DIRECT ACCESS TO SUBSTITUTED BRENDANE DERIVATIVES BY PALLADIUM-COPPERMEDIATED 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 describe d starting from (commercially) available vinyl norbornene by the Wacke r-type oxidation with PdCl2/CuCl2 or PdCl2/CuCln/O-2 (n=1,2). In addit ion to the formation of a new carbon-carbon bond two different nucleop hilic groups are incorporated with complete chemio-, regio- and high ( >90%) stereoselectivity. The NMR and X-Ray structure analysis of a sig ma-pi-palladium-bipyridine complex clearly establishes the stereochemi stry of the prerogative intermediate and the position of the coordinat ed vinyl group in an 'extracyclic' position before the insertion-cycli sation step. This stereochemistry establishes the oxidative cleavage o f the cyclised (cis-insertion) organopalladium intermediate to proceed with predominant (90%) inversion of configuration. A further ring ope ning reaction via Baeyer-Villiger oxidation has been developed showing the usefullness of the brendane derivatives far an easy access to fun ctionalized quinane system(s) with complete stereocontrol of 5 stereog enic centers.