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Optically active 2,5-disubstituted bicyclo[2.2.2]octa-2,5-dienes (bod) have found use within synthetic organic chemistry as chiral ligands for rhodium asymmetric catalysis reactions. These chiral ligands often provide greater enantioselectivity than their phosphorus-based chiral ligand cousins when employed in the formation of carbon-carbon bonds under rhodium catalysis. The drawback to using these types of 2,5-disubstituted bicyclo[2.2.2]octa-2,5-diene ligands is that they are very expensive to buy if they are commercially available or they must be synthesized if they are not commercially available. Present literature syntheses of these bod ligands rely on the physical separation of diastereomeric derivatives via recrystallization with low recovery or the separation of enantiomers via chiral HPLC, in which only small amounts of material may be separated. We have devised a synthesis of phenyl, benzyl, and methyl substituted bod ligands based on a bridged Robinson annulation reaction of 1,5-diketones and 1,5-ketoaldehydes, which gives the bicyclic core necessary for the bod ligand. Furthermore, our synthesis is designed to create optically active 1,5-diketones and 1,5-ketoaldehydes which transfer their chirality to the bicyclic core of the molecule. Our synthesis does not rely upon separation of racemic material at any step; instead we provide a method to synthesize any optically active bod ligand that is desired. We successfully synthesized the chiral 3-allylcyclohexanone (>95% ee), a key intermediate in our synthesis, using a chiral conjugate allylation of & alpha;, & beta;-unsaturated & beta;-ketoesters using Cu(OTf)2 and the chiral tBu-box ligand. We then successfully completed the racemic synthesis of 2,5-diphenylbicyclo[2.2.2]octa-2,5-diene (Ph-bod) over 11 steps in 4.4% yield. The chiral Ph-bod ligand is projected to take 14 steps and proceed in a 1.1% overall yield. We also synthesized the racemic 2,5-bis(phenylmethyl)bicyclo[2.2.2]octa-2,5-diene (Bn-bod) over 7 steps in 1.4% overall yield. The synthesis of 2,5-dimethylbicyclo[2.2.2]ocat-2,5-diene (Me-bod) was attempted but was unsuccessful at this time. Ultimately we proved the utility of the bridged Robinson annulation reaction for the synthesis of various bicyclo[2.2.2]octa-2,5-dienes.
Barry Trost: Transition metal catalyzed allylic alkylation.- Jeffrey W. Bode: Reinventing Amide Bond Formation.- Naoto Chatani and Mamoru Tobisu: Catalytic Transformations Involving the Cleavage of C-OMe Bonds.- Gregory L. Beutner and Scott E. Denmark: The Interplay of Invention, Observation and Discovery in the Development of Lewis Base Activation of Lewis Acids for Catalytic Enantioselective Synthesis.- David R. Stuart and Keith Fagnou: The Discovery and Development of a Palladium(II)-Catalyzed Oxidative Cross-Coupling of Two Unactivated Arenes.- Lukas Gooßen and Käthe Gooßen: Decarboxylative Cross-Coupling Reactions.- A. Stephen K. Hashmi: Gold-Catalyzed Organic Reactions.- Ben List: Developing Catalytic Asymmetric Acetalizations.- Steven M. Bischof, Brian G. Hashiguchi, Michael M. Konnick, and Roy A. Periana: The De NovoDesign of CH Bond Hydroxylation Catalysts.- Benoit Cardinal-David, Karl A. Scheidt: Carbene Catalysis: Beyond the Benzoin and Stetter Reactions.- Kenso Soai and Tsuneomi Kawasaki: Asymmetric autocatalysis of pyrimidyl alkanol.- Douglas C. Behenna and Brian M. Stoltz: Natural Products as Inspiration for Reaction Development: Catalytic Enantioselective Decarboxylative Reactions of Prochiral Enolate Equivalents. Hisashi Yamamoto: Acid Catalysis in Organic Synthesis.
The ASI workshop on "Selectivities in Lewis Acid Promoted Reactions" held in the Emmantina-Hotel in Athens-Glyfada, Greece, October 2-7, 1988 was held to bring some light into the darkness of Lewis acid induced processes. As such the workshop reflects some current trends in organic synthesis, where Lewis acids are becoming a powerful tool in many different modern reactions, e.g. Diels-Alder reactions, Ene reactions, Sakurai reactions, and in general silicon and tin chemistry. The objective of this meeting was to bring together most of the world experts in the field to discuss the major reactions promoted by Lewis acids. Organic synthesis will play a major role in this book connected with some fundamental mechanistic work on allylsilane and -tin chemistry. Both natural product synthesis and unnatural molecules are presented in the chapters. The book presents all the 15 invited lectures and the contributions of 15 posters. I am confident that the material presented in this book will stimulate the chemistry, which has been discussed on our meeting, around the world. The meeting and the book were only possible through a grant of the NATO Scientific Affairs Devision and financial support by the following companies: Kali Chemie (Hannover, W-Germany), E. Merck (Darmstadt, W-Germany), Sandoz (Basel, Switzerland), Schering (Berlin, W-Germany).
Comprehensive Coordination Chemistry II (CCC II) is the sequel to what has become a classic in the field, Comprehensive Coordination Chemistry, published in 1987. CCC II builds on the first and surveys new developments authoritatively in over 200 newly comissioned chapters, with an emphasis on current trends in biology, materials science and other areas of contemporary scientific interest.