Preparation of optically active flowery and woody‐like odorant ketones <i>via Corey</i>‐<i>Chaykovsky</i> oxiranylation: Irones and analogues

Abstract

Abstract α‐, β‐, and γ‐Irones and analogues have been prepared from optically active ketones (+)‐ 1 , (+)‐ 6a,b , and (+)‐ 17 , via a Corey‐Chaykovsky oxiranylation (Me 2 S, Me 2 SO 4 , Me 2 SO, NaOH) followed by isomerisation (SnCl 4 or MgBr 2 ). (+)‐Dihydrocyclocitral ( 19a ), obtained from (−)‐citronellal, and analogue (+)‐ 19b , were condensed with various ketones to afford (+)‐ 21a–f , and after hydrogenation (+)‐ 22a–f. A mild oxidative degradation of aldehydes (+)‐ trans ‐and (−)‐ cis ‐ 8a,b , to ketones (−)‐ 16a,b , as well as olfactive evaluations, 13 C‐NMR assignments, and absolute configurations of the intermediate epoxides, aldehydes, and alcohols are presented.