Aniline, dimethyl carbonate reactions

Cesium-exchanged zeolite X was used as a solid base catalyst in the Knoevenagel condensation of benzaldehyde or benzyl acetone with ethyl cyanoacetate [121]. The latter reaction is a key step in the synthesis of the fragrance molecule, citronitrile (see Fig. 2.37). However, reactivities were substantially lower than those observed with the more strongly basic hydrotalcite (see earlier). Similarly, Na-Y and Na-Beta catalyzed a variety of Michael additions [122] and K-Y and Cs-X were effective catalysts for the methylation of aniline and phenylaceto-nitrile with dimethyl carbonate or methanol, respectively (Fig. 2.37) [123]. These procedures constitute interesting green alternatives to classical alkylations using methyl halides or dimethyl sulfate in the presence of stoichiometric quantities of conventional bases such as caustic soda. 

Cs-X has also been used to promote the selective O-methylation of phenol with dimethyl carbonate. 2 N-Monomethylaniline was obtained in 93% yield by reacting aniline with dimethyl carbonate over a K-Y catalyst at 180°C (Eqn. 22.46). 3 The reaction of alcohols with chloromethyl ether over Na-Y gave the resulting methoxymethyl ethers in 70%-90% yields (Eqn. 22.47). 4... 

Alkylation of catechol with dimethyl carbonate in the presence of Li0H/Al203 at 553 K gave the monoether with 84% selectivity at 100% conversion. Some 3-methylcate-chol also formed in the process.37 When the reaction of aniline with dimethyl carbonate is carried out in the gas phase with zeolite KY, the reaction was 93.5% selective for A-... 

More recently, Bouwman carried out a detailed study on the carbonylation of nitrobenzene in methanol with palladium bidentate phosphane complexes as catalysts [29-31]. After a careful analysis of the reaction, mixtures revealed that besides the frequently reported reduction products of nitrobenzene [methyl phenyl carbamate (MFC), A, 7/-diphenylurea (DPU), aniline, azobenzene (Azo) and azoxyben-zene (Azoxy)], large quantities of oxidation products of methanol were co-produced (dimethyl carbonate (DMC), dimethyl oxalate (DMO), methyl formate (MF), H2O, and CO). They proposed the Pd-imido species P2Pd = NPh, which is the central key intermediate that can link together all the reduction products of nitrobenzene and all the oxidation products of methanol into one unified mechanistic scheme. 

The central carbon atom is derived from an aromatic aldehyde or a substance capable of generating an aldehyde during the course of the condensation. Malachite green is prepared by heating benzaldehyde under reflux with a slight excess of dimethyl aniline in aqueous acid (Fig. 2). The reaction mass is made alkaline and the excess dimethylaniline is removed by steam distillation. The resulting leuco base is oxidized with freshly prepared lead dioxide to the carbinol base, and the lead is removed by precipitation as the sulfate. Subsequent treatment of the carbinol base with acid produces the dye, which can be isolated as the chloride, the oxalate [2437-29-8] or the zinc chloride double salt [79118-82-4]. 

In the presence of Lewis acids, N-substituted aniline complexes of [Os] also add electrophiles at C4, again at the arene face opposite to that involved in metal coordination. This reaction has been shown to be general for a broader range of Michael acceptors than may be utilized with anisole complexes of [Os]. The N-ethyl aniline complex, for example, adds Michael acceptors and acetals in yields ranging from 53-95 % (Table 13, entries 1-6) [27]. The N,N-dimethyl aniline complex (entries 7-9) also adds Michael acceptors to C4 in moderate to high yields (Table 13) and adds to the <5-carbon of an a,/ ,y,<5-un saturated ester (entry 3). 

On the other hand, the reaction with anisol or dimethyl aniline afford the product 33) or 34), indicating that the reaction takes place on the phenyl carbon. The striking fact is that only the ortho-substituted compound is obtained (regio-specific reaction) (Eqs. (19) and (20)). 

The analogous thioketone already mentioned is obtained in a similar manner from carbon sulphochloride CSCI2, and dimethyl-aniline it may also be obtained by treating the corresponding oxygen ketone with phosphorus sulphide. The two ketones are similar in their reactions [3]. 

Aromatic /-amines can act as carbon nucleophiles in reaction with perfluorinated 1,3,5-triazines. Amines used are 1-methylpyrrole, 1-methylindole, l,8-bis(dimethylamino)naphthalene (proton sponge), A,A-dimethyl- and JV,7V-diethyl-aniline. All the amines reacted at the expected position in the ring except A,7V-diethylaniline which also gave some or//io-product not seen with N,N-dimethylaniline (Equation (8)) <92T7939>. 

The reaction of 3-imino-N,l,3-triphenylprop-l-enamine (14) with dimethyl acetylenedicarboxylate (DMAD) gives the pyridone (15). If the enamine is /8-disubstituted, as in compound (16), then initial attack occurs on the imine nitrogen rather than the enamine carbon. Electrocyclization followed by loss of aniline then yields the pyridine (17) (Scheme 8). ... 

This transformation takes place readily at room temperature and can be carried out quantitatively by stirring the reaction mixture at 50-70 °C under vacuum for several hours. Ethylene is formed as a result of recombination of the carbon that probably forms at the first step of the decomposition. On the other hand, it was found [292, 295, 296] that quaternary methylammonium salts obtained by alkylation of tertiary amines (MiV-dimethyl aniline or triethyl amine) with dimethyl H-phosphonate are quite stable with respect to the above conversion when heated up to 130 °C and 70 °C, respectively. 

The synthetic and kinetic regularities of the amino-Claisen rearrangement were studied for the transformation of 2,5-dimethyl-Af-(pent-3-en-2-yl)aniline." The products are obtained via conversion of a binary r-complex formed by the reaction of N-alkenylaniline hydrochloride with the hydrochloride of the solvent (2,5-dimethylaniline). Spirocyclic oxindoles have been prepared from iodoindoles via a sequential intramolecular Ullmann coupling and Claisen rearrangement." Nucleophilic ort/io-propargylation of aryl sulfoxides has been reported to occur by intermolecular delivery of the nucleophile to sulfur followed by an intramolecular relay to carbon in a... 

Kinetic studies of ternary complex formation have included the reactions of [Fe(CN)6(OH2)] with aniline in aqueous alcohols and with substitutedpyridines in ethylene glycol, of cw-[Co(en)a(OHa)2] + with 1,10-phenanthroline in aqueous ethanol, of [Co(NH3)5(dmso)] + with halides in dimethyl sulphoxide, of mixed complexes of UOa in carbon tetrachloride and in l,2-dichloroethane, " and of VO + with oxine, salicaldoxime, and acetylacetone in benzene. ... 

Demethylation of poly(sulfonium cation) occurs by nucleophile substitution reaction via Sn2 mechanism The demethylation is also classified as a transmethylation to nucleophiles. Using nucleophiles that have a mobile proton such as phenol, aniline and benzoic acid derivatives in the presence of potassium carbonate, demediyladon of poly( sulfonium cation) proceeds efficiently to yield the methylated products of phenol and benzoic acid with 100 % conversion (Scheme 2). In the case of aniline, both N-methyl and M -dimethyl aniline are obtained and methylation of -methyl aniline occurs more easily than aniline because of the higher Lewis basicity. 

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