Rh-Catalyzed C[BOND]C Cleavage of Benzyl/Allylic Alcohols to Produce Benzyl/Allylic Amines or other Alcohols by Nucleophilic Addition of Intermediate Rhodacycles to Aldehydes and Imines

Authors

  • Xi-Sha Zhang,

    1. Beijing National Laboratory of Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry and PKU Green Chemistry Center, Peking University, Beijing 100871 (P.R. China), Fax: (+86) 10-6276-0890
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  • Dr. Yang Li,

    1. Beijing National Laboratory of Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry and PKU Green Chemistry Center, Peking University, Beijing 100871 (P.R. China), Fax: (+86) 10-6276-0890
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  • Hu Li,

    1. Beijing National Laboratory of Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry and PKU Green Chemistry Center, Peking University, Beijing 100871 (P.R. China), Fax: (+86) 10-6276-0890
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  • Kang Chen,

    1. Beijing National Laboratory of Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry and PKU Green Chemistry Center, Peking University, Beijing 100871 (P.R. China), Fax: (+86) 10-6276-0890
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  • Zhi-Quan Lei,

    1. Beijing National Laboratory of Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry and PKU Green Chemistry Center, Peking University, Beijing 100871 (P.R. China), Fax: (+86) 10-6276-0890
    2. Chengdu Institute of Biology, Chinese Academy of Sciences Chengdu, Sichuan 610068 (P.R. China)
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  • Prof. Dr. Zhang-Jie Shi

    Corresponding author
    1. Beijing National Laboratory of Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry and PKU Green Chemistry Center, Peking University, Beijing 100871 (P.R. China), Fax: (+86) 10-6276-0890
    2. State Key Laboratory of Organometallic Chemistry, Chinese Academy of Sciences, Shanghai 200032 (P.R. China)
    • Beijing National Laboratory of Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry and PKU Green Chemistry Center, Peking University, Beijing 100871 (P.R. China), Fax: (+86) 10-6276-0890
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Abstract

We report three transformations: 1) direct transformation from biarylmethanols into biarylmethylamines; 2) direct transformation from one biarylmethanol into another biarylmethanol; 3) direct transformation from allylic alcohols into allylic amines. These transformations are based on pyridyl-directed Rh-catalyzed C[BOND]C bond cleavage of secondary alcohols and subsequent addition to C[DOUBLE BOND]X (X=N or O) double bonds. The reaction conditions are simple and no additive is required. The driving force of C[BOND]C bond cleavage is the formation of the stable rhodacycle intermediate. Other directing groups, such as the pyrazolyl group, can also be used although it is not as efficient as the pyridyl group. We carried out in-depth investigations for transformation 1 and found that: 1) the substrate scope was broad and electron-rich alcohols and electron-deficient imines are more efficient; 2) as the leaving group, aldehyde had no significant impact on either the C[BOND]C bond cleavage or the whole transformation; 3) mechanistic studies (intermediate isolation, in situ NMR spectroscopic studies, competing reactions, isotopic labeling experiments) implied that: i) The C[BOND]C cleavage was very efficient under these conditions; ii) there is an equilibrium between the rhodacycle intermediate and the protonated byproduct phenylpyridine; iii) the addition step of the rhodacycle intermediate to imines was slower than the C[BOND]C cleavage and the equilibrium between the rhodacycle and phenylpyridine; iv) the whole transformation was a combination of two sequences of C[BOND]C cleavage/nucleophilic addition and C[BOND]C cleavage/protonation/C[BOND]H activation/nucleophilic addition, with the latter being perhaps the main pathway. We also demonstrated the first example of cleavage of an C(alkenyl)[BOND]C(benzyl) bond. These transformations showed the exchange (or substitution) of the alcohol group with either an amine or another alcohol group. Like the “group transplant”, this method offers a new concept that can be used to directly synthesize the desired products from other chemicals through reorganization of carbon skeletons.

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