A Practical Domino‐ Claisen–Cope Sequence in the Synthesis of New Blooming Citrus and Potent Floral Rose Alcohols

Fifty years after its first discovery by Alan Francis Thomas , we describe a versatile, metal and pressure‐free domino‐ Claisen–Cope rearrangement using the readily available α , β ‐unsaturated aldehydes 5 or their acetals 5′ and allylic alcohols 6 . This transformation provides a convenient access to a large number of radiant citrus and floral rosy odorants. Odor profiles of novel floral rosy and citrus alcohols 13 , 14 , and 16 were studied. Compound 14ba has a floral, rosy, geranium‐like character and shows unique performance and diffusiveness. Compound 16ba has a clear main citrus odor character with a clean green grapefruit/rhubarb connotation. Both odorants have been successfully introduced to perfumery recently as Rosyfolia ™ ( 14ba ) and Pomelol ™ ( 16ba ).