Ritter reaction solvents

A transannular solvent participation has instead been observed in the IN3 addition in CH3CN to tricyclo[4.2.2.02-5]deca-3,7-diene derivatives 62 and 63, which give adducts 64 and 65 as well as tetrazoles 66 and 67 via Hassner-Ritter reaction (equation 69). 

The formation of the tetrazoles 66 and 67 from 62 and 63, respectively, has been rationalized on the basis of the solvent-assisted opening of the initially formed iodonium ion to give the Ritter reaction intermediate 68, which undergoes cycloaddition with azide... 

The I2 addition to 3 in chlorinated solvents yields a mixture of isomeric 2,6-diiodobicy-clo[3.3.0]octanes (endo.exo-69 and endo,endo-7tt) (equation 71)22. When the reaction was carried out in aqueous acetonitrile under similar conditions, the formation of a mixture of acetamido derivatives 71 and 72, arising from iodocyclization followed by the capture of the iodonium ion by the solvent to give a Ritter reaction intermediate, accompanied the formation of products 69 and 70 (equation 72)22. 

Ionic hydrogenation of the same bicyclic diene 382 by Et3SiH in the presence of CF3COOH at room temperature or at 80 °C via ions 387 and 388 is accompanied by transannular cyclizations (equation 139)192. The behavior of diene 382 under Ritter reaction conditions (MeCN, H2SO4) reveals new possibilities to control the transannular cyclizations (equation 140)193. Depending on the sulfuric acid concentration, the reaction temperature and the presence of a nucleophilic solvent, these transformations can be directed to the formation of either the bicyclic amides 389 and 390 having the precursor structure or the tricyclic products 391193. 

Several procedures have been reported using acetonitrile as solvent for Bi(III) salt-catalyzed transformations involving epoxides as substrates [54, 93-95]. However, no reference has been made about the occurrence of the Ritter reaction, even... 

Br prevents side reactions and makes BiBr3 a better Lewis acid catalyst, which is in accordance with our work BiBr3 affords only Ritter reaction products in the high dielectric constant solvent CH3CN, while BiCl3 originates a mixture of both v7 -/V-acylamino-hydroxy compounds and chlorohydrins. 

With alkanenitriles179 or benzonitrile196,197 as solvents, electrophilic arylations of the nitrogen atom occur and, V-arylamides are formed (Ritter reaction) together with the expected fluorinated compounds. 

The acid used in the Ritter reaction is usually sulfuric acid, although other acids such as perchloric, phosphoric, polyphosphoric, formic and sulfonic acids have been used. Lewis acids such as aluminum trichloride and boron trifluoride are also occasionally used. However, high yields are generally best obtained with sulfuric acid. The choice of solvents varies among sulfuric acid, glacial acetic acid, acetic an-... 

If the reactions are carried out in a nitrile as solvent, rather than dichloromethane, using triflic acid as catalyst, a modified Ritter reaction takes place, and the intermediate nitrilium ion traps the liberated amine, forming an amidine (Scheme 67). In an earlier reaction cf. Scheme 67) the lithium perchlorate catalyzed reaction of sulfenyl chlorides with alkenes in the presence of nitriles had also given l-amido-2-sulfenyl adducts. Ritter products are also obtained in good yields by anodic oxidation (Pt or C, 1.2-1.4 V) of disulfides in acetonitrile, in the presence of excess alkene, using B114NBF4 as supporting electrolyte (Scheme 68). ... 

To favor the coupling reaction, the competing side reaction of the radical cation with nucleophiles must be suppressed by the use of a medium of low nucleophilicity. The solvent of choice is dichloromethane. Especially in electroanalytic studies, neutral alumina is frequently added to suppress hydroxylation of the radical cation [20]. The reversible cyclic voltammetric behavior of radical cations is also enhanced in mixtures of methylene dichloride, trifluoroacetic acid, and trifluoroacetic anhydride (TFAn) with TBABF4 as supporting electrolyte. With acetonitrile as solvent, acetamides, formed in a Ritter reaction, are often the major products. The selective dimerization of mesitylene in acetonitrile is exceptional (Table 1, number 3). Dichloromethane, however, is reducible at the cathode. 

An efficient synthesis of amides by the Ritter reaction of alcohols and nitriles under MW irradiation was developed under solvent-free conditions (Scheme 8.36). This green protocol is catalyzed by solid-supported Nafion NR50 with improved efficiency and reduced waste production." ... 

If the nitration of olefins by nitronium salts is carried out in acetonitrile, the nitrocarbenium ion intermediates undergo Ritter reaction with the solvent to form nitroacetamides [87]. 

No attempt was made to optimise the yield of any one product but it was noted that the product composition was highly dependent on the reaction variables. The mechanism is similar to that of the Ritter reaction in which an olefin reacts with a nitrile and a nucleophOe in a sulphuric acid medium but in this case HCN is the nitrile and the products obtained are quite different. Compound (37) is stable in the absence of protic solvents and reacts with HCN or sodium cyanide to give di-t-octylamino-maleonitrile (40). The latter is oxidised by benzoyl peroxide to give di-t-octyliminosuccinonitrile (41). 

Recently, Rapolu et al. (2013) synthesized primary amides by the Ritter reaction of secondary and tertiary alcohols with nitriles catalyzed by SSA catalyst in toluene at 90°C (Scheme 5.55). As the catalyst is cost-effective, stable to air, and recyclable, the present method constitutes a noteworthy modification to the Ritter reaction for the synthesis of amides. Under these conditions, a variety of amines including sterically hindered amines were successfully reacted to form the corresponding amides in excellent yields. The reaction was observed to be chemoselective in nature. Mirjalilia and Sadeghi (2009) studied the Ritter reaction under solvent-free conditions (Scheme 5.56). 

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