| 摘要 |
The invention comprises 1,1-dialkoxy-3-methyl - 3 - hydroxy - hex - 5 - yne and the preparation thereof by reacting an acetal of acetoacetaldehyde with propargyl halide in the presence of a metal, e.g. zinc or magnesium. Subsequently the carbinol may be condensed with b -ionone to form an acetylenic 3,7-diol acetal which may be partially hydrogenated to the corresponding olefinic 3,7-diol acetal. Vitamin A aldehyde 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 catalyst or alternatively the conversion may be effected in one step by treatment with a mixture of an ionizable acid and a basic catalyst. Vitamin A alcohol is obtained by subjecting the olefinic 3,7-diol to dehydration, hydrolysis by means of an ionizable acid, and treatment with a basic reducing agent. The ethinyl carbinol is condensed with b -ionone by means of a Grignard reaction. The dehydration of the 3,7-diol acetal may be effected by means of a phosphorus halide or oxyhalide, preferably in the presence of an amine. Examples describe the production of Vitamin A alcohol and aldehyde starting with b -ionone.
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