Cobalt Catalysis in Organic Synthesis: Methods and Reactions

Provides a much-needed account of the formidable "cobalt rush" in organic synthesis and catalysis Over the past few decades, cobalt has turned into one of the most promising metals for use in catalytic reactions, with important applications in the efficient and selective synthesis of natural products, pharmaceuticals, and new materials. Cobalt Catalysis in Organic Synthesis: Methods and Reactions provides a unique overview of cobalt-catalysed and -mediated reactions applied in modern organic synthesis. It covers a broad range of homogeneous reactions, like cobalt-catalysed hydrogenation, hydrofunctionalization, cycloaddition reactions, C-H functionalization, as well as radical and biomimetic reactions. First comprehensive book on this rapidly evolving research area Covers a broad range of homogeneous reactions, such as C-H activation, cross-coupling, synthesis of heterocyclic compounds (Pauson-Khand), and more Chapters on low-valent cobalt complexes as catalysts in coupling reactions, and enantioselective cobalt-catalyzed transformations are also included Can be used as a supplementary reader in courses of advanced organic synthesis and organometallic chemistry Cobalt Catalysis in Organic Synthesis is an ideal book for graduates and researchers in academia and industry working in the field of synthetic organic chemistry, catalysis, organometallic chemistry, and natural product synthesis.

Table of Contents:
Preface xiii 1 Introduction to Cobalt Chemistry and Catalysis 1 Marko Hapke and Gerhard Hilt 1.1 Introduction 1 1.2 Organometallic Cobalt Chemistry, Reactions, and Connections to Catalysis 4 1.2.1 Cobalt Compounds and Complexes of Oxidation States +3 to −1 4 1.2.1.1 Co(III) Compounds 5 1.2.1.2 Co(II) Compounds 5 1.2.1.3 Co(I) Compounds 7 1.2.1.4 Co(0) Compounds 8 1.2.1.5 Co(−I) Compounds 9 1.2.2 Bioorganometallic Cobalt Compounds 10 1.3 Applications in Organic Synthesis and Catalytic Transformations 12 1.4 Conclusion and Outlook 19 Abbreviations 20 References 20 2 Homogeneous Cobalt-Catalysed Hydrogenation Reactions 25 Kathrin Junge and Matthias Beller 2.1 Introduction 25 2.2 Hydrogenation of C—C Multiple Bonds (Alkenes, Alkynes) 25 2.3 Hydrogenation of Carbonyl Compounds (Ketones, Aldehydes, Carboxylic Acid Derivatives, CO2) 34 2.3.1 Ketones and Aldehydes 34 2.3.2 Carboxylic Acid Derivatives (Acids, Esters, Imides) 39 2.3.3 Hydrogenation of Carbon Dioxide 47 2.4 Hydrogenation of C—X Multiple Bonds (Imines, Nitriles) 52 2.4.1 Nitrile Hydrogenation 52 2.4.2 Imine Hydrogenation 55 2.4.3 Hydrogenation of N-Heterocycles 56 2.5 Summary and Conclusions 58 2.6 Selected Experimental Procedures 59 2.6.1 Synthesis of Cobalt Complex [(PNHPCy)Co(CH2SiMe3)]BArF4 (8a) 59 Abbreviations 60 References 61 3 Synthesis of C—C Bonds by Cobalt-Catalysed Hydrofunctionalisations 67 Daniel K. Kimand Vy M. Dong 3.1 Introduction 67 3.2 Cobalt-Catalysed C—C Bond Formations via Hydrofunctionalisation 67 3.2.1 Hydroformylation 67 3.2.2 Hydroacylation 68 3.2.3 Hydrovinylation 74 3.2.4 Hydroalkylation 78 3.2.5 Hydrocyanation 80 3.2.6 Hydrocarboxylation 81 3.3 Summary and Conclusions 83 Abbreviations 84 References 85 4 Cobalt-Catalysed C–H Functionalisation 89 Naohiko Yoshikai 4.1 Introduction 89 4.2 Low-valent Cobalt Catalysis 91 4.2.1 C–H Functionalisation with In Situ-Reduced Cobalt Catalysts 91 4.2.1.1 Hydroarylation of Alkynes and Alkenes 91 4.2.1.2 C–H Functionalisation with Electrophiles 98 4.2.1.3 C–H Functionalisation with Organometallic Reagents 103 4.2.1.4 C–H Functionalisation via 1,4-Cobalt Migration 103 4.2.1.5 Hydroacylation 103 4.2.2 C–H Functionalisation with Pincer-Type Ligands and Related Well-Defined Cobalt Catalysts 105 4.3 High-valent Cobalt Catalysis 106 4.3.1 Chelation-Assisted C–H Functionalisation with Cp*CoIII Catalysts 106 4.3.1.1 C—H Addition to Polar C=X Bonds 108 4.3.1.2 Reaction with Alkynes, Alkenes, and Allenes 111 4.3.1.3 Reaction with Formal Nitrene or Carbene Precursors 121 4.3.1.4 Reaction with E–X-type Electrophiles 126 4.3.1.5 Miscellaneous 128 4.3.2 Bidentate Chelation-Assisted C–H Functionalisation with CoIII Catalysts 130 4.3.2.1 Reaction with Alkynes, Alkenes, and Allenes 131 4.3.2.2 Dehydrogenative Cross-coupling Reactions 139 4.3.2.3 Carbonylation and Related Transformations 143 4.3.2.4 Miscellaneous Transformations 144 4.3.3 Miscellaneous 146 4.4 Summary and Outlook 146 Abbreviations 150 References 151 5 Low-valent Cobalt Complexes in C–X Coupling and Related Reactions 163 Céline Dorval and Corinne Gosmini 5.1 Introduction 163 5.2 Cobalt-Catalysed Coupling Reactions with Stoichiometric Organometallic Reagents 163 5.2.1 Cobalt-Catalysed Coupling Reactions with Grignard Reagents 163 5.2.1.1 Csp2— Csp2 Bond Formation 164 5.2.1.2 Csp2— Csp3 Bond Formation 168 5.2.1.3 Csp— Csp2 Bond Formation 173 5.2.1.4 Csp— Csp3 Bond Formation 173 5.2.1.5 Csp3— Csp3 Bond Formation 175 5.2.2 Cobalt-Catalysed Coupling Reactions with Organozinc Reagents 179 5.2.2.1 Csp— Csp2/Csp— Csp3 Bond Formation 179 5.2.2.2 Csp2— Csp2 Bond Formation 181 5.2.2.3 Csp2— Csp3 Bond Formation 183 5.2.2.4 Csp2—CN Bond Formation 186 5.2.2.5 Csp2—CO Bond Formation 186 5.2.3 Carbon–Heteroatom Bond Formation 187 5.2.3.1 C—N Bond Formation 187 5.2.3.2 C—B Bond Formation 188 5.2.4 Cobalt-Catalysed Coupling Reactions with Organoboron Reagents 188 5.3 Cobalt-Catalysed Coupling Reactions with Organomanganese Reagents 192 5.4 Cobalt-Catalysed Coupling Reactions with Copper Reagents 192 5.5 Cobalt-Catalysed Reductive Cross-coupling Reactions 193 5.5.1 Csp2—Csp2 Bond Formation 193 5.5.2 Csp2—Csp2 Bond Formation 196 5.5.3 Couplings with Benzylic Compounds 196 5.5.4 Couplings with Allylic Acetates 197 5.5.5 Csp3—Csp3 Carbon Bond Forming Reactions 197 5.6 Overview and Perspectives 199 5.7 Abbreviations 200 References 201 6 Ionic and Radical Reactions of 𝛑-Bonded Cobalt Complexes 207 Gagik G.Melikyan and Elen Artashyan 6.1 Introduction 207 6.2 Cobalt-Alkyne Complexes: Electrophilic Reactions 209 6.2.1 Intramolecular Diels–Alder Reactions 210 6.2.2 Assembling Tricyclic Ring Systems 211 6.2.3 Assembling Bicyclic Ring Systems: Decalines 212 6.2.4 Assembling Heterocyclic Ring Systems: Benzopyrans 212 6.2.5 Synthesis of Enediynes 213 6.2.6 Assembling Strained Ring Systems 213 6.2.7 Assembling Natural Carbon Skeletons 215 6.3 Cobalt–Alkyne Complexes: Radical Reactions 217 6.4 Cobalt-1,3-enyne Complexes: Electrophilic Reactions 226 6.5 Cobalt-1,3-enyne Complexes: Radical Reactions 228 6.6 Prospects 228 Abbreviations 230 References 230 7 Cobalt-Catalysed Cycloaddition Reactions 235 Gerhard Hilt 7.1 Introduction 235 7.2 Four-Membered Carbocyclic Ring Formation Reactions 235 7.2.1 [2+2] Cycloaddition of Two Alkenes 235 7.2.2 [2+2] Cycloaddition of an Alkene and an Alkyne 237 7.2.3 [2+2] Cycloaddition of Two Alkynes 238 7.3 Six-Membered Ring Formation Reactions 240 7.3.1 Cobalt-Catalysed Diels–Alder Reactions 240 7.3.2 Cobalt-Catalysed [2+2+2] Cycloaddition Reactions Other than Cyclotrimerisation of Alkynes 248 7.3.3 Cobalt-Catalysed Benzannulation Reactions 249 7.4 Synthesis of Larger Carbocyclic Ring Systems 250 7.4.1 [3+2+2] and [5+2] Cycloaddition Reaction 250 7.4.2 [6+2] Cycloaddition Reaction 251 7.5 Conclusions 253 Abbreviations 255 References 255 8 Recent Advances in the Pauson–Khand Reaction 259 David M. Lindsay and William J. Kerr 8.1 Introduction 259 8.2 Advances in the Pauson–Khand Reaction 259 8.2.1 New Methods to Promote the Pauson–Khand Reaction 259 8.2.1.1 Flow Chemistry Applications of the Pauson–Khand Reaction 260 8.2.1.2 New Promoters 261 8.2.2 Novel Substrates 264 8.2.2.1 Maleimides as Alkene Partners 264 8.2.2.2 Novel Enyne Substrates 265 8.2.2.3 Strained Reaction Partners 268 8.3 Asymmetric Pauson–Khand Reaction 269 8.4 Mechanistic and Theoretical Studies 273 8.5 Total Synthesis 276 8.5.1 Synthesis of (+)-Ingenol 276 8.5.2 Towards Retigeranic Acid A 277 8.5.3 The Total Synthesis of Astellatol 278 8.5.4 The Total Synthesis of 2-epi-𝛼-Cedrene-3-one 279 8.6 Summary and Conclusions 280 8.7 Practical Procedures for Stoichiometric and Substoichiometric Pauson–Khand Reactions 281 Abbreviations 282 References 283 9 Cobalt-Catalysed [2+2+2] Cycloadditions 287 Tim Gläsel and Marko Hapke 9.1 Introduction 287 9.2 Reaction Mechanisms of Cobalt-Catalysed Cyclotrimerisations 288 9.3 Cobalt-Based Catalysts and Catalytic Systems 292 9.4 CpCo-Based Cyclisations 296 9.4.1 Carbocyclic Compounds 296 9.4.2 Heterocyclic Compounds 298 9.5 Non-CpCo-Based Cobalt-Catalysed Cyclisations 302 9.5.1 Co2(CO)8-Mediated Cyclisations of Carbocyclic Compounds 302 9.5.2 In Situ-Generated Catalysts and Precatalysts in Carbocyclisations of Alkynes 304 9.5.3 In Situ-Generated Catalysts in the Cyclisation of Alkynes to Heterocyclic Compounds 309 9.6 Cobalt-Mediated Asymmetric [2+2+2] Cycloadditions 313 9.7 Cobalt-Mediated Cyclisations in Natural Product Synthesis 317 9.8 Novel Developments of Cobalt-Mediated Cycloaddition Catalysis 322 9.9 Summary and Outlook 326 9.10 Selected Experimental Procedures 327 9.10.1 Synthesis of [CpCo(CO)(trans-MeO2CCH=CHCO2Me)] (PCAT5) 327 9.10.2 Synthesis of [CpCo(CO){P(OEt)3}] and [CpCo(trans-MeO2CCH=CHCO2Me){P(OEt)3}] (PCAT8) 327 Abbreviations 328 References 330 10 Enantioselective Cobalt-Catalysed Transformations 337 H. Pellissier 10.1 Introduction 337 10.2 Synthesis of Chiral Acyclic Compounds Through Enantioselective Cobalt-Catalysed Reactions 338 10.2.1 Michael and (Nitro)-Aldol Reactions 338 10.2.1.1 Michael Reactions 338 10.2.1.2 (Nitro)-Aldol Reactions 342 10.2.2 Reduction Reactions 346 10.2.2.1 Reductions of Carbonyl Compounds and Derivatives 346 10.2.2.2 Reductions of Alkenes 349 10.2.3 Ring-Opening Reactions 353 10.2.3.1 Hydrolytic Ring-Openings of Epoxides 353 10.2.3.2 Ring-Openings of Epoxides by Nucleophiles Other than Water 356 10.2.4 Hydrovinylation and Hydroboration Reactions 358 10.2.4.1 Hydrovinylations 358 10.2.4.2 Hydroborations 361 10.2.5 Cross-coupling Reactions 363 10.2.6 Miscellaneous Reactions 366 10.3 Enantioselective Cobalt-Catalysed Cyclisation Reactions 370 10.3.1 [2+1] Cycloadditions 370 10.3.2 Miscellaneous Cycloadditions 379 10.3.2.1 (Hetero)-Diels–Alder Cycloadditions 379 10.3.2.2 1,3-Dipolar Cycloadditions 380 10.3.2.3 Other Cycloadditions 383 10.3.3 Cyclisations Through Domino Reactions 386 10.3.4 Miscellaneous Cyclisations 390 10.4 Conclusions 395 Abbreviations 396 References 397 11 Cobalt Radical Chemistry in Synthesis and Biomimetic Reactions (Including Vitamin B12) 417 Michał Ociepa and Dorota Gryko 11.1 Introduction 417 11.2 Cobalt-Mediated Reactions of Carbon-Centred Radicals 417 11.2.1 Homocoupling Reactions 418 11.2.2 Cross-coupling Reactions 420 11.2.3 Additions to Alkenes and Alkynes 423 11.2.4 Cyclisation Reactions 425 11.2.5 Dehalogenation 429 11.2.6 Oxidation 431 11.2.7 Acylation 433 11.2.8 Applications of Cobalt Complexes in Photoredox Catalysis 435 11.2.9 Miscellaneous Reactions 438 11.3 Cobalt-Mediated Reactions of Heteroatom-Centred Radicals 440 11.3.1 Nitrogen-Centred Radicals 440 11.3.2 Other Types of Radicals 441 11.4 Overview and Conclusion 442 11.5 Experimental Section 443 11.5.1 Synthesis of Chloro(pyridine)cobaloxime Co(dmgH)2Cl(py) (116) 443 11.5.2 Synthesis of Aqua(cyano)heptamethyl Cobyrinate (56b) – Hydrophobic Vitamin B12 Model 444 11.5.3 General Procedure for Synthesis of Co(II)(salen) and Co(III)(salen) Complexes 445 Abbreviations 445 References 446 Index 453

About the Author :
Marko Hapke is the Chair of Catalysis at the Johannes Kepler University in Linz, Austria, and also a group leader at the Leibniz Institute of Catalysis e.V. at the University of Rostock, Germany. His research centers on the development of novel cobalt catalysts for [2+2+2] cycloaddition reactions and the understanding of factors determinating reactivity and selectivity. Gerhard Hilt is Full Professor at the Carl con Ossietzky University in Oldenburg, Germany. His research interests are applications of electron-transfer-activated transition-metal complexes in organic synthesis, quantification of Lewis acidities, organic electrochemistry, and surface-assisted transformations.