Geranic acid derivatives

Frankhauser etal, US Patent 6,384,242 (May 7, 2002) Assignee Firmenich SA and Lonza AG Utility Fragrance and Perfume Component 

A vessel was charged with 6-methyl-5-hepten-2-one (1.0 mol) and 516g CH2CI2, cooled to — 19°C, and boron trifluoride etherate (0.5 mol) and ketene gas metered in over the course of 4 hours. Throughout this period the temperature was maintained between — 12°C and — 14°C. Thereafter urotropine (2.5 mmol) was added and the solution stirred for 30 minutes at 0°C. The solvent was evaporated at 15 mbarr at 20 °C and the product isolated in 80.9% yield by vacuum distillation. H-NMR and mass spectrum data supplied. 

(+/—)-3-Hydroxy-3,7-dimethyl-oct-6-enoic acid [3-hydroxycitronellic acid] 

The product from Step 1 (0.259 mol) was dissolved in 180 ml 2M NaOH containing tributylbenzylammonium chloride (0.49 g) whereupon the temperature rose to 51 °C and stirred for 2.5 hours. The mixture was cooled to 20 °C and stirred overnight. The product was extracted twice with 100 ml diethyl ether, acidified with 390 ml 1M HCl, dried, and the product isolated in 83.4% yield as a yellow oil. 

The oligomeric ester, (I), of the product of Step 1 was also by the author and is described  

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