Addition reactions nitrogen terminator

Since it has been observed that the hydrogen atoms attached to nitrogen in amines were not easily abstractable in free radical reactions (6, 74), it may be assumed that the aldehydic part of the formamide molecule will be more reactive in the photoaddition reactions than the amino function, thus leading to the following addition reaction with terminal olefins,... 

The addition of a-lithiomethoxyallene 144 [55] to benzaldehyde dimethylhydra-zone 145 (Eq. 13.48) leads to a mixture of pyrroline 146 and dihydroazete 147 [56]. The cydization in this case, which takes place in the same operation as the addition to the hydrazone, follows two distinct pathways, with attack of the nitrogen atom taking place at the inner, in addition to the terminal, carbon atom of the allene. A similar reaction of 144 with SAMP-hydrazone 148 (Eq. 13.49) leads to 3-pyrroline 149 in 88% yield and excellent diastereoselectivity [57]. Cleavage of the chiral auxiliary group from 149 takes place in two steps (1, methyl chloroformate 2, Raney nickel, 50 bar, 50 °C) in 74% overall yield. When the addition of 144 to 148 is conducted in diethyl ether, cydization of the adduct does not take place. Surprisingly, the hydrazones of aliphatic aldehydes react with 144 in poor yield in THF, but react quantitatively and diastereoselectively in diethyl ether to give the (uncyclized) allenyl hydrazone products. 

The standard assay contained 100 vaM Tris-HCl (pH 9), 100 mAf KG, 20 mM threonine and/or serine, and the enzyme. After incubation at 37°C for various times, the reaction was terminated by addition of 3 N HQ. The reaction mixture was centrifuged and 250 / L of the supernate was mixed with 250 /iL of o-phenylenediamine solution (10 mg/mL in 3 N HQ). The tubes were tightly capped and heated in a boiling water bath for 30 minutes. The derivatized keto acids were extracted with ethyl acetate. An aliquot of the ethyl acetate layer was dried under nitrogen. The residue was taken up in 1 mL of the running solvent for HPLC Assays were linear for 30 minutes and with amount of protein added. 

The most common addition reaction of azides in general is the 1,3-dipolar cycloaddition to double and triple bonds. These reactions have been reviewed in this series of books as well as elsewhere, primarily by Huisgen and lately by L abbe, and their mechanism has been discussedThe 1,3-dipolar cycloaddition of azides is generally understood as a concerted process in which the terminal nitrogen of the azido group binds to the atom that is more negative in the olefin, if the olefin happens to be electronically unsymmetric. As a consequence of its concerted nature, it is a stereospecific cis addition. 

Colloidal gold and fine copper powder also catalyze diazoalkane polymerizations. The reaction appears to proceed by formation of alkylidene or carbene species that are bound to the surfaces of metals. " The initiations are completed by additions of diazoalkanes to the bound carbenes followed by liberations of nitrogen. Termination may take place by chain transfer, perhaps to a monomer, or to the solvent. " ... 

The nitrogen atoms of the isocyanides ligands CNR in M2(CO)3(CNR)Cp2 ( M = Fe, Ru) has been proved to be very susceptible to alkylation reactions [12]. The cationic products contain the CN(R )R group invariably located in the bridging position. The carbyne character of these ligands has been evidenced from their p-C nucleophilic addition reactions of H" and CN" v/hich may form either bridging or terminal aminocarbene derivatives. The results of our studies, collected in Scheme 3, can be summarized as follows ... 

The important reaction of the carbonyl group with hydroxylamine has been studied to a wide extent, both its kinetics and its mechanism. The free electron pair on the nitrogen of hydroxylamine is added to the sextet of the carbonyl-group carbon atom, and as the reaction is catalyzed by acids, carbonium ion formed on addition of a proton to the carbonyl oxygen plays a role during the reaction. The addition of hydroxylamine follows, and the reaction is terminated by the splitting off of the proton and a molecule of water. Although acids catalyze the oximation reaction, they also have a reverse influence, because protons are also added to hydroxylamine and form an unreactive ammonium cation. Hence, the optimum reaction course is dependent of a proper choice of pH. 

The addition of borane-protected secondary phosphines to terminal alkynes proceeds under microwave-assisted conditions without the addition of a transition metal, base, or radical initiator (Scheme 4.287) [450]. Furthermore, the authors discovered that the addition reaction did not need to be carried out under an atmosphere of nitrogen. The chemistry predominately generated the Z-isomer, although the formation of the fi-isomer was never completely prevented. It was noteworthy that a terminal alkyne containing a primary alcohol was successfully functionalized. Clearly, the... 

Terminal olefins are readily hydroborated but internal olefins require additional reaction time and heating prior to refluxing with propionic acid. Substituents such as active sulfur, chlorine, or nitrogen are not affected by this hydrogenation procedure. 

In the reactions of nucleophilic addition to diacetylene, monoalkylhydrazines behave in two ways (71AKZ743). In an anhydrous medium at 40-50°C, the reaction with methyl- and ethylhydrazines proceeds in such a way that a more nucleophilic disubstituted nitrogen atom attacks the terminal carbon atom of diacetylene to form l-alkyl-3-methylpyrazoles (17), the content of isomeric 1-alkyl-5-methylpyrazoles being 15% according to GLC (71AKZ743 73DIS 77AKZ332). 

Substitution of an additional nitrogen atom onto the three-carbon side chain also serves to suppress tranquilizing activity at the expense of antispasmodic activity. Reaction of phenothia zine with epichlorohydrin by means of sodium hydride gives the epoxide 121. It should be noted that, even if initial attack in this reaction is on the epoxide, the alkoxide ion that would result from this nucleophilic addition can readily displace the adjacent chlorine to give the observed product. Opening of the oxirane with dimethylamine proceeds at the terminal position to afford the amino alcohol, 122. The amino alcohol is then converted to the halide (123). A displacement reaction with dimethylamine gives aminopromazine (124). ... 

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