Methanal Acid catalyzed addition

Reactions have been run to make amine-group-containing lignin (121-123) and free, amine groups which can accept a proton have been quantified (118) in the lignin products. The use of amination to form commercial products of lignin requires that beta amino ketones be formed on the aliphatic chains in the polyalkylaromatic. The acid catalyzed addition of methanal and a primary or secondary amine (Mannach reaction 124) is conducted on alkali lignin in aqueous... 

Snider and coworkers125 have reported the Lewis acid catalyzed [2 + 2]cycloaddition of (phenylsulfonyl)allene 112. The reaction with methylenecyclohexane in dichloro-methane gives a 25% yield of an 8 1 mixture of 210 and 211 (equation 132). An addition reaction of l-(p-tolylsulfonyl)ethylene with enamines gives aminocyanobutanes via the zwitterionic intermediate (212) as shown in equation 133126. 

The production of aniline is a major international business, carried on in the US, Europe and Asia, mainly for the conversion, by reaction with formaldehyde under acid-catalyzed conditions, into diaminodiphenylmethanes 9a, 9b and 9c, and then into isocyanates, mainly 4,4/-methylenebis(phenylisocyanate) (MDI, also known as 4,4 -methylene-di-paraphenylene isocyanate, 4,4 -diphenylmethane diisocyanate, methylene diphenylene diisocyanate and diisocyanato diphenyl methane) (9d), from which polyurethanes are produced. This accounts for well over 60% of total demand (Figure 1). Aniline is also used in bulk for the production of antioxidants and vulcanization accelerators for rubber. Some 15.5 million lbs. of cyclohexylamine are made each year mainly by catalytic hydrogenation of aniline. Half the demand is for use as a boiler water additive. Other major uses include in the manufacture of herbicides, plasticizers, emulsifying agents, dyes, dry-cleaning soaps, acid gas absorbents and, in Asia, cyclamate sweeteners. Apart from India, the use of aniline for dyestuff manufacture represents about 10% of demand. 

The present world rcscr es of natural gas that contains mainly methane are still underutilized due to high cost of transportation. Considerable interest is therefore presently shown in the conversion of methane to transportable liquids and feedstocks in addition to its previous sole use for heating purposes by combustion. One possible new route for the utilization of methane derived from natural gas or other sources for conversion to more valuable higher hydrocarbons is the methylation of aromatic hydrocarbons. This chapter provides a general overview of the work that has been done so far on the use of methane for catalytic methylation of model aromatic compounds and for direct liquefaction of coal for the production of liquid hydrocarbons. The review is especially focused on the use of both acidic and basic zeolites in acid-catalyzed and base-catalyzed methylation reactions, respectively. The base-catalyzed methylation reaction covered in this discussion is mainly the oxidative methylation of toluene to produce ethylbenzene and styrene. This reaction has been found to occur over basic sites incorporated into zeolites by chemical modification or by changing the electronegative charge of the zeolite framework. 

In addition, iodine snccessfnlly catalyzed the electrophilic snbstitntion reaction of indoles with aldehydes and ketones to bis(indonyl)methanes [225], the deprotection of aromatic acetates [226], esterifications [227], transesterifications [227], the chemoselective thioacetalization of carbon functions [228], the addition of mercaptans to a,P-nnsatnrated carboxylic acids [229], the imino-Diels-Alder reaction [230], the synthesis of iV-Boc protected amines [231], the preparation of alkynyl sngars from D-glycals [232], the preparation of methyl bisnlfate [233], and the synthesis of P-acetamido ketones from aromatic aldehydes, enolizable ketones or ketoesters and acetonitrile [234],... 

In addition to small amounts of methane, acetaldehyde or acetic anhydride can be generated in substantial quantities depending on conditions. However, they are not present simultaneously in any appreciable quantity. Acetic anhydride and acetaldehyde must be competitively formed (equation 6), and subsequently react with each other to form EDA (step C). This reaction (step C) is generally catalyzed by protic acids (2-4). The reaction solution for reductive carbonylation is quite acidic HI is an intermediate generated under reaction conditions of high alkyl iodide concentration and hydrogen pressure. The thermodynamic equilibrium of this condensation is quite favorable for diester formation existence of an abundance of either anhydride or aldehyde in the presence of the other is not found. Yields of stoichiometric preparations are in excess of 95%... 

In addition to Sen s work on the Rh-catalyzed oxidative carbonylation of methane, Grigoryan has also reported a similar reaction in acetic acid [45]. Predictably, the reaction rate is between that observed in pure water and in the perfluoro-... 

Periana et al. have reported a mercury system that catalyzes the partial oxidation of methane to methanol.81 Hg(II) is typically considered to be a soft electrophile and is known to initiate electrophilic substitution of protons from aromatic substrates. The catalytic reaction employs mercuric triflate in sulfuric acid, and a key step in the catalytic cycle is Hg(II)-mediated methane C—H activation. For methane C—H activation by Hg(II), an oxidative addition reaction pathway via the formation of Hg(IV) is unlikely. Thus, an electrophilic substitution pathway has been proposed, although differentiation between proton transfer to an uncoordinated anion versus intramolecular proton transfer to a coordinated anion (i.e., o-bond metathesis) has not been established. Hg(II)-based methane C H activation was confirmed by the observation of H/D exchange between CH4 and D2S04 (Equation 11.9). 

However, the term pseudo-base has been more widely used to describe compounds which can lose a hydroxyl ion with change of structure, and hence undergo slow reactions with acids, which are reversed by the addition of base. Examples are the carbinol bases of various triphenyl-methane dyes, such as crystal violet, and derivatives of pyrazine and acridine (Hantzsch and Kalb, 134 Aston, 135, 136). However, this kind of change is not strictly analogous to an ordinary acid-base reaction, and it is probably better not to use the term pseudo-base in this connection. In any case, processes involving transfer of hydroxyl ions are not believed to play any important part in catalyzed reactions. 

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