Improvements in or relating to methods for synthesizing vitamin a-active material and intermediates thereof

摘要

The invention comprises 1,1-dialkoxy-3,7-dimethyl - 3,7 - dihydroxy - 9 - (2,6,6 - trimethyl cyclohex - 1 - enyl) - nona - 8 - ene - 4 - yne and the preparation thereof by reacting b -ionone with a propinyl halide, e.g. propargyl bromide in the presence of a metal, such as zinc or magnesium, thereby forming the carbinol 4-methyl-4 - hydroxy - 6 - (2,6,6 - trimethyl cyclohex - 1-enyl) - hex - 5 - ene - 1 - yne, and reacting said ethinyl carbinol with an acetal of b -ketobutyraldehyde. Subsequently the acetylenic 3,7 - diol acetal may be hydrogenated to a 1,1 - dialkoxy - 3,7 - dimethyl - 3,7 - dihydroxy-9 - (2,6,6 - trimethyl cyclohex - 1 - enyl) - nona-4,8 - diene. The olefinic 3,7 - diol acetal is converted to Vitamin A aldehyde by subjecting successively to dehydration, hydrolysis by means of an ionizable acid and treatment with a basic catalyst or alternatively the conversion may be effected in a single step with a mixture of an organic base and an ionizable acid. Vitamin A alcohol is obtained by subjecting the olefinic 3,7-diol acetal successively to dehydration, hydrolysis by means of an ionizable acid and treatment with a basic reducing agent. The ethinyl carbinol is condensed with an acetal of b -ketobutyraldehyde by means of a Grignard reaction. Examples describe the production of Vitamin A alcohol and aldehyde starting with b -ionone.