Schotten - Bauman reaction

The 1,3-diester derivative of 2-imino-4-thiazoline (369) is obtained by the Schotten-Bauman reaction (Scheme 213) (263). 

Schiff bases, 256-259, 268, 270 to amines. 40 from aminothiazoles, 98 with 2-amino thiazoles, 30, 40 complexes of, 99 cyclization to, 42 IR spectra of, 41 in reduction by AlLiH,. 14 in reduction by NaBH4, 14 LTV spectra of, 41 see also Thiazolylamidines Schistosomacidal, 141 Schistosomiasis japonica, 145 Schotten-Bauman reaction. 51. 123 Sedative, 145. 148,438 Selective herbicide, 135 Self association, effect of, on UV spectra of A-4-thiazoline-2-thione. 381 A-4-thiazoline-2-one, relation with protomery, 377... 

The first of these procedures is the well-known Schotten-Bauman reaction [403-408] in which an AA monomer such as di(add chloride) is allowed to react, in the presence of an organic base, with a BB monomer such as aromatic diamine to form a polymer. 

Benzoate plasticizers have been recognized since the 1940s as useful plasticizers for PVC. It was not until the mid-1950s, however, that benzoates useful in vinyl compositions were specifically identified and commercialized. Benzoate esters can be produced by direct esterification, transesterifleation, via the acid chloride route, or Schotten-Bauman reaction. The current preferred method for most benzoate esters... 

By far the most common method for preparation of amides is the reaction of ammonia or a primary or secondary amine with one of the reactive reagents described in Section 3.4.1. When acyl halides are used, some provision for neutralizing the hydrogen halide is necessary, because it will otherwise react with the reagent amine to form the corresponding salt. Acid anhydrides give rapid acylation of most amines and are convenient if available. The Schotten-Bauman conditions, which involve shaking an amine with excess anhydride or acyl chloride and an alkaline aqueous solution, provide a very satisfactory method for preparation of simple amides. 

Several attempts to prepare typical alcohol derivatives of [Cr(HO-A)2]-were unsuccessful these include Schotten-Bauman conditions (acetyl chloride in chloroform shaken with cold, aqueous alkaline solution of complex), refluxing in acetyl chloride, in glacial acetic acid, acetyl chloride in hot dimethyl formamide, acetyl chloride and pyridine in acetonitrile, and acetic anhydride in acetonitrile. The failure of refluxing acetyl chloride to effect acetylation brings to mind the work of Keller and Edwards (4) the acetyl chloride system is completely heterogeneous and consequently not conducive to reaction. However, even the homogeneous reaction of [Cr(HO-A)2] — with acetyl chloride in acetonitrile failed to give a measurable quantity of the diester. 

Reaction of L-glutamic acid with /7-nitrobenzoyl chloride under Schotten-Bauman conditions gave (29), from which the diester (30) was obtained using refluxing 5 % ethanolic HC1. Catalytic reduction of the nitro group then yielded (31) [48] Scheme 3.4). 

The Schotten-Bauman condensation produces polyanhydrides with moderate molecular weights by a dehydrochlorination reaction between a diacid chloride and a dicarboxylic acid. The polymerization takes place by reacting the monomers for 1 hr at room temperature, and it can be conducted via solution or interfacial methods. Solvents that are used in solution polymerization include dichloromethane, chloroform, benzene, and ethyl ether. The degree of polymerization obtained with this method is approximately 20-30. Lower molecular weight products are obtained for less reactive monomers such as isophthaloyl chloride. 

In one synthetic approach (Veld 1990, 1992), alanine is first converted to the bromo derivative via the reaction of the diazonium salt of the amine with hydrogen bromide. In the next step the acid functionality is activated by converting it to the acid chloride using thionyl chloride. The activated acid is condensed with a protected a-amino acid to yield the dipeptide intermediate which is then cyclized by heating in presence of Celite (ion exchange resin) to yield the final product. However, the overall yield of this reaction is fairly low. A more elegant approach is shown in Scheme 5. In this approach, an a-amino acid wth a protected side chain (e.g., e-Z-lysine) is reacted with 2-bromo-propionyl bromide under Schotten-Bauman condidons (Fischer 1908) to yield the intermediate 5a, which is then cyclized under basic conditions to the depsipeptide 5b. 

PhCOCl reacts also easily with primary or secondary amines in the presence of a base, aqueous alkali (Schotten-Bauman procedure), or tertiary amines (pyridine or EtaN), to afford the corresponding amides (eq 28). This reaction is used to protect... 

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