Amines, activation

MSC undergoes reactions with alcohols, amines, active methylene compounds (in the presence of bases), and aromatic hydrocarbons (in the presence of Friedel-Crafts catalysts) to replace, generally, a hydrogen atom by a methanesulfonyl group (382—401). 

The following are further examples of amides prepared from carboxylic acids/CDI and primary amines activated by magnesium salts (additional examples are reported in ref. [90]) ... 

In contrast, such approaches have been much more developed with proteins, termed silicateins, that have been extracted from some silicified sponges [38]. The success of these approaches probably originates from the fact that the reactivity of these proteins towards silica precursors differs significantly from the processes occurring in diatoms. Whereas silaffins and poly-amines activate silica formation via electrostatic interactions due to the presence of positively-charged ammonium... 

Amine-activated zinc dibutyl dithiocarbamate, accelerator. 

Amine-activated zinc pentamethylene dithiocarbamate, accelerator. 

Fig. 8.22. 2-[(Acyloxy)methyl]benzamides (8.187) as double prodrugs of active amines. Activation is by cyclization-elimination in a two-step sequence, namely hydrolase-catalyzed hydrolysis of the carboxylate moiety followed by an intramolecular nucleophilic substitution with...

Fig. 3 The three most common modes to activate linear Ugi-products for cyclization, especially if the cyclization involves Ugi-reactive groups (e.g., acid, oxo-compound, or amine). Activation is mostly achieved with convertible isonitriles, i.e., activated amides (see text). Other MCRs follow similar concepts. With orthogonal second functionalities for cyclizations such deprotection and/or activation is not required (see below, e.g., RCM or cycloadditions)...

Most of the drug is inactivated either by conjugation with glucuronic acid (principally in the liver) or by reduction to inactive aryl amines. Active chloramphenicol (about 10% of the total dose administered) and its inactive degradation products (about 90% of the total) are eliminated in the urine. A small amount of active drug is excreted into bile and feces. The systemic dosage of chloramphenicol need not be altered in renal insufficiency, but it must be reduced markedly in hepatic failure. Newborns less than a week old and premature infants also clear chloramphenicol less well, and the dosage should be reduced to 25 mg/kg/d. 

Amines, similar to phenols, form hydrogen bonds with polar compounds. Hydrogen bonding decreases the amines activity in reactions with peroxyl radicals. For example,... 

Introducing ortho substituents to provide steric hindrance slows amine activation... 

The acceleration of the initial stage of the epoxy compound polymerization under the action of the TA in the presence of the primary amine is explained by the role of the proton donor of primary proton amine activating the epoxy ring. The initial polymerization rate increases linearly with increasing concentration of the primary amine 46). 

Photoactivation of auric triarylmethanecyanide dyes with amine activator... 

The NPG/MB and the TMBS/MB systems were also directly compared in film-forming compositions (64,65). Triethanolamine (TEOA) was also used as a further example of an amine activator, and tri(ii-butyl)benzylstannane (TBBS) was sometimes used in place of TMBS. Table 5 lists the compositions that were used. 

A variety of low ionization potential species have been demonstrated as effective activators in the patent literature. Rust and co-workers (19,71) reported that phosphines and arsines function in the same manner as amine activators. A photophysical study of the quenching of electron-poor excited singlet states by triphenylphosphine, reported by Weiss (72), supports the idea that phosphines and arsines should be expected to be... 

Aryldiazosulfones, di(arylsulfonyl)diazomethanes, and di(arylsulfonylmethyl)alkylamines were all reported by Delzenne (9b), and the initiation mechanisms were described. The class of di(arylsulfonylmethyl)alkylamines and aminosulfonates were also studied by Braslavsky (74) by flash techniques. That work demonstrated that electron transfer occurs from the amino moiety in analogy to other amine activators. The mechanisms of radical formation in the other two systems studied by Delzenne are more subtle. They will be discussed below. 

The usefulness of 1,3-cyclohexadiene complexes is enhanced by their conversion to stable cationic complexes. The if -cationic complex 102 is prepared as a stable salt by the hydride abstraction from the neutral complex 66 via 101, and its highly regio- and stereoselective reaction with nucleophiles is used for synthetic purposes. Complex 102 reacts with nucleophiles such as amines, active methylenes, alkyl copper or alkoxides at C(l) or C(5) from the uncomplexed exo side. In other words, the nucleophilic attack occurs regioselectively at a dienyl terminus, and stereoselectively anti to Fe(CO)3 to give 103. Hydride abstraction from 103 affords 104, which reacts with a nucleophile to form 105. Decomplexation of 105 produces the 5,6-disubstituted-l,3-cyclohexadiene 106. 

No such enhancement by retinyl acetate was observed when 2-fluoren-amine activation was carried out by rat liver microsomes prepared from S9 (Figure 2). 

Amines — I mines. This reagent can effect dehydrogenation of secondary amines activated by an aryl group or an a,[3-double bond to imines. The rate and the yield are increased by addition of Cl2Ru[P(C6H5),]1 and molecular sieves. In this respect iodosylbenzene differs from /-butyl hydroperoxide, which also effects... 

As shown in the above reaction scheme, the epoxy groups are successively opened by amine active hydrogens [Eqs. (1) and (2)]. 

All reactive functions, apart from epoxide, require a preliminary amine activation step prior to chemical coupling or a reduction after grafting step (aldehyde). The quantities of chemically immobilized ODN are in the same order of magnitude than those grafted during adsorption (less than 1 mg nr2) which let one suppose that the amine functions carried by the bases also react... 

The magnitude of km, the experimentally determined bimolecular rate constant for chemiluminescence, is related to several of the rate constant specified in Fig. 8. The data on the hydrocarbon- or amine-activated chemiluminescence indicated that kJ0 > k ACT. Thus simple analysis of the kinetics yields (33), where Kn is the equilibrium constant for complex... 

The HDN of aliphatic amines (equation 25) is relevant to the HDN of indoles (equation 26), pyridine (equation 27), and quinoline (equation 28) because these heterocycles are first hydrogenated to the aliphatic amines. A general mechanism proposed for the HDN of aliphatic amines is based on metal cluster catalysis of the transalkylation reaction in equation (33) and on metal complex catalyzed exchange of deuterimn for hydrogen in tertiary aliphatic amines (equation 34). There are other examples of amine activation in metal complexes. 

Exxon Chemical Process. The Exxon Chemical process [1092], [1093] was specifically designed for the company s own site in Canada and so far not built for third parties. It uses a proprietary bottom-fired primary reformer furnace and a proprietary hot potash carbon dioxide removal system with a sterically hindered amine activator. Synthesis loop and converter are licensed by Haldor Topsoe A/S. Synthesis is carried out at 140 bar in a Topsoe S-200 converter and total energy consumption is reported to be 29 GJ/t NH3. 

Copper catalysts offer several advantages over protic acids in hydrolysis reactions. They are mild, non-acidic, and can control regioselectivity by chelation. An example of the latter is shown by the hydrolysis of the bis benzyl ester 13. Complexation with the amine activates the adjacent carboxylate selectively to afford 14 as the sole hydrolysis product (Sch. 4) [11]. 

The photoinitiation activity of poly(ABP)/DMA and IBP/DMA, as compared with that found for poly(ABP) and IBP alone, clearly confirms that the presence of amine activates both the systems. 4-[4-(7V,V-dimethylamino)phenyl] butanoate of 4-hydroxy benzophenone (DMABP), the low-molecular-weight structural model of poly(ABP-co-DMAS), having benzophenone and tertiary amine functions in the same molecule, is foimd [18,22,53] to display an intermediate activity with respect to those observed for poly(ABP)/DMA and poly(ABP-co-DMAS) systems (Table 11). 

Chemically, methods for deoxygenation and reductive deamination have seen additions in the last two decades which depart from those traditional approaches using hydride reduction of activated alcohols and diazene generation from aliphatic amines. New methods for amine activation, new complex hydrides and, in particular, methods using electron transfer and free radical processes have greatly expanded the range of substrate molecules which can be subject to efficient functional group removal. 

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