Novel process for the manufacture of methyl limonitrile

A process for the manufacture of methyl limonitrile of olfactive quality comprising a mixture of 3,7-dimethyl-2,6-nonadiene nitrile, 3,7-dimethyl-3,6-nonadiene nitrile and 7-methyl-3-methylene-6-nonene nitrile comprising the following steps:

• a) reacting 6-methyl-5-octen-2-one with cyano acetic acid and removing carbon dioxide and water, wherein the reaction and the removal of carbon dioxide and water are performed in the presence of pyridine as base and 1,4-diamino butane as co-base in toluene as organic solvent;
• b) removing toluene and pyridine by distillation to obtain a reaction mixture;
• c) isomerizing the reaction mixture obtained after having performed step b) to obtain an isomerized reaction mixture;
• d) extracting the isomerized reaction mixture with diluted acids whereby an organic phase and an aqueous phase are formed, separating the organic phase containing the methyl limonitrile from the aqueous phase, and washing the organic phase one or more times with deionized water;
• d-2) optionally back-extracting the aqueous phase obtained in step d) with toluene and afterwards removing the toluene, whereby the thus removed toluene is optionally recycled into step d-2);
• e) separating off coloured components and high boiling impurities from the organic phase obtained in step d);
• f) separating off low boiling impurities from the distillate obtained in step e), whereby these low boiling impurities contain unconverted 6-methyl-5-octen-2-one;
• f2) optionally recycling the 6-methyl-5-octen-2-one back into step a).