Catalytic Stereoselective Formation of C–O, C–C and C–B Bonds A Voyage from Asymmetric Reactions Enabled by Lipases to Stereoselective Palladium-Catalyzed Oxidative Transformations of Enallenes

Abstract: This thesis has been focused on enzymatic kinetic resolutions and stereoselective oxidative transformations of enallenes catalyzed by PdII.In the first part of the thesis, a detailed discussion on Candida antarctica lipase B (CALB)-catalyzed kinetic resolution (KR) of δ-functionalized alkan-2-acetates is shown. We gained a deeper insight into the mechanism of enzyme-substrate recognition. Changing from an anhydrous solvent to water or a water-containing organic solvent enhanced the enantioselectivity. The effect of –OH was also confirmed by a lipase mutant suggesting that the water molecule mentioned above can be partly mimicked.In the second part of the thesis, we developed an efficient KR for allenic alcohols. On this basis, a novel synthesis of optically pure 2-substituted 2,3-dihydrofurans from allenic alcohols via a Ru-catalyzed cycloisomerization was reported. The developed protocol enabled us to assemble an optically pure precursor for total synthesis with three chiral centers from readily available allenol in 2 days.In the third part, we reported a class of reactions involving C–H cleavage under mild conditions: PdII-catalyzed oxidative transformations of enallenes. These reactions are particularly attractive since a number of meticulous structures have been achieved from readily accessible starting materials. The directing effect of an unsaturated hydrocarbon was found to be key for these transformations.In the final part, we developed the carbonylative insertion reaction discussed in the third part of the thesis into an asymmetric version. By using this methodology, a number of cyclopentenone compounds were obtained in good to excellent enantioselectivity.