Schotten-Baumann procedure

The acid chlorides are generally more reactive than the corresponding acid anhydrides. In fact, the alcoholysis of acid chlorides is probably the best laboratory method for preparing esters. Frequentiy, basic materials are added during the course of the reaction to neutralize by-product hydrochloric acid. When the basic material is aqueous caustic, the procedure is referred to as the Schotten-Baumann procedure (73). Esterification of tertiary alcohols by acid chlorides is described in Reference 74. Esters of tertiary alcohols can also be formed through an intermediate /-butyl thioate group (75) ... 

The choice of which reactions to include is not an easy one. First there are the well known "Name Reactions", that have appeared in various monographs or in the old Merck index. Some of these are so obvious mechanistically to the modern organic chemistry practitioner that we have in fact omitted them for instance esterification of alcohols with acid chlorides - the Schotten-Baumann procedure. Others are so important and so well entrenched by name, like the Baeyer-Villiger ketone oxidation, that it is impossible to ignore them. In general we have kept older name reactions that are not obvious at first glance. 

The reaction between acyl halides and alcohols or phenols is the best general method for the preparation of carboxylic esters. It is believed to proceed by a 8 2 mechanism. As with 10-8, the mechanism can be S l or tetrahedral. Pyridine catalyzes the reaction by the nucleophilic catalysis route (see 10-9). The reaction is of wide scope, and many functional groups do not interfere. A base is frequently added to combine with the HX formed. When aqueous alkali is used, this is called the Schotten-Baumann procedure, but pyridine is also frequently used. Both R and R may be primary, secondary, or tertiary alkyl or aryl. Enolic esters can also be prepared by this method, though C-acylation competes in these cases. In difficult cases, especially with hindered acids or tertiary R, the alkoxide can be used instead of the alcohol. Activated alumina has also been used as a catalyst, for tertiary R. Thallium salts of phenols give very high yields of phenolic esters. Phase-transfer catalysis has been used for hindered phenols. Zinc has been used to couple... 

Because the reaction of an amine with an acyl chloride is much faster than the hydrolysis of the acyl chloride, the reaction can usually be carried out in an aqueous alkali solution. This is well known as the Schotten-Baumann procedure.6 For example, a number of N-acyl taxol analogs have been prepared under Schotten-Baumann conditions by the reaction of A-debenzoyltaxol with various acid chlorides (Eq. 9.4).7 Highly purified /V-long-chain-acyl neutral amino acids such as potassium AMauroyTy-aminobutyrate, useful as surfactants for detergent... 

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... 

Another interesting example of resolution through formation of diastereo-mers is the isolation of four stereoisomers of 3-amino-2-methyl-3-trifluoro-methyl butanoic acid [55]. In this process, the chemical-enzymatic method by the combination of chemical and enzymatic reaction is a very convenient. At first, -phenylacetyl derivatives 61a and 61b were prepared in excellent isolated yields via the Schotten-Baumann procedure. After these materials were hydrolysed with penicillin acylase (EC 3.5.1.11) from Escherichia coli until attainment of 50% conversion, enzymatically unconverted -phenylacetyl derivatives 62 a and 62 b (organic layer) and amino acids 63 b and 63 d (aqueous layer) were separated. Acidic hydrolysis of unconverted materials produced other stereoisomers 63 a and 63 c in high optical pure form. 

Oxazolin-5-ones have also proven to be important intermediates in the homologation of carboxylic acids (71AG(E)655). The IV-acyl-DL-valine derivative (402), prepared from the acid chloride of the carboxylic acid and DL-valine by the Schotten-Baumann procedure, was treated with excess acetic anhydride to afford (403). Reaction of (403) with acrylonitrile and triethylamine led to (404) in good yield. Hydrolysis of (404) with dilute alkali or acid gave the y-keto nitrile or y-keto acid (Scheme 89). 

POLYMERSCONTAINING SULFUR - POLYSULFONES] (Vol 19) Schotten-Baumann procedure... 

The benzanilide should be of good quality, or tarry material will form and interfere with purification of the product. Benzanilide is readily made by the Schotten-Baumann procedure from aniline, 10% aqueous sodium hydroxide, and benzoyl chloride in the proportions 6 30 5, and after crystallization from 95% ethanol is sufficiently pure. 

Acylations of pyridazinones, maleic hydrazide, and related compounds are known. Either 0-acylation or A-acylation is reported. Using the Schotten-Baumann procedure maleic hydrazide is O-acylated with benzoyl chloride and chlorocarbonates and similarly 0-sulphonyl and phosphoryl derivatives have been prepared. ... 

This report also describes reactions with acid chlorides (the Schotten-Baumann procedure), nitrourea, o-methylisouronium salts, and (S-alkyliso-thiouronium salts. A more impressive example of the same general type is the following ... 

Helferich found that phenols can be mesylated, either in pyridine or by the Schotten-Baumann procedure, and found that the mesylates are extraordinarily... 

In a procedure for Ihc preparation of their diazomethane precursor, p-tolyl-siiifunyimethylnitrosamidc. de Boer and Backer carried out the reaction of tosyi chloride with methylaminc by the Schotten-Baumann procedure, that is with the alternating adiitlen of acid chloride and sodium hydroxide solution. 

Esters of thiocarboxylic acids are formed on acylation of thiols by acid anhydrides. For the preparation of the lower 5-esters the following Schotten-Baumann procedure is used 430,431... 

Aryl arenesulfonates mostly crystallize readily and are useful for identification of phenols or sulfonic acids they are easily obtained from the acid chlorides and phenols in the presence of alkali689 or a tertiary base690 by the Schotten-Baumann procedure. 

Sulfinyl chlorides, analogously to sulfonyl chlorides, are important starting materials for the preparation of other sulfinic acid derivatives. Thus, when warmed with alcohols they give sulfinic esters,712 713 and esterification can also be carried out by the Schotten-Baumann procedure in the presence of pyridine or potassium carbonate.714... 

---