Mannich alkali

For the first time, we have succeeded in preparing a vulcanized waterborne protective crack-resistant coating—based on CSPE for concrete and other substrates—that has better corrosion, crack, gas, and water resistance. These properties have been achieved by the application of a waterborne vulcanizate, which has never been used before. For this purpose, compounds such as Mannich alkalis (MAs) were applied, which cause the formation of quaternary ammonium bonds in a vulcanized net of the saturated elastomer and have reactive functional groups. 

Water dispersions of CSPE emulsion are mixed thoroughly with all composition components excluding Mannich alkalis. 

The second main component (i.e., water solution of Mannich alkalis) was added to the mixture just before applying the coating to the surface of the substrate. 

A new type of anticorrosive and crack-resistant coating that is based on an ecologically safe CSPE dispersion hardened by aqueous solution of Mannich alkalis was developed and investigated. 

Advanced crack-resistant coatings based on water dispersion of chlorine-sulpho-polyethylene (CSPE, Hypalon ) vulcanized by a Mannich alkali (MA) water solution were obtained. Application of MA as a CSPE structure component makes it possible to produce a vulcanized net of saturated polymer, and thus to develop an ecologically safe, impenetrable crack-resistant coating for any substrata (concrete, metal, plastic, etc.). The coatings can be applied in the aircraft, automotive, shipbuilding, paint, and varnish industries, civil engineering, and so on as a corrosion-resistant material. The optimal coating composition and its mechanical properties have been studied. 

Synthetic routes to a-nitroalkenes have been discussed in previous sections. General routes include (1) treating /3-nitroacetates with alkali metal acetates, carbonates or bicarbonates, (2) elimination of water from /3-nitroalcohols via heating with phthalic anhydride or in the presence of a base," ° and (3) degradation of the Mannich products derived from a primary nitroalkane, formaldehyde, and a secondary amine. ... 

Peptide thioesters (Section 15.1.10) are generally prepared by coupling protected amino acids or peptides with thiols and are used for enzymatic hydrolysis. Peptide dithioesters, used to study the structures of endothiopeptides (Section 15.1.11), may be prepared by the reaction of peptide nitriles with thiols followed by thiolysis (Pinner reaction). Peptide vinyl sulfones (Section 15.1.12), inhibitors of various cysteine proteases, are prepared from N-protected C-terminal aldehydes with sulfonylphosphonates. Peptide nitriles (Section 15.1.13) prepared by dehydration of peptide amides, acylation of a-amino nitriles, or the reaction of Mannich adducts with alkali cyanides, are relatively weak inhibitors of serine proteases. 

Mannich bases (26 R2 = CH2NR3R4) are dealkylated in acid or in alkali to the corresponding oxadiazolines (25). 

The degradation with alkali, following the reaction path outlined earlier (part-structures LVIIb LVIIIa— -b- c) would result in the formation of the aldehyde LXVI. The production of this compound can be explained very convincingly by reverse Mannich decomposition of apopseudoakuammigine to the intermediate zwitter ion LXIII. The alternative conformation of this molecule is one (LXV) in which the C-17 hydrogen is situated in close proximity to the trigonal C-3 hydride transfer, as postulated by Joule and Smith, would then be expected to... 

Mannich condensation, 166 Mannitol, effect of alkali tetraborates on rotation of, 36... 

For example, an effective procedure for the synthesis of LLB (where LL = lanthanum and lithium) is treatment of LaCls 7H2O with 2.7 mol equiv. BINOL dilithium salt, and NaO-t-Bu (0.3 mol equiv.) in THF at 50 °C for 50 h. Another efficient procedure for the preparation of LLB starts from La(0-/-Pr)3 [54], the exposure of which to 3 mol equiv. BINOL in THF is followed by addition of butyllithium (3 mol equiv.) at 0 C. It is worthy of note that heterobimetallic asymmetric complexes which include LLB are stable in organic solvents such as THF, CH2CI2 and toluene which contain small amounts of water, and are also insensitive to oxygen. These heterobimetallic complexes can, by choice of suitable rare earth and alkali metals, be used to promote a variety of efficient asymmetric reactions, for example nitroaldol, aldol, Michael, nitro-Mannich-type, hydrophosphonylation, hydrophosphination, protonation and Diels-Alder reactions. A catalytic asymmetric nitroaldol reaction, a direct catalytic asymmetric aldol reaction, and a catalytic asymmetric nitro-Mannich-type reaction are discussed in detail below. 

Bases Vtl are soluble in water and split CHjO througii the action of alkalis, contrary to Mannich bases which are insoluble in water and stable towards alkalis. 

By analogy with (37) <84KGS1219> and (38) <83KGS1086>, the )S-positions in dihydrobenzo[2,l-b 3,4-Z> ]dipyrrole (39) are the sites where electrophilic substitutions occur. The benzodipyrrole (39) afforded, upon treatment with dimethylamine hydrochloride and formaldehyde in methanol followed by addition of alkali, the Mannich bis-base (293) (Equation (2)). Benzodipyrrole (39) has been claimed to behave towards electrophilic reagents as a double indole rather than an a,a -bipyrryl <87CC1176>. 

The Robinson annulation is the reaction of alkali metal derivatives of cyclohexanones with a-,p>unsaturated methyl ketones to produce cycloketones and polycycloketones. The standard method for Robinson annulation is exemplified in the mechanism shown above. For the synthesis of the 1,5-diketone side chain, the enolate nucleophile reacts with a Michael acceptor this Michael acceptor is usually a substituted vinyl ketone or the parent methyl vinyl ketone (MVK), although the latter gives low yield due to its propensity to polymerize under the standard reaction conditions. To overcome the drawbacks for using MVK, Robinson, McQuillin and Du Feu introduced the Robinson-Mannich variation of the annulation reaction. This modification uses a quatemized Mannich base formed from the vinyl entity the Maimich base is made in situ and acts as a methyl vinyl ketone precursor after it is converted to its methiodides. The formed methiodides of the Mannich adduct 4-(trimethylamino-2-butanone) is condensed with sodioderivatives of ketones or with the parent ketone in the presence of sodium ethoxide. 

Aminomethylated compounds (eqs. (15.13) and (15.16), Scheme 15.1) obtained by the Mannich reaction yield various kinds of 2-metalated compounds. The aminomethylated compounds yield quaternary amine salts by the Menshutkin reaction with an alkyl halide, and a methylol derivative is prepared by adding alkali to the salt. Dihydrocholesterol (cholestanol) reacts with dimethylamino-methylferrocene in the presence of methyl iodide and acetone to afford the ferrocene derivatives as shown in Scheme 15.5 [76,77],... 

The lanthanide-alkali metal heterobimetallic complexes have also been shown to promote other reactions, such as nitro-Mannich (aza-Henry) reaction [154],... 

Hydroxypyridine, in the Mannich reaction, gives 2-dialkylamino-methyl-3-hydroxypyridines, and 5-hydroxy-2-methylpyridine is substituted at In contrast, 2-hydroxypyridine, with formaldehyde and alkali,... 

The actual catalyst in phosphoric acid-catalyzed Mannich-type reaction of imines with 1,3-dicarbonyl compounds is certainly phosphoric acid itself [74], but metal contaminants, such as alkali or alkaline-earth metals, have interesting effects on the reactivity and stereoselectivity. HCl-washed, metal-free chiral phosphoric acid 149a and chiral calcium phosphate 149b are able to catalyze the Mannich-type reactions. The absolute stereoselectivity of the phosphoric acid catalysis is opposite that of the calcium phosphate catalysis (Scheme 28.16) [75]. 

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