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Ligand-Controlled Palladium-Catalyzed Carbonylation of Alkynols : Highly Selective Synthesis of α-Methylene-β-Lactones
2020, Ge, Yao, Ye, Fei, Liu, Jiawang, Yang, Ji, Spannenberg, Anke, Jiao, Haijun, Jackstell, Ralf, Beller, Matthias
The first general and regioselective Pd-catalyzed cyclocarbonylation to give α-methylene-β-lactones is reported. Key to the success for this process is the use of a specific sterically demanding phosphine ligand based on N-arylated imidazole (L11) in the presence of Pd(MeCN)2Cl2 as pre-catalyst. A variety of easily available alkynols provide under additive-free conditions the corresponding α-methylene-β-lactones in moderate to good yields with excellent regio- and diastereoselectivity. The applicability of this novel methodology is showcased by the direct carbonylation of biologically active molecules including natural products. © 2020 The Authors. Published by Wiley-VCH GmbH
The role of allyl ammonium salts in palladium-catalyzed cascade reactions towards the synthesis of spiro-fused heterocycles
2020, Ye, Fei, Ge, Yao, Spannenberg, Anke, Neumann, Helfried, Beller, Matthias
There is a continuous need for designing new and improved synthetic methods aiming at minimizing reaction steps while increasing molecular complexity. In this respect, catalytic, one-pot cascade methodologies constitute an ideal tool for the construction of complex molecules with high chemo-, regio-, and stereoselectivity. Herein, we describe two general and efficient cascade procedures for the synthesis of spiro-fused heterocylces. This transformation combines selective nucleophilic substitution (SN2′), palladium-catalyzed Heck and C–H activation reactions in a cascade manner. The use of allylic ammonium salts and specific Pd catalysts are key to the success of the transformations. The synthetic utility of these methodologies is showcased by the preparation of 48 spiro-fused dihydrobenzofuranes and indolines including a variety of fluorinated derivatives.