Wenker process

The Wenker process (364), carried out by BASF and various other companies since the end of the 1960s, is a distinct improvement. In this process the hemisulfate of monoethanol amine, a nonvolatile, crystalline substance, is used in place of volatile 2-chloroethylamine for the alkaline cyclisation. The reaction can be carried out under pressure (365). 

The mechanism for the Wenker aziridine synthesis is very straightforward. As depicted by conversion 2—>3, the transformation is a simple case of intramolecular Sn2 displacement process, in which the sulfate ester is the leaving group. 

This class of aziridine-forming reaction includes the first reaction reported to afford aziridines. In 1888 Gabriel reported that aziridines could be prepared in a two-step process, by chlorination of ethanolamines with thionyl chloride, followed by alkali-induced cyclization [75]. Wenker subsequently reported that heating of 600 g of ethanolamine with more than 1 kg of 96 % sulfuric acid at high temperature produced P-aminoethyl sulphuric acid 282 g of it was distilled from aqueous base to give 23 g of aziridine itself, the first preparation of the parent compound in a pure condition [76]. Though there is no evidence to substantiate the hypothesis, the intermediate in these reactions is perhaps a cyclic sulfamidate (Scheme 4.51). 

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