Radikalische Cyclisierung von Dienen, VIII. Über die regioselektive Herstellung von ungesättigten Cyclopenta[b]furan‐2‐onen aus (S)‐(+)‐Carvon — Bausteine zur Synthese von enantiomerenreinen Triquinanen

Radical‐Type Cyclization of Dienes, VIII[1]. — On the Regioselective Synthesis of Unsaturated Cyclopenta[b]furan‐2‐ones from (S)‐(+)‐Carvone — Building Blocks for the Synthesis of Enantiomerically Pure Triquinanes The diastereomeric products 2a and 2b, which were synthesized from (S)‐(+)‐carvone (1), are converted to (3aS,5S,6aS)‐(‐)‐5‐acetoxyhexahydro‐6a‐methyl‐2H‐cyclopenta[b]furan‐2‐one (4) in ca. 50% yield. 4 is regioselectively converted to (3aR,6aS)‐(‐)‐3,3a,6,6a‐tetrahydro‐6a‐methyl‐ (8a) and (3aS,6aR)‐(+)‐3,3a,4,6a‐tetrahydro‐6a‐methyl‐2H‐cyclopenta[b]‐furan‐2‐one (8b). These are used at the 10‐g scale for the synthesis of enantiomerically pure triquinanes.