Until the early seventies, tautomeric i. e. fast and reversible rearrangement reactions accompanied by migrations of carbon-centered groups - were practi­ cally unknown. For a long time it was assumed that the family of tautomeric reactions was confined to proto tropic transformations only. However, the discovery in the fifties of the reversible metallotropic rearrangements showed the domain of migratory tautomerism to be substantially broader. The synthesis of the metallotropic compounds was based on the substitution of a proton in prototropic compounds by an organometallic group. This approach rarely proved fruitful when attempting to effect tautomeric rearrangements of organic and organometallic groups formed by the elements to the right of carbon in the Periodic Table. By contrast, a novel approach involving an analysis of the steric requirements inherent in the structure of the transition state of a reactive center and an examination of the stereodynamic possibilities has given rise to a target-oriented molecular design of compounds capable of rapid and reversible intramolecular migration of the type indicated. The implementation of this ap­ proach, which is the subject of the present book, has already led to the preparation of new tautomeric compounds in which such heavy organic migrants as acyl, aryl, sulfinyl, phosphoryl, arsinyl, and other groups migrate in molecules at a frequency 6 9 of 10 -10 S-I at ambient temperature, i. e., at the rates comparable with protonic migrations.

Inhaltsangabe1. The Problem of Tautomerism.- 1. Tautomerism as Dynamic Isomerism.- 1.1. Molecular Structure and Isomerism.- 1.2. Bond Rupture Formation Criterion.- 1.3. Tautomerism and Rearrangements.- 1.4. Thermodynamic and Activational Scale of Tautomeric Processes.- 2. Degenerate Tautomerism.- 3. Methods for Investigating Tautomeric Systems.- 4. Butlerov's and Laar's Tautomeric Systems.- 5. Tautomerism and the Mechanisms of Organic Reactions.- 6. Classification of Tautomeric Reactions.- 6.1. Prototropy.- 6.2. Metallotropy.- 6.2.1. ?, ?-Transfers.- 6.2.2. ?, ?-Transfers.- 6.2.3. ?, ?-Transfers.- 6.3. Anionotropy.- 6.4. Valence Tautomerism.- 6.4.1. ?-Valence Tautomerism.- 6.4.2. ?, ?-Valence Tautomerism.- 6.4.3. ?-Valence Tautomerism.- 7. Conclusion.- References.- 2. Carbonotropy.- 1. The Problem of Carbonotropy.- 1.1. General Principles.- 1.2. Choice of a Migrant.- 2. Sigmatropic Acyl and Aryl Rearrangements.- 2.1. Acyl 1,3-Rearrangements.- 2.2. Aryl 1,3-Rearrangements.- 2.3. 1,5-and 1,7-Acyl Rearrangements.- 3. Acylotropic Tautomerism.- 3.1. Tautomeric 1,3-Acyl Rearrangements of the N,N?-diarylamidine Derivatives.- 3.2. Stereochemistry of Acyl Migration.- 3.3. Tautomeric 1,5-Acyl Rearrangements of O-Acylenols of 1,3-Diketone.- 3.4. Acylotropy of 9-Acyloxyphenalen-l-ones.- 3.5. Tautomerism of 2-Acyloxytropones.- 4. Tautomeric Rearrangements of Aryl Groups.- 4.1. 1,3-Rearrangements of Aryl Groups.- 4.2. O,O?-Migrations of the Aryl Groups in O-Aryl Derivatives of Tropolone and the Synthesis of Bipolar Spiro- ?-Complexes.- 4.3. Valence Tautomerism of O-Aryl Ethers of o-Hydroxybenzaldehydes and their Imines.- 5. Carbonotropic Tautomerism in Ions, Radicals and Cyclopolyenes.- 5.1. Acylotropic and Arylotropic Rearrangements in Anions.- 5.2. Acylotropy in Phenoxyl Radicals.- 5.3. Tautomeric Rearrangements of Carbocations.- 5.4. Acyl and Aryl Migrations in Cyclopolyenes.- References.- 3. General Principles of the Design of Tautomeric Systems.- 1. Possibilities of Quantum Mechanical Prediction of Tautomeric Reactions.- 1.1. Theoretical Evaluation of Free Energies of Tautomeric Equilibria.- 1.2. Theoretical Calculation of Activation Energies of Tautomeric Reactions.- 2. Stereochemical Approach to the Design of Tautomeric Compounds.- 2.1. Intramolecular Coordination of the Migrating Group.- 2.2. Cyclic Electron Transfer in the Sigmatropic Reaction and Multigraphs of Tautomeric Systems.- 2.3. Orbital Symmetry and Activation Barriers of Sigmatropic Shifts between Heteroatomic Centers.- 2.4. Steric Demands of the Transition State Structures.- 2.4.1. The Bond Configuration of the Central Atom.- 2.4.2. Structure of the Molecular System Connected with a Migrant.- 2.4.3. Addition-Rearrangement-Elimination (AdRE) Mechanism.- 2.5. Analogy in Steric Requirements between Fast Intramolecular, Enzymic and Topochemical Reactions.- References.- 4. The Mechanisms of Nucleophilic Substitution at the Main Group Element and Design of Intramolecular Tautomeric Systems.- 1. Tautomeric Rearrangements of Carbon-containing Groups.- 1.1. Alkyl Transfers.- 1.1.1. Alkyl Rearrangements.- 1.1.2. Stereochemistry of Nucleophilic Substitution Reactions at the sp3-hybridized Carbon Atom.- 1.1.3. Alkyl Migrations with Retention of Configuration at the sp3-carbon Atom.- 1.2. Vinylotropic Tautomerism.- 2. Silylotropic Tautomerism.- 3. Tautomeric Migrations of Phosphorus-containing Groups.- 3.1. PIV-Migrants.- 3.2. PIII-Migrants.- 3.3. PV-Migrants.- 4. Tautomeric Rearrangements of As-containing Groups.- 5. Tautomeric Rearrangements of Sulfur-containing Groups.- 5.1. SII-Migrants.- 5.2. SIII-Migrants.- 5.3. SIV-Migrants.- References.- 5. Dyotropic and Polytropic Tautomeric Systems.- 1. Scope and Definition.- 2. The Mechanism and Energetics of the Dyotropic Reactions.- 2.1. Concerted and Nonconcerted Dyotropic Rearrangements.- 2.2. Multigraphs of Dyotropic and Polytropic Systems.- 2.3. Quantum Mechanical Studies on the Mechanism of Dyotropic Reactions.- References.- 6. Dissociative and