All-Catalytic, Efficient, and Asymmetric Synthesis of α,ω-Diheterofunctional Reduced Polypropionates via “One-Pot” Zr-Catalyzed Asymmetric Carboalumination−Pd-Catalyzed Cross-Coupling Tandem Process

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Abstract
A highly efficient method for the synthesis of stereochemically pure (≥99% ee and >50/1 dr) α,ω-diheterofunctional reduced polypropionates has been developed. The essential features of the method are represented by the conversion of inexpensive styrene into 2-methyl-4-phenyl-1-pentanol (1) in 50% yield over two steps from styrene via Zr-catalyzed asymmetric carboalumination (ZACA) reaction in the presence of (NMI)2ZrCl2 and Pd-catalyzed vinylation of the in situ generated isoalkylalanes in the presence of Zn(OTf)2 and a catalytic amount of Pd(DPEphos)Cl2. This ZACA−Pd-catalyzed vinylation may be repeated as needed without purification. After the final ZACA reaction, oxidation with O2 provides α-hydroxy-ω-phenyl reduced polypropionates, which can be fully or partially purified by chromatography. After acetylation, Ru-catalyzed oxidative cleavage of the Ph ring, and reduction with BH3·THF, the second chromatographic purification provides stereoisomerically pure α,ω-diheterofunctional reduced polypropionates (e.g., 9 and 11) that can be further converted to key intermediates 6 and 7 for the synthesis of ionomycin (4) and borrelidin (5), respectively, by known reactions.

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