Stereocontrolled Cascade Cyclisation of Campholenic Enol Ether Derivatives: En Route to Vetiver-Scented Spiroxides

Spirocyclic Compounds in Fragrance Chemistry: Synthesis and Olfactory Properties

In this Review, both the scientific literature and patents have been analysed to gather, examine and classify synthetic strategies developed to access spirocyclic molecules having olfactory properties of interest for the perfume industry. New structures have been reported at a steady state since 1961 with a particularly intense activity in the 80's. In the diversity of olfactory properties observed, spirocyclic molecules were found to be quite frequently woody, as well as fruity and ambery, among other tonalities. More recent data reflect the evolution of modern synthetic organic chemistry towards bioinspiration, enantioselective reactions, green and sustainable chemistry and biotechnology.

Synthesis of Cyclic Fragrances via Transformations of Alkenes, Alkynes and Enynes: Strategies and Recent Progress

With increasing demand for customized commodities and the greater insight and understanding of olfaction, the synthesis of fragrances with diverse structures and odor characters has become a core task. Recent progress in organic synthesis and catalysis enables the rapid construction of carbocycles and heterocycles from readily available unsaturated molecular building blocks, with increased selectivity, atom economy, sustainability and product diversity. In this review, synthetic methods for creating cyclic fragrances, including both natural and synthetic ones, will be discussed, with a focus on the key transformations of alkenes, alkynes, dienes and enynes. Several strategies will be discussed, including cycloaddition, catalytic cyclization, ring-closing metathesis, intramolecular addition, and rearrangement reactions. Representative examples and the featured olfactory investigations will be highlighted, along with some perspectives on future developments in this area.