Nitrogen heterocycles amination

It melts at 39°C and may be purified by vacuum sublimation. The Hquid boils at 233°C to give a monomeric vapor in which the Ti—Br distance is 231 pm. Titanium tetrabromide is soluble in dry chloroform, carbon tetrachloride, ether, and alcohol. Like titanium tetrachloride, TiBr forms a range of adducts with molecules such as ammonia, amines, nitrogen heterocycles, esters, and ethers. 

Hydrogenolysis of metal carbonyls, such as Mnj(CO)jg [250 atm (25 MPa), 200°C] or COjCCOg [250 atm (25 MPa), 110°C], leads to metal-metal bond cleavage, forming HMn(CO)j or HCo(CO) The conversion of CoJiCO to HCo(CO) is the rate-determining step in Co-catalyzed hydroformylations at high P and T. Tertiary amines, nitrogen heterocycles, tertiary phosphorus bases or halide ions enhance the rate of HCo(CO) formation e.g., pyridine can increase the rate of HCo(CO).j formation 300-fold at 40°C. 

In the case of lubricant dispersants, the polar part is organic (amine, polyamine, heterocyclic nitrogen compounds, polyglycol). 

The spectroscopic properties of the /V-nitrosamines, especially the nmr and mass spectra, vary widely depending on the substituents on the amine nitrogen (44—47). The nmr spectra are affected by the E—Z isomerism around the N—N partial double bond and by the axial—equatorial geometry resulting from conformational isomerism in the heterocycles (44,45). Some general spectral characteristics for typical dialkylnitrosamines and simple heterocycHc nitrosamines are given in Table 1. 

The nitrogen of aHphatic and aromatic amines is alkylated rapidly by alkyl sulfates yielding the usual mixtures. Most tertiary amines and nitrogen heterocycles are converted to quaternary ammonium salts, unless the nitrogen is of very low basicity, eg, ia tn phenylamine. The position of dimethyl sulfate-produced methylation of several heterocycles with more than one heteroatom has been examined (22). Acyl cyanamides can be methylated (23). Metal cyanates are converted to methyl isocyanate or ethyl isocyanate ia high yields by heating the mixtures (24,25). 

Synthesis of the title compound is representative of a number of syntheses of nonaromatic nitrogen heterocycles via Pd(Ill-catalyzed amination of olefins. These tosylated enamines are not readily available by standard synthetic methods, and show potential for further functionalization of the heterocycle. The saturated amine can be synthesized from the title compound by hydrogenation of the double bond followed by photolytic deprotection. ... 

CaveU and Chapman made the interesting observation that a difference exists between the orbital involved in the quatemization of aromatic nitrogen heterocycles and aromatic amines, which appears not to have been considered by later workers. The lone pair which exists in an sp orbital of the aniline nitrogen must conjugate, as shown by so many properties, with the aromatic ring and on protonation or quatemization sp hybridization occurs with a presumed loss of mesomerism, whereas in pyridine the nitrogen atom remains sp hybridized in the base whether it is protonated or quaternized. Similarly, in a saturated compound, the nitrogen atom is sp hybridized in the base and salt forms. 

As discussed in Chapter 6, nitro compounds are converted into amines, oximes, or carbonyl compounds. They serve as usefid starting materials for the preparation of various heterocyclic compounds. Especially, five-membered nitrogen heterocycles, such as pyrroles, indoles, ind pyrrolidines, are frequently prepared from nitro compounds. Syntheses of heterocyclic compounds using nitro compounds are described partially in Chapters 4, 6 and 9. This chapter focuses on synthesis of hetero-aromadcs fmainly pyrroles ind indolesi ind saturated nitrogen heterocycles such as pyrrolidines ind their derivadves. 

Polyoxylated amines, amides, and imidazolines Nitrogen heterocyclics... 

In addition to bromides and iodides, the reaction has been successfully extended to chlorides,163 triflates,164 and nonafluorobutanesulfonates (nonaflates).165 These reaction conditions permit substitution in both electron-poor and electron-rich aryl systems by a variety of nitrogen nucleophiles, including alkyl or aryl amines and heterocycles. These reactions proceed via a catalytic cycle involving Pd(0) and Pd(II) intermediates. 

Corrosion inhibition is primarily associated with acidizing. Buffered hydrofluoric acid compositions have been shown to be less corrosive (147). Corrosion inhibitors are designed to reduce the rate of reaction of fluid with metal surfaces, generally by forming films on the surfaces. Acetylenic alcohols and amines are frequently components of corrosion inhibitor blends. Other compounds that have been used include nitrogen heterocyclics, substituted thioureas, thiophenols, and alpha-aminoalkyl thioethers (148). 

An efficient synthesis of rigid tricyclic (5 5 5) nitrogen heterocycles 64 has been achieved via sequential and tandem Ugi/intramolecular Diels-Alder (IMDA) cycloaddition of pyrrole derivatives <2004JOC1207> and the trienes 477 were prepared by the acylaton of amines 475 with the anhydride 476. The amines 475 were in turn prepared starting from pyrrole-2-carbaldehyde. The triene 477 on heating in toluene at 80 °C for 15 h underwent the IMDA to afford the tricyclic compound 64 as a single diastereomer in quantitative yield. The sterically bulky N-substitutent on the triene 477 promoted cycloaddition under milder condition at 65 °C in toluene to provide the tricyclic compound 64 in quantitative yield (Scheme 108). 

Both approaches include the reaction of BENA with ternary amines or the -C=N-C-fragment of a nitrogen heterocycle (Nu) in the presence of a silylating agent (Me3SiX). 

A second method of producing pyrazole-containing compounds was described by Olivera et al. [51] and involves the use of an enaminoketone (41) (Scheme 5). The initial amine-exchange/heterocyclization produced pyrazole tautomers, so another method was attempted with NT NHMe. However, two isomers were produced with the methyl group on either nitrogen. Compound 42 was formed in 55% yield. 

In addition to alkenes and alkynes, allenes have attracted considerable interest due to their unique reactivity and multireaction sites. Therefore, transition-metal-catalyzed nucleophilic addition reaction of amines and imines to allenes has been extensively studied to prepare biologically important amines and nitrogen-heterocycles.31,31d... 

Nitrogen heterocycles can also be prepared by the RCM of unsaturated amines having a diphenyl thioacetal moiety (Table 14.3) [31]. 

At that time, as now, the enantiomers of many chiral amines were obtained as natural products or by synthesis from naturally occurring amines, a-amino acids and alkaloids, while others were only prepared by introduction of an amino group by appropriate reactions into substances from the chiral pool carbohydrates, hydroxy acids, terpenes and alkaloids. In this connection, a recent review10 outlines the preparation of chiral aziridines from enantiomerically pure starting materials from natural or synthetic sources and the use of these aziridines in stereoselective transformations. Another report11 gives the use of the enantiomers of the a-amino acid esters for the asymmetric synthesis of nitrogen heterocyclic compounds. 

In any event, 02SbFg and 02AsFg act as very effective one-electron oxidants with regard to aromatic amines, nitrogen- and sulfur-containing heterocyclic compounds (Dinnocenzo and Banach 1986, 1988,1989) as well as to perfluorobenzene, benzotrifiuoride, and perfluoronaphthalene (Richardson et al. 1986). The oxidation proceeds in Freon (CHCIF2) at temperatures from -115 to -145°C, and the formation of the organic cation-radicals has been firmly established. 

Moore and Willer reported the synthesis of some nitramine explosives containing a furazan ring fused to a piperazine ring. The tetranitramine (46) is synthesized from the condensation of 3,4-diaminofurazan (DAF) (24) with glyoxal under acidic conditions followed by A-nitration of the resulting heterocycle (45). The calculated performance for the tetranitramine (46) is very high but the compound proves to be unstable at room temperature. Instability is a common feature of heterocyclic nitramines derived from the nitration of aminal nitrogens. 

Let us consider just one more nitrogen heterocycle here, and that is imidazole, a component of the amino acid histidine (see Box 11.6). The imidazolium cation has pATa 7.0, making imidazole less basic than a simple amine, but more basic than pyridine. Imidazole has two nitrogen atoms in its aromatic ring system. One of these nitrogens contributes its lone... 

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