Schmidt reaction, nitriles from

Nitrilium salts, e.g., 66, prepared from the alkylation of nitriles, react with sodium azide to yield 1,5-disubstituted tetrazoles, e.g., 67 (Scheme 7).121 The Schmidt reaction,122 a versatile method for the preparation of 1,5-disubstituted tetrazoles from ketones and hydrazoic acid, can now be regarded as a special case of azide addition to nitrilium salts.123... 

The participation of nitrilium salts has also been postulated42 in the Schmidt reaction and in some Beckmann rearrangements when concentrated sulfuric acid is employed. Hill43 has demonstrated recently that some Beckmann rearrangements carried out in a concentrated sulfuric acid medium are Ritter-type reactions in which the nitrile formed in situ from the oxime combines with a carbonium ion to yield a nitrilium salt, which, when diluted with water, leads to the N-alkylamide. 

This method provides easy access to 4-alkylbenzoyl chlorides, which are useful intermediates in the preparation of diaryl esters that have mesomorphic properties.20 Benzoyl chlorides substituted in the 4-position also serve as starting materials for the preparation of aromatic aldehydes21 and nitriles,622 whereas the acids, derivable quantitatively from the acid chlorides, are good precursors via the Schmidt reaction to 4-substituted anilines.23... 

Schmidt Reaction.54 Closely related to the Curtins reaction in its mechanism is the Schmidt reaction, whereby carbonyl compounds react with hydrazoic acid in acid solution to give rearranged products. Amines, amides, nitriles, and tetrazoles are the most common substances obtained from the reaction. 

The authors proposed a radical mechanism (Scheme 4.26). Initially TMSN3 is oxidized by PIDA to give azide radical. Then it grabs a hydrogen atom from the methyl group of 11 through SET process to form the delocalized radical A, which is then oxidized to cation B. This species could be stabilized in zwitterions form. B is then trapped by azide anion to give 23. The species D is then formed by 23 from a consecutive SET process via C. Einally, D produces nitrile 12 from a Schmidt reaction. 

Rokade BV, Prabhu JR (2012) Chemoselective Schmidt reaction mediated by triflic acid selective synthesis of nitriles from aldehydes. J Org Chem 77(12) 5364-5370 Nimnual P, Tummatorn J, Thongsornkleeb C, Ruchirawat S (2015) Utility of nitrogen extmsion of azido complexes for the synthesis of nitriles, benzoxazoles, and benzisoxazoles. J Org Chem 80(17) 8657-8667... 

The reactions of HN3 with cyclic alcohols to yield mixtures of ketones, amines, and products with an enlarged ring are catalyzed by H2SO4 [1]. Tertiary alcohols are converted to azides in the presence of acid [12] or TiCU [13]. Aldehydes and ketones with HN3 undergo a Schmidt-type reaction by liberating N2 and inserting NH In the presence of H or Lewis acids [14]. Ketones yield secondary amides and, in the case of cyclic ketones, lactames. Aldehydes are converted to nitriles or N-formylamines. Tetrazole derivatives result with excess HN3 [1, 15]. However, a-azido ethers are obtained from aldehydes and HN3 in the presence of alcohols by catalysis of TiC [16]. Carboxylic acids and anhydrides form amines, N2, and CO2 in Schmidt reactions with HN3. Intermediates are carbamic acids which form by insertion of NH into the R-COOH bond [1, 14]. High yields result for acids of arenes [17]. 

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