Catalysts reactions with amines

Several studies were performed in order to establish the mechaiusm (5-7). The currently accepted mechartism, presented in Scheme 26.1 for the Pd(BINAP) catalyzed amination, involves the formation of a complex, Pd(BINAP)2 from a catalyst precursor (usually Pd(OAc)2 or Pd2(dba)3) and ligand this complex lies outside the catalytic cycle and undertakes dissociation of one BINAP to form Pd(BINAP) the following steps are the oxidative addition of the aryl halide to the Pd(BINAP), reaction with amine and base, and the reductive elimination of the product to reform Pd(BlNAP). 

In some of Forlani s works, such as the reactions of l-halogeno-2,4,6-trinitrobenzene with 2-hydroxypyridine123,125, a substrate-catalyst molecular complex was assumed, but the kinetic law showed the regular second order in amine. Rather interestingly in this scheme, the authors assume that the molecular complex can lead to the formation of products following a second order in nucleophile kinetics, while in the reactions with amines it was presumed that the complex was not on the reaction coordinate, and that an additional molecule of amine was required (the authors needed to include this additional molecule to account for the third order in amine rate law). 

Symmetrical carbodiimides, i.e., molecules with the same substituent on both nitrogen atoms, are best prepared from alkyl or aryl isocyanates in the presence of a phospholene oxide catalyst, the byproduct being carbon dioxide gas. No solvent is required for this reaction. Unsymmetrical carbodiimides or alkylarylcarbodiimides are also obtained from isocyanates, either by reaction with amines and subsequent dehydration of the intermediate... 

Although there are reports that nitric oxide can form nitrosamines by a direct reaction with amines (Drago et al., 1961), it now appears unlikely that nitric oxide itself is the effective nitrosating agent. Since the presence of small quantities of air or other catalysts is required, it would appear that nitrogen dioxide and other species bring about the reaction (Challis and Kyrtopoulos,... 

The partially epoxidized compound was shown to have an average of two epoxy groups per cube. Both polyepoxides readily polymerized in the presence of Lewis acid catalysts or in reaction with amines. This suggested their potential as coupling agents in the synthesis of novel inorganic-organic hybrids. 

The pattern of base catalysis of reactions with amine nucleophiles provides additional evidence. These reactions are catalyzed by bases only when a relatively poor leaving group (e.g., OR) is present (not Cl or Br) and only when relatively bulky amines are nucleophiles. Bases could not catalyze step 1, but if amines are nucleophiles, bases can catalyze step 2. Base catalysis is found precisely in those cases where the amine moiety cleaves easily but X does not, so that k i is large and step 2 is rate determining. This is evidence for the S Ar mechanism because it implies two steps. Furthermore, in cases where bases are catalysts, they catalyze only at... 

The telomerization reaction is carried out using the catalyst modified with amine-containing phosphines, then hydrochloric acid is introduced into the above reaction mixture. As a result phosphine is changed to the hydrochloric acid salt of the amine, so the modified catalyst is dissolved in water. The catalyst can be re-used after treatment with an alkaline solution [2]. 

P(NB/MA) proved to be surprisingly resistant to hydrolysis, both in solution and as a thin film(2. Moreover, the diacid prepared by hydrolysis in concentrated TMAH reverts to the anhydride upon heating(2ri). Similarly, alcoholysis with methanol is difficult and the methyl half-ester reverts to the anhydride on heating(2ri). Reactions with amines to yield poly(amic acids) and poly(imides) proceed more readily. However polyimides are too strongly absoibing at 193 nm to make suitable resist matrices. Also, because primaiy amines are potent imidization catalysts for amic adds(P), amidization of P(1 /MA) with these also causes strong absoibance at 193 nm. Selective amidization can be achieved with buU secondary amines which yield stable poly(amic add) with aqueous base solubility and acceptable transparency (absorbance = ca 0.5 AU/pm at 193 nm). These materials... 

Trichloromethyl ketones (154) undergo smooth transfer hydrogenation in up to 98% ee, using a chiral ruthenium catalyst, to give the corresponding alcohol (155) in up to 97% yield. " Subsequent Jocic-type reaction with amines, again under mild conditions, 0 gives chiral amino-amides (156). 

The catalysis of isocyanate reactions has been extensively studied because of its critical importance in many of these processes. Noncatalyzed (or rather, self-catalyzed) reactions may sometimes be fast enough in practice isocyanate reactions with amines are so fast that only recent studies using stopped-flow methods could lead to useful data [255, 256], metallic or tertiary amine catalysts being ineffective in this case. 

An early example of chiral alcohol-based hydrogen bonding catalysts is the work by Braddock and coworkers in which they used paracydophanediols (PHANOLs) as dual H-bond donors [65, 66]. Significant rate enhancements were obtained in the Diels-Alder reactions of dienes with a,P-unsaturated aldehydes and ketones and in the epoxide-opening reactions with amines. However, little or no asymmetric induction was obtained when a chiral PHANOL catalyst was used. 

The reaction with amine derivatives such as 4-hydroxybenzeneamine 20 and 4,4 -methylenebis-benzeneamine 22 is used to produce the tri- and telrafunctional epoxies N,N,0-tris(2,3-epoxypropyl)-4-hydroxybenzeneamine 21 and A,A,iV, iV -telrakis (2,3-epoxypropyl)-4,4 -methylenebisbenzeneamine 23, respectively. However, the polyfunctional epoxies that combine the most attractive properties for electronic applications are the resins produced by epoxi-dation of the phenol novolac 24 and cresol novolac 26. Novolac resins are obtained by the condensation of a phenol with formaldehyde in the presence of acid catalysts in such conditions that the degree of polycondensation is in the range of 3—5. The epoxy novolacs 25 and 26 are produced by the reaction of epichlorhydrin with the corresponding phenol novolac and ortho-cresol novolac resins. Epoxy resins are generally characterized by their dynamic viscosity (77) at 25 °C, expressed in millipascal second (mPa s). 

---