Ritter products

Itiswer The n-propyl group had best come from an amide (13) which could be the Ritter product if EtCM is used. Making (13) by more conventional methods Is fine, too. 

Cyclic imines are obtained in the related transformation of methylenecyclpropanes with nitriles mediated by triflic acid700 (Scheme 5.68). The reaction pathway suggested to interpret product formation is similar to that in Scheme 5.67. The reaction of intermediate 162 with water may give Ritter products (carboxamides) isolated in some cases. 

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). ... 

Benzylic compounds, such as ethylbenzene, react with alkyl nitriles, ceric ammonium nitrate, and a catalytic amount of Al-hydroxysuccinimide to give the Ritter product, the amide. ° °... 

Evidence supporting the involvement of nitrilium ion intermediates is available from the large number of heterocyclic derivatives obtained by intramolecular trapping reactions. Furthermore, independently generated nitrilium salts undergo hydrolysis to Ritter products (Scheme 3). 

Conversion of 3-cyano-4-stilbazole (69) into a tetrahydrocopyiine derivative illustrates the use of an alkenic group as the cation precursor (Scheme 35). Such processes are frequently less clear-cut for example, reaction of either the unsaturated nitrile (70) or oxime (71) resulted in competitive cycliza-tions to the minor Ritter product (72) and the major Hoesch product (73 Scheme 36). Similar competing processes have been observed for spirocyclohexanone oximes, but in other cases no cyclic products were produced at all. ... 

Olah et al. reported the triflic acid-catalyzed isobutene-iso-butylene alkylation, modified with trifluoroacetic acid (TFA) or water. They found that the best alkylation conditions were at an acid strength of about//q = —10.7, giving a calculated research octane number (RON) of 89.1 (TfOH/TFA) and91.3 (TfOH/HaO). Triflic acid-modified zeohtes can be used for the gas phase synthesis of methyl tert-butyl ether (MTBE), and the mechanism of activity enhancement by triflic acid modification appears to be related to the formation of extra-lattice Al rather than the direct presence of triflic acid. A thermally stable solid catalyst prepared from amorphous silica gel and triflic acid has also been reported. The obtained material was found to be an active catalyst in the alkylation of isobutylene with n-butenes to yield high-octane gasoline components. A similar study has been carried out with triflic acid-functionalized mesoporous Zr-TMS catalysts. Triflic acid-catalyzed carbonylation, direct coupling reactions, and formylation of toluene have also been reported. Tritlic acid also promotes transalkylation and adaman-tylation of arenes in ionic liquids. Triflic acid-mediated reactions of methylenecyclopropanes with nitriles have also been investigated to provide [3 + 2] cycloaddition products as well as Ritter products. Tritlic acid also catalyzes cyclization of unsaturated alcohols to cyclic ethers. ... 

Indeed, Pougny and Sinay had shown that Ritter products could be captured by an in situ carboxylic acid [77]. In keeping with this precedent (Scheme 10a) the glucoside 59 was treated with NBS in very dry acetonitrile, and the Ritter intermediate 60 was captured by the in situ aspartic acid 61 [78], leading to the rearranged a-imide 62a. In view of the three acyl residues, it took several experiments before finding that smooth Af-deacylation could be effected by piperidine to give 62b [79]. 

The Ritter reaction is especially valuable for the synthesis of 3° alkanamines. In fact, there are few alternative routes to them. This reaction is illustrated by the first step in the following sequence. In the second step, the Ritter product is hydrolyzed to the amine. 

Since they are difficult to form, bridgehead cations are highly reactive. Irradiation of hahdes 8 in a variety of media provided a convenient means of exploring the remarkable reactivity of the 1-norbornyl cation (18). It was efficiently trapped by diethyl ether and THE to afford the ethers 19 and 20. Even in aqueous THE, a substantial portion of the butenyl ether 20 was obtained. Trapping by t-butyl alcohol afforded some of the ditertiary ether 21 but was accompanied by formation of 1-norbornanol (22) and 2-methylpropene. Cation 18 was trapped by CHjClj to afford chloride 23, and in aqueous CH3CN the Ritter product 24 was formed. It should be noted that radical abstraction from CH2CI2 occurs at H and ionic abstraction at CL... 

Ritter, J.A. and A.D. Ebner, Separation technology R D needs for hydrogen production in the chemical and petrochemical industries, U.S. DOE Office of Industrial Technologies Program Report, December 2005. 

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. 

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