Electrocyclic Reactions

Transcription

1 Farzana Latif Ansari, Rumana Qureshi, Masood Latif Qureshi Electrocyclic Reactions From Fundamentals to Research WILEY-VCH Weinheim New York Chichester Brisbane Singapore Toronto

2 Preface Acknowledgements Foreword v vii ix 1. Pericyclic Reactions General Features Classification Electrocyclic Transformations Sigmatropic Rearrangements Cycloaddition Reactions Cheletropic Reactions Group Transfer Reactions Analysis Orbital Symmetry Conservation Frontier Orbitals Approach Möbius-Hückel Approach Theoretical and Computational Approach Significance References Electrocyclic Transformations Mechanism Thermal Electrocyclizations [1,3] Electrocyclic Reactions [1,4] Electrocyclic Reactions [1,5] Electrocyclic Reactions Isoelectronic Exchange Isoionic Exchange [1,6] Electrocyclic Reactions Photochemical Electrocyclizations Electrocyclizations of Radicals and Radical Ions Metal Catalysis References 55

3 Xll 3. Orbital Symmetry Conservation Basic Concepts Conrotation and Disrotation Orbital Symmetry Symmetry Conservation Disrotatory Cyclization Conrotatory Cyclization Applications Energy Level Correlation Analysis Even-Electron Systems Odd-Electron Systems Symmetry State Correlation Analysis Even-Electron Systems Odd-Electron Systems Limitations References Frontier Orbitals Approach Basic Concepts Interactions between Orbitals Atomic Orbitals Molecular Orbitals Suprafacial and Antarafacial Geometries Applications Cycloadditions Electrocyclizations Thermal Photochemical Generalized Selection Rules Odd-SumRule Odd-EvenRule References Möbius-Hückel Approach Basic Concepts Hückel Systems HMO Relationship Energy Level Patterns Möbius Systems Ground State Examples Energy Level Patterns 172

4 xm 5.2 Applications Thermal Reactions Photochemical Reactions Summary References Theoretical and Computational Approach Study of Reaction Paths Even-Electron Systems [1,3] Electrocyclic Reactions [ 1,4] Electrocyclic Reactions [1,5] Electrocyclic Reactions [1,6] Electrocyclic Reactions [ 1,8] Electrocyclic Reactions Odd-Electron Systems Ring Opening of Cyclopropyl Radical Electrocyclic Reactions of Bicycloalkyl Radicals Stereoselectivity in Electrocyclic Reactions Experimental Aspect Experimental Observations Interpretation of Experimental Activation Energy Data Theoretical Aspect Interpretation of Theoretical Activation Energy Data Theoretical Explanation of Stereoselectivity References 232 Appendix A. Molecular Orbital Theory 235 A. 1. Basic Concepts of Quantum Mechanics 235 A The Schrödinger Equation 235 A. 1.2 Atomic Orbitals 236 A.2. Difference Between MO and VB Theories 237 A.3. Mathematical Formulation of Molecular Orbital Theory 238 A.3.1. LCAO Approach 23 8 A.3.2. Shapes and Energies of MOs 240 A.3.3. Different MO Methods 241 A.4. Hückel Molecular Orbital Method 242 A.4.1. Limitations and Assumptions of HMO Method 242 A.4.2. Applications of HMO Method 243 A Ethylene 243 A Allyl System 244 A Butadiene 245

5 XIV A.4.4. EHMO Method 249 A.5. SCFMethods 250 A.5.1.RHF Method 250 A.5.2. UHF Method 250 A.6. ab initio Methods 251 A.7. Configuration Interaction 251 A.7.1. Electronic Configuration and Electronic States 251 A.7.2. Schemes for Configuration Interaction 253 A.8. References 254 Appendix B. Symmetry Classification of Molecules 255 B.l. Symmetry Elements 256 B Centre of Symmetry 256 B Rotation Axis of Symmetry 256 B.1.3. Plane of Symmetry 257 B Rotation-Reflection Axis of Symmetry 259 B.1.5.Identity 259 B.2. Point Groups 261 B.2.1. Schönflies Notations 261 B.2.2. Establishing the Molecular Point Group 266 B.3. References 268 Index 269