Total synthesis 2-epi-α-cedren-3-one via a cobalt-catalysed Pauson-Khand reaction. Issue 38 (20th September 2018) - Kerr, William J.
Abstract: Herein we target the total synthesis of 2- epi -α-cedren-3-one, a natural compound isolated from the essential oil of Juniperus thurifera . Overall, our synthetic sequence presents an optimised and robust series of chemical transformations, with prominent features including a low temperature and highly ( Z )-selective Wittig olefination reaction, which is vital for the establishment of the relative stereochemistry within the final natural product, and a microwave-assisted, catalytic, intramolecular Pauson-Khand cyclisation reaction, which is used to construct the intriguing tricyclic core of the target molecule. Our optimum cyclisation protocol utilises only 20 mol% of transition metal, and delivers the complex tricyclic structure in just 10 min. Further manipulations of the annulation product culminate in the first total synthesis of the described natural target. Graphical abstract: Image 1