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Subject: transformation × WGL Institute: LIKAT ×

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    Homogeneous and heterogeneous catalytic reduction of amides and related compounds using molecular hydrogen
    ([London] : Nature Publishing Group UK, 2020) Cabrero-Antonino, Jose R.; Adam, Rosa; Papa, Veronica; Beller, Matthias
    Catalytic hydrogenation of amides is of great interest for chemists working in organic synthesis, as the resulting amines are widely featured in natural products, drugs, agrochemicals, dyes, etc. Compared to traditional reduction of amides using (over)stoichiometric reductants, the direct hydrogenation of amides using molecular hydrogen represents a greener approach. Furthermore, amide hydrogenation is a highly versatile transformation, since not only higher amines (obtained by C–O cleavage), but also lower amines and alcohols, or amino alcohols (obtained by C–N cleavage) can be selectively accessed by fine tuning of reaction conditions. This review describes the most recent advances in the area of amide hydrogenation using H2 exclusively and molecularly defined homogeneous as well as nano-structured heterogeneous catalysts, with a special focus on catalyst development and synthetic applications.
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    The role of allyl ammonium salts in palladium-catalyzed cascade reactions towards the synthesis of spiro-fused heterocycles
    ([London] : Nature Publishing Group UK, 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.
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    Direct synthesis of benzylic amines by palladium-catalyzed carbonylative aminohomologation of aryl halides
    ([London] : Macmillan Publishers Limited, part of Springer Nature, 2018) Peng, Jin-Bao; Wu, Fu-Peng; Xu, Cong; Qi, Xinxin; Ying, Jun; Wu, Xiao-Feng
    Benzylic amines are valuable compounds with important applications in areas including pharmaceuticals and agrochemicals. The known procedures for their synthesis are limited by difficulties in functionalizing the parent aminomethyl groups. On the other hand, carbonylation reactions offer a potent method to introduce carbonyl groups and homologate carbon chains. However, carbonylative aminohomologation of aryl halides is challenging due to competing reactions and the need to balance multiple sequential steps. Here we report a palladium-catalyzed carbonylative aminohomologation reaction for the direct aminomethylation of aryl halides. The reaction proceeds via a tandem palladium-catalyzed formylation, followed by imine formation and formic acid-mediated reduction. Useful functional groups including chloride, bromide, ester, ketone, nitro, and cyano are compatible with this reaction. Both aryl iodides and bromides are suitable substrates and a wide range of synthetically useful amines are efficiently obtained in moderate to excellent yields.