Vitamin A is a lipid-soluble vitamin, which is essential for the vision process, growth, and cell functions. Dietary deficiency symptoms are e.g. reduced immune response and growth retardation in animals and night blindness in humans. On an industrial scale vitamin A is produced by chemical synthesis based on β-ionone. In 100 years of vitamin research only three vitamin A processes have been industrialized. All production processes apply stoichiometric reactions with activated reagents : which generate equimolar amounts of by-products. A direct catalytic route to vitamin A acetate (avoiding protecting group chemistry) does not exist so far.
Several catalytic coupling reactions were investigated using compounds based on β-ionone as preferred starting material for the cyclohexene moiety of vitamin A acetate, in combination with a variety of other smaller (< C6) building blocks. With these methods, the use of stoichiometric coupling conditions resulting in the formation of equimolar amounts of waste streams can be avoided.