Baumann-Schotten reaction

Esterification or amidation of acid chloride with alcohol or amine under basic conditions. 

heteroaryi R = aikyi, aryi X = F, Ci, Br, OCOR inorganic base NaOH, KOH, Na2C03, NaHC03 organic base pyridine, DMAP, Et3N, ( -Pr)2NEt, PPhs Lewis acid MgBr2, Sc(OTf)3, Yb(OTf)3, TMSOTf 

Mechanism of ester formation in the presence of pyridine (nucieophiiic cataiyst)  

The first enantioselective total synthesis of (-)-tejedine was completed by P.E. Georghiou using a chiral auxiliary-assisted diastereoselective Bischler-Napieralsid cycHzation as one of the key steps.The chiral auxiliary was the commercially available (S)-a-methylbenzylamine, which was coupled to the substrate using the original Schotten-Baumann acylation conditions. The acid chloride was reacted with the chiral amine in a solvent mixture containing aqueous sodium hydroxide and dichloromethane and the desired amide was isolated in excellent yield. 

The first asymmetric synthesis of (+)-cannabisativine was achived by D.L. Comins et al. using the addition of metallo enolates to a chiral 1-acylpyridinium salt as one of the key steps.The amide bond was created under the Schotten-Baumann conditions from a bicyclic acid chloride and a 1,4-amino alcohol. 

---

Thus phenol when subjected to the Schotten Baumann reaction first dissolves in the sodium hydroxide to give sodium phenoxide, which then undergoes CgH COCl + NaOCgH, CgHaCOOCeHj XaCl... 

When these benzoyl compounds separate in the course of the Schotten-Baumann reaction, they frequently occlude traces of unchanged benzoyl chloride, which thus escapes hydrolysis by the alkali it is advantageous there fore to recrystallise the benzoyl compounds whenever possible from ethanol or methylated spirit, since these solvents will esterify the unchanged chloride and so remove the latter from the recrystallised material. 

The Schotten-Baumann reaction may also be carried out, using, for example, benzene sulphonyl chloride, CeH,SO,Cl (. e., the acid chloride of benzene sulphonic acid, C H5SOjOH) in place of benzoyl chloride, and similar deri a-tives are obtained. Thus when phenol is dissolved in an excess of 10% sodium hydroxide solution, and then shaken with a small excess of benzene sulphonyl... 

The acidic properties of sulphonamides and their mono-substitution derivatives are particularly well illustrated in the alkyl ubstitution compounds, which by reason of these properties can be prepared by two distinct methods. Thus mono- and di-ethylamine, when subjected to the Schotten-Baumann reaction using benzenesulphonyl chloride, gi e benzenesulphonethylamide, and bcnzenesulphondiethylamide respectively. These compounds can also... 

Although benzenesulphonyl chloride has for simplicity been used in the above discussion, tolucne-/>- sulphonyl chloride, CHaCeH SO Cl, is more frequently used in the laboratory, owing to its much lower cost, the latter being due in turn to the fact that toluene-p-sulphonyl chloride is a by-product in the commercial preparation of saccharin. Toluene-p sulphonyl chloride is a crystalline substance, of m.p. 68° the finely powdered chloride will, however, usually react readily with amines in the Schotten-Baumann reaction it does not react so readily with alcohols, but the reaction may be promoted considerably by first dissolving the chloride in some inert water-soluble solvent such as acetone. 

Give benzoyl and toluene-/>-sulphonyl derivatives (Schotten-Baumann reaction) (p. 243) also benzene-sulphonyl derivatives. 

B) Benzoyl derivatives. Most amino-acids can be benzoyl-ated when their solutions in 10% aqueous sodium hydroxide are shaken with a small excess of benzoyl chloride until a clear solution is obtained (Schotten-Baumann reaction, p. 243). Acidification of the solution then precipitates the benzoyl derivative and the excess of benzoic acid, and the mixture must be filtered off, washed with water, and recrystallised (usually from ethanol) to obtain the pure derivative. (M.ps., p. 555 )... 

Benzoyl derivatives. Both primary and secondary amines form benzoyl derivatives under the conditions of the Schotten-Baumann reaction (see Section IV,52 and preceding discussion). 

By the Schotten-Baumann reaction. Under the usual Schotten-Baumann conditions (compare discussion preceding Section IV,52, also Section IV,100,2and Section IV,114,2), esters are readily formed, forexample ... 

Bemoyl chloride may replace acetyl chloride as a class reagent it possesses the advantage that it is only very slowly decomposed by cold water and consequently may be employed for detecting alcohols even in aqueous solution. The reaction is usually carried out in aqueous solution containing sufficient caustic alkali to decompose any excess of benzoyl chloride into the water-soluble alkali benzoate (Schotten - Baumann reaction compare Section IV,52). The benzoyl esters formed are insoluble in water ... 

Pinacol-pinacolone rearrangement Prileschajew epoxidation reaction Reformataky reaction Reimer-Tiemanii reaction Rosenmund reduction Sandmeyer reaction Schiemaim reaction Schmidt reaction or rearrangement Schotten-Baumann reaction Skraup reaction Sommelet reaction. ... 

Esterification of acid chlorides (Schotten-Baumann reaction) ... 

Schotten-Baumann reaction, 5, 745 stability, 5, 744 structure, 5, 736-743 substituents reactions, 5, 83... 

As with poly(vinyl alcohol), poly(vinyl cinnamate) is prepared by chemical modification of another polymer rather than from monomer . One process is to treat poly(vinyl alcohol) with cinnamoyl chloride and pyridine but this is rather slow. Use of the Schotten Baumann reaction will, however, allow esterification to proceed at a reasonable rate. In one example poly(vinyl alcohol) of degree of polymerisation 1400 and degree of saponification of 95% was dissolved in water. To this was added a concentrated potassium hydroxide solution and then cinnamoyl chloride in methyl ethyl ketone. The product was, in effect a vinyl alcohol-vinyl cinnamate copolymer Figure 14.8)... 

Tosylates are generally formed from an amine and tosyl chloride in an inert solvent such as CH2CI2 with an acid scavenger such as pyridine or triethyl-amine, They may also be prepared using the Schotten-Baumann reaction. 

Also via the route of the acid chloride followed by reaction with taurine or methyltaurine solution in water under the Schotten-Baumann reaction are created the taurides and methyltaurides of the ether carboxylic acids [44] ... 

The acid chloride route of the Schotten-Baumann reaction can be carried out continuously [6] while completeness of the reaction can be assured by rapid recirculation of the reaction product [7]. These compounds are used in specialty applications, such as shampoos or soap-syndet toilet bars [8]. 

As one would anticipate, the time honored Schotten-Baumann reaction and its variants are the key steps in putting this group of substances together. Their intrinsic interest to the medicinal chemist depends upon their pharmacological properties and, in some cases, preparation of some of the less common benzoic acid analogues. 

Schotten-Baumann reaction to give clopamide. The related diuretics diapamide (36),14 xipamide (37),15... 

In 3, the amino functional group is two methylene units removed from the ferrocene nucleus. It appears from the instantaneous and quantitative formation of h from 3 that this feature minimizes steric effects and also enables 3 to undergo the Schotten-Baumann reaction readily without the classical a-metallocenylcarbenium ion effects providing any constraints. The IR spectrum of showed the characteristic N-H stretch at 3320 cm" (s), the amide 1 (carbonyl) stretch at 1625 an - -(s), the amide II (N—H) stretch at 1540 cm (s), and the amide III band at 1310 cm 1(m). In addition, characteristic absorptions of the ferrocenyl group were evident at 1100 and 1000 cm l (indicating an unsubstituted cyclopentadienyl ring) and at 800 cm"l. 

Scholl reaction, 12 171 Schotten-Baumann procedure, 10 485 Schotten-Baumann reaction, 19 798 Schottky barrier, 19 137, 138 Schottky barrier arrays, platinum silicide, 19 157-158... 

In other reactions also the OH-group of the phenols shows itself to be more reactive than that of the aliphatic alcohols. Phenols, but not alcohols, react easily with diazomethane. With other alkylating agents also, such as alkyl halides, and dialkyl sulphates, the phenols react even in aqueous alkaline solution whilst the alcohols do not react under such conditions. Benzoyl derivatives, most of which crystallise readily, are excellently adapted for the characterisation of phenols (Schotten-Baumann reaction). 

---