DIRECT ACCESS TO SUBSTITUTED BRENDANE DERIVATIVES BY PALLADIUM-COPPER MEDIATED CYCLIZATION OF ENDO-5-VINYL-2-NORBORNENE - X-RAY STRUCTURE OF THE SIGMA-PI INTERMEDIATE PALLADIUM COMPLEX - FURTHER EVOLUTION (BAEYER-VILLIGER OXIDATION) TO THE QUINANE SYSTEM

A one-step synthesis of disubstituted brendane derivatives is described starting from (commercially) available vinyl norbornene by the Wacker-type oxidation with PdCl2/CuCl2 or PdCl2/CuCln/O-2 (n=1,2). In addition to the formation of a new carbon-carbon bond two different nucleophilic groups are incorporated with complete chemio-, regio- and high (>90%) stereoselectivity. The NMR and X-Ray structure analysis of a sigma-pi-palladium-bipyridine complex clearly establishes the stereochemistry of the prerogative intermediate and the position of the coordinated vinyl group in an 'extracyclic' position before the insertion-cyclisation step. This stereochemistry establishes the oxidative cleavage of the cyclised (cis-insertion) organopalladium intermediate to proceed with predominant (90%) inversion of configuration. A further ring opening reaction via Baeyer-Villiger oxidation has been developed showing the usefullness of the brendane derivatives far an easy access to functionalized quinane system(s) with complete stereocontrol of 5 stereogenic centers.