Schotten-Baumann technique

As was mentioned earlier, esterification using aromatic acid chlorides, ArCOCl, is often carried out in the presence of base (the Schotten-Baumann technique, Sec. 20.8). 

Substituted amides of aromatic carboxylic acids or of sulfonic acids are prepared by the Schotten-Baumann technique the acid chloride is added to the amine in the presence of a base, either aqueous sodium hydroxide or pyridine. For example ... 

The Schotten-Baumann technique has often been applied to acylation of amino acids, particularly for benzoylation and for introduction of the benzyl-oxycarbonyl group. 

Steiger572 has given a general prescription for benzoylation of amino acids by the Schotten-Baumann technique, and also a review of the older literature. Individual prescriptions for benzoylation of glycine573 and 6-aminohexanoic acid574 are to be found in Organic Syntheses. 

The solution polymerization is carried out by Schotten-Baumann technique. In this method, the solution of diacid chloride is added dropwise into an ice-cooled solution of a dicarboxylic acid. The reaction is facilitated by using an acid acceptor such as triethylamine. Polymerization takes place instantly on contact of the monomers and is essentially complete within 1 h. The solvents employed can be a single solvent or a mixture of solvents like dichlorometh-ane, chloroform, benzene, and ethyl ether. It was found that the order of addition is very important in obtaining relatively high-molecular-weight polyanhydrides. Addition of... 

In addition to the above method of prepeiration, attempts have been made without success to meike benzoic acid react directly with sucrose. The process which this paper outlines follows the classical Schotten-Baumann technique as illustrated in Figure 2. 

Figure 2. Manufacturing process (Schotten Baumann technique)...

Industrially prepared,sucrose benzoate is a partially esterified sucrose with a degree of substitution of approximately 7.4. Preparation is via the classical Schotten-Baumann technique utilizing two immiscible solvents which results in better yields with increased purity over other techniques. Sucrose benzoate has excellent UV stability, unusual clarity and lack of color, a low solution viscosity, yields films of excellent depth or fullness of gloss and has a broad range of compatibility with numerous resin systems. It is... 

The Schotten-Baumann reaction between dicarboxylic acid dichlorides and diamines can be performed not only in organic solvents, but also, by means of a special experimental technique known as interfacial polycondensation (see Examples 4-5 and 4-11). Both variants have the advantage of short reaction times at low temperature with simple equipment. 

Carbamates are by far the most common type of amine protection used in solid-phase synthesis. Various types of carbamate have been developed that can be cleaved under mild reaction conditions on solid phase. Less well developed, however, are techniques that enable the protection of support-bound amines as carbamates. Protection of amino acids as carbamates (Boc or Fmoc) is usually performed in solution using aqueous base (Schotten-Baumann conditions). These conditions enable the selective protection of amines without simultaneous formation of imides or acylation of hydroxyl groups. Unfortunately, however, Schotten-Baumann conditions are not compatible with insoluble, hydrophobic supports. Other bases and solvents have to be used in order to prepare carbamates on, for example, cross-linked polystyrene, and more side reactions are generally observed than in aqueous solution. 

Another procedure for converting carbonyl chlorides into aldehydes proceeds by way of Reissert compounds.3448 Reissert found that 1-benzoyl-1,2-dihydro-2-quinolinecarbonitrile is formed in very good yield when benzoyl chloride reacts with quinoline in the presence of aqueous potassium cyanide, the technique being that of a Schotten-Baumann reaction the nitrile can then be hydrolysed to benzaldehyde and quinaldic acid by acid. 

Step-growth polymerizations can also be carried out with certain monomers at low temperature by a technique known as interfacial polymerization or interfacial polycondensation Tht reactions (applicable only to fast reactions) are conducted at the interface between two inuniscible liquids. Usually, one of the liquids is water and the other an organic solvent. An example may be a Schotten-Baumann polyamidation reaction. In such an interfacial polymerization, the diamine would be in the aqueous phase and the diacid chloride in the organic phase. The strong reactivity of acid chloride groups with amines allows the reaction to be carried out at room temperature ... 

The Schotten-Baumann [4] reaction can be applied to the preparation of polyamides using bifunctional reagents. Since the reaction is very rapid at room temperature, it can be carried out at low temperatures (a) in solution or (b) by an interfacial polycondensation technique. 

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