Table of Contents

List of Contributors XI

Preface XV

1 Synthesis of Dendralenes 1
Nicholas J. Green,Mehmet F. Saglam, andMichael S. Sherburn

1.1 Introduction 1

1.2 Multibond Forming Processes 2

1.2.1 Double Alkenylation Reactions 2

1.2.2 Double Alkenation Reactions 4

1.2.3 Other Multibond Forming Processes 10

1.3 Solo-Bond-Forming Reactions 15

1.3.1 C1–C2 Alkenation Reactions 15

1.3.2 C2–C3 Alkenylation Reactions 17

1.3.3 C3–C3′ Alkenation Reactions 25

1.4 Dendralenes from Dendralenes 28

1.5 Functional Group Interconversion Reactions 31

1.6 Concluding Remarks 32

References 32

2 The Diene-Transmissive Hetero-Diels–Alder Reaction 39
Takao Saito and Noriki Kutsumura

2.1 Introduction 39

2.2 DTHDA Reaction of Heterotrienes 41

2.2.1 DTHDA Reaction of Thiatrienes 41

2.2.2 DTHDA Reaction of Oxatrienes 42

2.2.3 DTHDA Reaction of Azatrienes 46

2.2.4 DTHDA Reaction of Dioxatrienes as Masked Oxathiatrienes and Oxazatrienes 51

2.3 DTHDA Reaction with Heterodienophiles 52

References 56

3 The Nazarov Cyclization of Cross-Conjugated Ketones 59
Louis Barriault and Mathieu Morin

3.1 Introduction 59

3.2 Mechanism 59

3.3 Substituent Effects 60

3.3.1 α-Substituents 60

3.3.1.1 Steric Hindrance 60

3.3.1.2 Electron-Donating Substituents 61

3.3.1.3 Electron-Withdrawing Substituents 62

3.3.2 β-Substituents 63

3.3.2.1 Steric Hindrance 63

3.3.2.2 Electron-Donating Substituents 65

3.3.3 Torquoselectivity 65

3.3.3.1 Silyl Groups as Traceless Substituents 66

3.3.3.2 Allenyl Alkenyl Ketones 67

3.3.3.3 Chirality Transfer 68

3.3.3.4 Catalysis of the Nazarov Reaction 69

3.4 Interrupted Nazarov Reactions 73

3.4.1 Cascade Cyclizations 73

3.4.2 [3+2]- and [4+3]Cycloadditions of the Oxyallyl Cation 74

3.4.3 Intermolecular Trapping of the Nazarov Intermediate 75

References 78

4 [n]Radialenes 79
Gerhard Maas

4.1 Introduction 79

4.2 Syntheses and Reactivity 80

4.2.1 [3]Radialenes 81

4.2.2 [4]Radialenes 89

4.2.3 [5]Radialenes 97

4.2.4 [6]Radialenes 98

4.2.5 Higher [n]Radialenes and Radialene Substructures in Polycyclic Conjugated π-Systems 105

4.3 Structural and Bonding Properties 107

References 111

5 Oxocarbons, Pseudo-oxocarbons, and Squaraines 117
Vanessa E. de Oliveira, Renata Diniz, Flávia C. Machado, and Luiz Fernando C. de Oliveira

5.1 Introduction 117

5.2 Oxocarbons and Coordination Chemistry 121

5.3 Pseudo-oxocarbons 128

5.3.1 Squaraines 132

5.4 Conclusion and Outlook 139

References 139

6 Recent Developments in Fulvene and Heterofulvene Chemistry 145
Takeshi Kawase and Hiroyuki Kurata

6.1 Introduction 145

6.2 Triafulvenes 148

6.2.1 Benzotriafulvene and Related Compounds 149

6.2.1.1 Synthesis 149

6.2.1.2 Reactions of Benzotriafulvenes 149

6.2.2 Triafulvalene and Related Compounds 150

6.2.2.1 Synthesis of Benzotriafulvalenes 150

6.2.2.2 Triafulvalenes 151

6.2.2.3 Cyclic Bicalicenes 151

6.2.3 Heterotriafulvenes 152

6.2.3.1 Cyclopropenones (CPNs) 152

6.2.3.2 Reaction of CPNs and Related Compounds 154

6.2.3.3 Cyclopropenone Imides (Azatriafulvenes) 159

6.2.3.4 The Other Heterotriafulvenes 159

6.3 Pentafulvenes and Related Compounds 162

6.3.1 Pentafulvenes 162

6.3.1.1 Synthesis of Pentafulvenes 162

6.3.1.2 Reactions of Pentafulvenes 175

6.3.2 Pentafulvalenes 179

6.3.2.1 Synthesis of Symmetric Benzofulvalenes 179

6.3.2.2 Synthesis of Asymmetric Benzofulvalenes 182

6.3.3 Synthesis of Pentafulvenes as Functional Dyes 183

6.3.3.1 6,6-Dicyanofulvenes 183

6.3.3.2 1,3-Dithiafulvalenes 186

6.3.4 Fused Ring Systems Involving Pentafulvene Moieties 187

6.3.4.1 Dibenzopentalenes 191

6.3.4.2 Indacenes 196

6.3.4.3 Heterocyclic Systems 198

6.3.4.4 Carbaporphyrinoids 201

6.3.4.5 Reactions of Fulvalenes for the Construction of Fullerene Fragments 202

6.3.5 Cyclopentadienones (Oxapentafulvene) 205

6.3.5.1 Synthesis of CPDN 207

6.3.5.2 Reaction of CPDNs 219

6.3.6 Heterofulvenes 222

6.3.6.1 Azafulvenes 222

6.3.6.2 Silafulvene 223

6.3.6.3 Phosphafulvene 224

6.4 Heptafulvenes 225

6.4.1 Synthesis of Heptafulvenes 226

6.4.1.1 Synthesis of Dihydroazulene/Vinylheptafulvene (DHA/VHF) Systems 226

6.4.1.2 Reaction of 2H-Cyclohepta[b]furan-2-one Derivatives 228

6.4.2 Heteroheptafulvenes 233

6.4.2.1 Thiatropone (Tropothione) 233

6.4.2.2 Azaheptafulvenes 234

6.5 Other Fulvenes 235

References 236

7 ConstructingMolecular Complexity and Diversity by Cycloaddition Reactions of Fulvenes 249
Bor-Cherng Hong

7.1 Introduction 249

7.2 Reactions of Pentafulvenes 250

7.2.1 [2+2]Cycloadditions 250

7.2.2 [2+3]Cycloadditions 251

7.2.3 [2+4]Cycloadditions 253

7.2.4 [2+8]Cycloadditions 258

7.2.5 [4+2]Cycloadditions 258

7.2.6 [4+3]Cycloadditions 266

7.2.7 [6+2]Cycloadditions 267

7.2.8 [6+3]Cycloadditions 269

7.2.9 [6+4]Cycloadditions 277

7.2.10 Miscellaneous Reactions 280

7.3 Reactions of Heptafulvenes 280

7.4 Reactions of Triafulvenes 284

7.5 Conclusions 296

Acknowledgments 296

References 296

8 Cross-Conjugation and Electronic Structure in TTF Analogs 301
Masashi Hasegawa and Yohji Misaki

8.1 Introduction 301

8.2 Dendralene-Type TTF Analogs and Related Compounds 302

8.2.1 [n]Dendralenes (n=3,4) with DT Units 302

8.2.2 Analogs of DT [n]Dendralenes 305

8.2.3 Thienylene-Inserted DT[n] Dendralenes and Related Compounds 307

8.2.4 Tris-Fused TTF Analogs Possessing [3]Dendralene Moieties 313

8.3 Radialene-Type TTF Analogs (DT-Substituted Radialenes) 314

8.3.1 [4]- and [6]Radialenes with DT Rings 315

8.3.2 [5]Radialene with DT Rings 317

8.3.3 Extended [5]radialenes 320

8.4 Cross-Conjugated TTFs and Related Compounds Linked by π-Systems 323

8.4.1 TTFs in Cross-Conjugated Systems 323

8.4.2 Acetylene-Extended Tetrathiafulvalenes in Cross-Conjugated Systems 326

8.4.3 Acetylene-Extended Radialenes and Dendralenes 328

8.4.4 Cross-Conjugated Systems in Acetylene-Extended Radiaannulene Frameworks 329

References 333

9 Cross-Conjugation in Expanded Systems 337
Christian Richard Parker and Mogens Brøndsted Nielsen

9.1 Introduction 337

9.2 Tetrathiafulvalene and Dithiafulvene 338

9.2.1 Oligomers by Dithiafulvene Oxidation 339

9.2.2 Anthraquinone-Extended Tetrathiafulvalenes 339

9.3 Communication between Two Identical Redox Centers 340

9.3.1 Organic Redox Centers 342

9.3.2 Organometallic Redox Centers 344

9.3.3 Expanded Radiaannulenes and Radialenes 346

9.4 Cross-Conjugation and Optical Properties 349

9.4.1 Nitrophenolates 350

9.4.2 Other Donor–Acceptor Systems 351

9.4.3 Extended Tetrathiafulvalenes and Dithiafulvene-Dendralenes 352

9.4.4 Synthesis of Dithiafulvene-Dendralene Oligomers by Cascade Reactions 353

9.4.5 Photoinduced Charge Separation in a Donor–Acceptor System 354

9.5 Conjugation and Molecular Electronics 355

9.5.1 Theoretical Comparison of Conduction Pathways 355

9.5.2 Meta- versus Para-Anchoring 356

9.5.3 The Dithienylethene Photoswitch 357

9.5.4 Hydroquinone–Quinone Redox Switch 357

9.5.5 Oligo(phenyleneethynylene)-Tetrathiafulvalene Cruciform Redox Switch 358

9.6 Conclusions 359

References 361

10 Transition Metal Complexes of Cross-Conjugated 𝛑 Systems 365
Holger Butenscḧon

10.1 Introduction 365

10.2 Trimethylenemethane Complexes 365

10.3 Fulvene Complexes 372

10.4 Fulvalene Complexes 380

10.5 Azulene Complexes 385

10.6 Pentalene and Acepentalene Complexes 387

10.7 Various Complexes 389

References 391

11 Cross-Conjugation and Quantum Interference 397
Gemma C. Solomon

11.1 Introduction 397

11.2 Molecular Electron Transport 398

11.3 The Transport Properties of Cross-Conjugated Molecules 401

11.4 Understanding and Predicting Interference 405

11.5 More than Topology 409

11.6 Conclusions 410

References 411

12 Cross-Conjugation in Synthesis 413
Christopher G. Newton andMichael S. Sherburn

12.1 The Rapid Generation of Structural Complexity 413

12.2 Diene-Transmissive Diels–Alder Reactions 413

12.3 [3]Dendralenes 416

12.3.1 Classification 416

12.3.2 Acyclic [3]Dendralenes 417

12.3.3 Cyclic [3]Dendralenes 422

12.4 Higher Dendralenes 428

12.5 Applications 433

12.6 The Radialenes 435

12.7 Concluding Remarks 440

References 441

Author Index 445

Subject Index 451

About the Author

Born in 1940, Henning Hopf was Director of the Institute for Organic Chemistry at the TU Braunschweig. After studying chemistry in Gottingen and at the University of Wisconsin in Madison, where he gained his doctorate 1967, he qualified as a professor in 1972 at the University of Karlsruhe. Three years later he was offered a position at the University of Wurzburg and from there followed an offer of a professorship at Braunschweig in 1979 from which he retired in 2006. His main areas of research concern hydrocarbon chemistry (alkynes, allenes, cumulenes, aromatic compounds, cyclophanes, polyolefines, etc.) and mechanistic investigations of high-temperature reactions. For his scientific oeuvre he is received many national and international awards. He served as the President of the German Chemical Society (GDCh) whose Honorary Member he is.

Born in 1966, Michael Sherburn is Professor of Chemistry at the Research School of Chemistry at the Australian National University in Canberra, Australia. He studied chemistry first at The University of Nottingham, from where he obtained his PhD degree in 1991, then as a postdoctoral fellow at the Australian National University. He held positions at Massey University in New Zealand and The University of Sydney before returning to the Research School of Chemistry in 2002. His research interests focus on the development of efficient synthetic methods, strategies and tactics for the synthesis of natural and unnatural structures.