Palladium‐Catalysed Intramolecular Cyclisations of Olefinic Propargylic Carbonates and application to the diastereoselective synthesis of enantiomerically pure (−)‐α‐thujone

Abstract

Abstract Intramolecular [Pd 2 (dba) 3 ]/tri(2‐furyl)phosphine‐catalysed (dba = dibenzylideneacetone, PhCHCHCOCHCHPh) cyclisations of olefinic propargylic carbonates I provided alk‐1‐enyl‐(3‐aza)bicyclo[3.1.0]‐hexanes VIII in good yields. A palladium cascade sequence I → II → III → IV → VII → VIII is proposed. Furthermore, chiral propargylic carbonates such as 23 , 24 and 25 allowed diastereoselective formation of bicyclo[3.1.0]hexanes 29 , 30 and 31 , respectively. The first diastereoselective synthesis of the monoterpene, (−)‐α‐thujone 40 illustrates the potential of the method.