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Rhodium-Catalyzed Direct C-H Functionalizations of Sulfoximines and Copper-Catalyzed Enantioselective Synthesis of Dihydropyrazoles

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Rhodium-Catalyzed Direct C-H Functionalizations of Sulfoximines and Copper-Catalyzed Enantioselective Synthesis of Dihydropyrazoles Rhodium-Catalyzed Direct C-H Functionalizations of Sulfoximines and Copper-Catalyzed Enantioselective Synthesis of Dihydropyrazoles Von der Fakultät für Mathematik, Informatik und Naturwissenschaften der RWTH Aachen University zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften genehmigte Dissertation vorgelegt von Master of Science Wanrong Dong aus Lu’an, China Berichter: Universitätsprofessor Dr. rer. nat. Carsten Bolm Universitätsprofessor Dr. rer. nat. Markus Albrecht Tag der mündlichen Prüfung: 28.05.2014 Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar. The work presented in this thesis was carried out from October 2009 until December 2013 at the Institute of Organic Chemistry, RWTH Aachen University, under the supervision of Professor Dr. Carsten Bolm, also many thanks to my second examiner Prof. Dr. Markus Albrecht. Part of this work has already been published: Rhodium-Catalyzed Oxidative Annulation of Sulfoximines and Alkynes as an Approach to 1,2-Benzothiazines. W. R. Dong, L. Wang, K. Parthasarathy, F. F. Pan, C. Bolm*, Angew. Chem. Int. Ed. 2013, 52, 11573. Enantioselective Synthesis of Dihydropyrazoles by Formal [4+1] Cycloaddition of in Situ-Derived Azoalkenes and Sulfur Ylides. J. R. Chen, W. R. Dong, M. Candy, F. F. Pan, M. Jörres, C. Bolm*, J. Am. Chem. Soc. 2012, 134, 6924. Acknowledgements I would like to thank Prof. Dr. Carsten Bolm for the interesting research topic, excellent support and working conditions in the group. I would also like to thank the China Scholarship Council (CSC) for the coverage of predoctoral stipend in RWTH Aachen University. I appreciate to my parents (董照才，慈书存), my fiancée Jing Tang (汤婧) and her parents (汤立明，陈菊香) for the continuous understanding, support and love to me. Also I should thank my uncle Zhaocang Dong(董照仓), my elder cousin brother Jiangning Dong (董江宁) and other relatives for their generous assistance. I am grateful to Mrs. Ingrid Voss and Dr. Ingo Schiffers for the considerate help all the way during my stay in Aachen. Many thanks to Dr. Kanniyappan Parthasarthy for the selfless instructions. Words cannot express my gratitude to Zhenjiang Liu, Lianghua Zou, Long Wang, Huijun Zhang (Meg), Xiaoyun Chen, Jiarong Chen, Zhibing Dong, Jiang Cheng, Jun Wang, Ying Cheng, Hanchao Cheng, Shunxi Dong Eduard Benetzkij and all the other colleagues who have accompanied me for the last four and half years in Aachen. Table of Content Table of Content Chapter 1 Rhodium-Catalyzed Direct C-H Functionalization of Sulfoximines Part I Introduction……………………………………………………………………1 1 Introduction of Transition Metal-Catalyzed Direct C-H Bonds Functionalization.1 1.1 Rhodium-Catalyzed C-H Activations and Subsequent Annulation Reactions...2 1.2 Rhodium-Catalyzed Addition Reactions………………………….………….11 2 General Introduction of Sulfoximines and Metal-catalyzed Synthesis of N-Substituted Sulfoximines…………………………………………………….19 2.1 General Introduction of Sulfoximines………………………………………..19 2.2 Synthesis of N-Substituted Sulfoximines by Metal-Catalysis……………….21 Part II Rhodium-catalyzed Annulation Reaction of Sulfoximines and Alkynes……28 1 Research Objective………………………………………………………………28 2 Results and Discussions…………………………………………………………29 2.1 Optimization of Annulation Reaction of Sulfoximines with Alkynes………..29 2.1.1 Screening on Transition Metal Catalysts………………………………….29 2.1.2 Effect of Solvents…………………………………………………………31 2.2 Substrate Scope………………………………………………………………32 2.3 Mechanistic Investigation…………………………………………………....35 2.4 Oxidative Cleavages of 1,2-Benzothiazines…………………………….……37 3 Summary………………………………………………………………………...38 4 Experimental Part………………………………………………………………..39 4.1 General Information………………………………………………………….39 4.2 General Procedure for the Synthesis of 1,2-Benzothioazines………………..39 4.3 Synthesis of Sulfoximine 60a-d1……………………………………………..40 4.4 Intramolecular Kinetic Isotope Effect (KIE)…………………………………40 4.5 Synthesis of Rhodacycles II and II’………………………………………….41 4.6 Reactions of Rhodacycles II and II’ with Alkyne 2a…………………………41 4.7 Oxidative Cleavages of 1,2-Benzothiazines………………………………….42 I Table of Content 5 Data and Characterization……………………………………………………….42 Part III Rhodium-Catalyzed Sulfoximine-Directed ortho-C-H Addition Reaction...59 1 Research Objective………………………………………………………………59 2 Results and Discussions…………………………………………………………60 3 Substrate Scope………………………………………………………………….61 4 Summary………………………………………………………………………...63 5 Experimental Part………………………………………………………………..64 6 Data and Characterization……………………………………………………….64 Chapter 2 Enantioselective Synthesis of Dihydropyrazoles by Formal [4+1] Cycloaddition of in Situ-Derived Azoalkenes and Sulfur Ylides 1 General Introduction……………………………………………………………..75 1.1 General Introduction of Dihydropyrazole Compounds………………………75 1.1.1 Diazoalkanes as Substrates for Pyrazoles by [3+2] Cycloadditions……...76 1.1.2 Azomethine Imines as Substrates for Pyrazoles by [3+2] Cycloadditions.79 1.1.3 Nitrile Imines as Substrates for Pyrazoles by [3+2] Cycloadditions……..81 1.1.4 Hydroxylamines and Hydrazines as Substrates for Pyrazoles by [3+2] Cycloadditions…………………………………………………………....83 1.1.5 Introduction of the Formal [4+1] Cycloaddition Reactions………………85 1.1.6 Introduction of Sulfur Ylides……………………………………………...86 2 Research Objective……………………………………………………………....87 3 Results and Discussions…………………………………………………………89 3.1 Screening on Metal Catalysts………………………………………………...89 3.2 Screening on Ligands………………………………………………………...90 3.3 Substrate Scope………………………………………………………………92 4 Summary………………………………………………………………………...98 5 Experimental Part………………………………………………………………..98 6 Data and Characterization……………………………………………………….99 Reference……………………………………………………………………………127 Appendix……………………………………………………………………………133 II Chapter 1 Rhodium-Catalyzed Direct C-H Functionalizations of Sulfoximines Chapter 1 Part 1 Introduction 1 Introduction of Transition Metal-Catalyzed Direct C-H Bonds Functionalizations The carbon-hydrogen bonds (abbreviated as C-H bonds) are fundamental and most common chemical bonds in a variety of organic compounds. Owing to the high bond dissociation energy and the inertness of C-H bonds,[1] e.g., 105 kcal/mol for H-CH3 and 110 kcal/mol for H-C6H5, transformations of inert C-H bonds into C-C bonds or C-X bonds (X= S, O, N, Cl, Br, etc.) by metal catalysis are still great challenges nowadays. In general, traditional approaches for the transformations of C-H bonds rely on prefunctionalized starting materials for both reactivity and selectivity or require costly chemical steps. Thus, the development of a cheap and alternative method is still desirable to address the above issues. Transition metal-catalyzed direct functionalization of inert C-H bonds has attracted great attention and gradually emerged as a powerful method in organic synthesis. Compared with conventional approaches, the methodologies are environmental friendly and atom-economical and have been frequently applied in the synthesis of natural products, biologically active molecules and organic materials. In general, directing group-assisted transition metal-catalyzed C-H bond activation involves a five-membered cyclometalated key intermediate A (Scheme 1), which provides a favorable driving force in inducing reactivity at the desired location. Various directing groups have been utilized to activate C-H bonds by aid of transition metal catalysts, such as ruthenium, rhodium, palladium, iridium and other metal catalysts. 1 Chapter 1 Scheme 1 General mechanism for directing group-assisted ortho-C-H activation Among all the transition metal catalysts, rhodium complexes are sustainable metal catalysts in the field of C-H activations. Despite the general high cost of rhodium complexes, rhodium catalysis will still be highly desirable if reaction systems are inaccessible under palladium or ruthenium catalysis. Indeed, the past decades have witnessed a dramatic development in the field. Rhodium-catalyzed directing group-assisted C-H activations and successive functionalization protocols have been * extensively investigated. Very recently, rhodium(III) complexes, such as [RhCp Cl2]2, * * [Cp Rh(MeCN)3][BF4]2 and [Cp Rh(MeCN)3][SbF6]2 have proved to be highly efficient catalysts in the field of direct C-H bonds functionalization. In this chapter, we will focus on rhodium-catalyzed C-H activations and subsequent functionalization reactions. 1.1 Rhodium-Catalyzed C-H Activations and Subsequent Annulation Reactions Within the past decades, the oxidative activations of C-H/N-H or C-H/O-H bonds and subsequent annulation reactions with alkynes or alkenes have emerged as powerful methods for the synthesis of heterocyclic or carbocyclic compounds in metal-catalyzed organic synthesis. In general, these reactions proceed by chelation-assisted C-H bonds activations and oxidative additions of metal complexes to the ortho-C-H bonds, insertion of the alkynes or alkenes, reductive eliminations, and then annulations. These protocols have been utilized extensively for the 2 Chapter 1 preparation of a wide range of substituted heterocyclic compounds such as indoles, isocumarines, isoquinolines, carbazoles, benzothiazoles and pyridines. In this part we will focus on Rh(III)-catalyzed annulation reactions and the involved mechanisms. Satoh and Miura firstly reported a synthesis of polyarylated naphthyl and anthryl azole derivatives by direct coupling of phenyl azoles with internal alkynes in the presence of a rhodium catalyst and a copper oxidant (Scheme 2). The reaction involved the multiple C-H bonds cleavages and
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