Strain and Its Implications in Organic Chemistry

The topic ·Stress and Strain· of this conference was ideally constrasted by the remoteness and quiet atmosphere of the meeting place Hotel Seehof In Ratzeburg, a small medieval town situated on a peninsula in lake "Kuchensee· east of Hamburg In northern Germany. With the participation of 53 leading experts from all over the world, the workshop covered the widest possible range from the advancement of bonding theory, new mechanistic insights into chemical transformations and physical properties of highly strained compounds to their use as building blocks In organic synthesis and even as probes Into the detection of enzyme mechanisms. Because of their specific reactivities small ring units can uniquely play their role in the construction of composite functionalities. Such functionalities can increase the elegance In natural and non-natural products syntheses, since they help to develop more convergent synthetic routes and Improve the necessary chemo-, regio-and stereo-selectivity. This book presents all of the 20 Invited lectures and is complemented with short versions of 12 contributed papers and 13 poster presentations. I am convinced that it will stimulate further rapid development of this field of organic chemistry, which recently has seen extensions into the bioorganic area as well as towards new materials. In fact, several ·supra-natural" -at first sight exotic -compounds are already available In useful quantities and are being exploited to create vastly new molecular devices, i. e. compounds with unprecedented molecular functions and polymers with unconventional properties.

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Proceedings of the NATO Advanced Research Workshop, Ratzeburg, Germany, August 28-September 2, 1988

Contenu
Foreword.- List of Participants.- Some Synthetic Implications of the Concept of Cyclopropyl Units as Pseudo-FunctionalGroups.- Stereoselective Electrocyclizations and Sigmatropic Shifts of Strained Rings : Torquoelectronics!.- The Preparation and Thermal Rearrangement of Functionalized 6-(1-Alkenyl)bicyclo[3.1.0]hex-2-enes. Applications to Synthesis.- Synthesis with Donor-Acceptor-Substituted Vinylcyclopropanes.- Synthesis of Functionalized Episulfides.- Through-Bond Interaction via Cyclobutane Relay Orbitals as a Means of Extending Conjugation.- [2+3]-Carbo- and Heterocyclic Annulation in the Design of Complex Molecules.- Synthetic and Mechanistic Aspects of the Cyclopropene to Vinylcarbene Rearrangement.- Generation and Interception of 1-Oxa-2,3-cyclohexadiene and 1,2,4-Cyclohexatriene.- On the Relationship Between Strain and Chemical Reactivity of Torsionally Distorted Carbon-Carbon Double Bonds.- Photoinduced Single Electron Transfer from Strained Rings.- Chemical Behaviour of Cation Radicals Derived from Strained Molecules in Solution. Spiro-Activation in the Cleavage of Some Arylcyclopropanes upon Treatment with TCNE or DDQ.- The Cyclopropyl Group in Studies of Enzyme-Catalysed Reactions.- Intramolecular [2+2]-Cycloadditions of Ketenes Vaenedn Oslterafins.- Strained Iminium Salts in Synthesis.- The Generation and Rearrangement of 2-Diazocarbonyl Cyclobutanones: The Formation of 5-Spirocyclopropyl-2(5H)furanones.- Computational Studies of Prismane, Helvetane/lsraelane and Asterane.- Cyclobutane-Cyclopentane of Coordinated Adducts of Cycloheptatriene and Tetracyanoethylene via the [2,2]-Sigmahaptotropic Rearrangement.- Quest for Higher Prismanes.- Planarizing Distortions in Polycylic Carbon Compounds.- Strain Release in Aromatic Molecules: The [2n]-Cyclophanes.- Trip around the Three-Membered Cycles Syntheses.- Experimental and Theoretical Studies of Bridged Cyclopropenes.- From Bicyclo[1.1.0] butanes to [n.1.1]Propellanes.- New Aspects of Highly Strained Ring Chemistry.- Strained Cage Systems : Synthetic and Structural Implications.- Studies on the Synthesis of Cyclopentanoic Sesquiterpenes via Rearrangement Routes: (+)Modhephene and (+)lsocumene.- Directionality in Formation of Small Rings by Intramolecular Nucleophilic Substitution.- Synthesis, Chiroptical Properties and Synthetic Applications of Perhydrotriquinacene- 1,4,7-trione.- Reactions of Strained Carbon-Carbon Bonds with Metal Atoms.- Cyclopropabenzenes and Alkylidenecyclopropabenzenes. A Synergistic Relation between Theory and Experiment.- Harnessing Strain: From [1.1.1] Propellanes to Tinkertoys.- Synthesis of Cyclopropenes.- How to get Structures of Strained Compounds: Low Temperature Structures and X-X Electron Deformation Densities.- Novel Intramolecular 1,1 -Cycloadditions of Diazoallenes.- Efficient Route to Optically Active Strained Compounds.- Anionic (3+2)-Cycloreversion of Strained Cage Nitriles.- Reaction of an Angle Strained Cycloheptyne with a Stabilized Stannylene Synthesis and X-Ray Structure of a Distannacyclobutene System.- Structure and Reactivity of Small Heterocycles Containing Germanium Atoms.- Relief of Strain Energy as Driving Force in Ring-Opening Polymerizations of a [1.1.1]Propellane.- Diels-Alder Reactions of Siloxyallylidenecyclopropanes: Facile Syntheses of Spiro- [2.5]octan-3-ones.- Cyclopropyl Group Containing Amino Acids from a-Chlorocyclopropylidenacetates.- Eliminative Fission of Strained Cycloalkoxides - The Question of Electrophilic Catalysis.- Special Reactivity of 8,11-Dihalo[5]metacyclophane.- Small [n]Cyclophanes. Where is the Limit?.