Reactions using lewis acids

摘要

In a method of performing a chemical reaction using a Lewis acid, after reaction the Lewis acid is extracted from the reaction product in the form of an aqueous solution, followed by drying of the aqueous solution of the Lewis acid. The dried Lewis acid can be reused in a further similar reaction. The method can be repeated several times, using the same batch of Lewis acid, without the activity and specificity of the Lewis acid being significantly affected. The invention has been used to good effect in the preparation of isopulegol from citronellal using zinc bromide as a Lewis acid catalyst for the cyclisation reaction. The invention can thus provide an environmentally acceptable and efficient process for the production of isopulegol from citronellal, in both racemic and enantiomerically pure forms.