Preparation of polyunsaturated ketones

US4431844A · kind A · utility

Assignee

• BASF SE

Inventors

• Lothar Janitschke · Kleinniedesheim, DE
• Werner Hoffmann · Ludwigshafen, DE
• Lothar Arnold · Heidelberg, DE
• Manfred Stroezel · Ilvesheim, DE
• Hans-Juergen Scheiper · Mutterstadt, DE

Key dates

• Filing date: Mar 24, 1982
• Grant date: Feb 14, 1984
• Expiry date: Mar 24, 2002

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C07C45/74
• WIPO field: Organic fine chemistry
• WIPO sector: Chemistry

Abstract

An improved process for the preparation of unsaturated ketones of the general formula I ##STR1## where R.sup.1 is --CH.sub.3, ##STR2## and R.sup.2 and R.sup.3 are different and each is H or --CH.sub.3, by reacting an aldehyde of the general formula II ##STR3## with a molar excess of acetone or methyl ethyl ketone at an elevated temperature in the presence of an aqueous alkali metal hydroxide solution, wherein (a) all the reactants are mixed thoroughly, (b) the temperature is kept at from 10 to 120.degree. C. above the boiling point of the lowest-boiling component and (c) the pressure is kept at from p to 100 bar, where p is the vapor pressure of the mixture at the reaction temperature. The products methylpseudoionone, dimethylpseudoionone, pseudoirone, methylpseudoirone and dimethylpseudoirone are useful scents and scent intermediates. In addition, pseudoionone is an important intermediate for the industrial preparation of vitamin A, and 6-methyl-hepta-3,5-dien-2-one is a sought-after aromatic.