Enantioselective Synthesis of (−)‐β‐Santalol by a Copper‐Catalyzed Enynol Cyclization–Fragmentation Reaction

The right cat for the desired odor: The key step in an enantioselective synthesis of the prized fragrance (−)-β-santalol was a highly selective copper-catalyzed cyclization–fragmentation reaction of an enynol (see scheme). When a platinum catalyst was used for the cyclization step, the desired fragmentation did not take place; instead, a product containing a cyclopropane ring was formed with 100 % selectivity.