally related triethylamine, ,4-dimethyl-... 

Under the assumption that Baker s mechanism is valid, Farkas and Flynn draw the following conclusions from their results. The rate of the catalyzed reaction depends on the concentration of the amine complex and on the specific velocity constant for the reaction which involves this complex and the alcohol. Since the diazabicyclooctane is free from steric hindrance and the nitrogen atoms are readily accessible to the reactants, the formation of the complex between this molecule and the isocyanate molecules takes place more readily than with an amine having a carbon-nitrogen bond capable of free rotation around the nitrogen. Related to the postulate of higher... 

The dependence of the catalytic activity on the steric requirement of the base does not support a mechanism which involves a base-alcohol interaction resulting in the formation of an alkoxide ion, since such a mechanism would not be sensitive to steric factors because of the small space requirement of the proton. The basicity of an amine is not connected with the steric requirement of the base. The mechanism involving ion formation cannot account for the high activity of 1,4-diazabicyclooctane, quinine, or 1,2-dimethylimidazole. The low activity of the tetraethylmethanedi-amine and dimorpholinomethane are also inconsistent with the ionic mechanism. 

The progress of the reaction with time in dioxane at 23° in the presence of diazabicyclooctane as the catalyst did not conform to second-order kinetics as the reaction tended to proceed faster than required by second-order kinetics after half of the isocyanate had been consumed. This effect... 

Fuchigami et al. reported the electrooxidative N—N coupling of dia-zocine 222. Use of platinum, carbon, and nickel electrodes afforded the diazabicyclooctane 223 and dihydropyrazole 224, whereas use of a silver electrode yielded only the latter compound (78CL1473 80BCJ2040). (For the reverse of the 222 — 223 closure, see Section II,B,2). 

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