(±)-1-[(1R,2R,8aS)-1,2,3,5,6,7,8,8a-Octahydro-1,2,8,8-tetramethylnaphthalen-2-yl]ethan-1-one: Isolation and Stereoselective Synthesis of a Powerful Minor Constituent of the Perfumery Synthetic Iso E Super

• Published in: Helvetica chimica acta Vol. 82; no. 7; pp. 1016 - 1024
• Main Authors: Nussbaumer, Cornelius, Fráter, Georg, Kraft, Philip
• Format: Journal Article
• Language: English
• Published: Basel Verlag Helvetica Chimica Acta 07.07.1999; Wiley
• Subjects: Chemistry; Chemistry, Multidisciplinary; Physical Sciences; Science & Technology
• ISSN: 0018-019X; 1522-2675
• DOI: 10.1002/(SICI)1522-2675(19990707)82:7<1016::AID-HLCA1016>3.0.CO;2-Y

(±)‐1‐[(1R*,2R*,8aS*)‐1,2,3,5,6,7,8,8a‐Octahydro‐1,2,8,8‐tetramethylnaphthalen‐2‐yl]ethan‐1‐one (5) was identified as a minor (ca. 5%) but very powerful (5 pg/l (air)) constituent of the important perfumery synthetic Iso E Super®. Its structure was assigned by NMR spectroscopy and established by a stereoselective synthesis starting from α‐ionone (10). Diastereoselective conjugate addition of Me2CuLi to 10 was followed by a haloform reaction, esterification, and isomerization of the C=C bond by treatment with NaOCl (Schemes 3 and 4). The resulting allyl chloride 17 was ozonized and transformed into the trimethyl(vinyl)octahydrocoumarin 20 by diastereoselective Grignard reaction with ethynylmagnesium chloride, and subsequent Lindlar hydrogenation. Ireland‐Claisen rearrangement of 20 followed by methylation with MeLi afforded the target molecule 5 that was identical with the material isolated from commercial Iso E Super®.