Cycloaddition Reactions of Active Cyclic Frustrated Lewis Pairs

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We have recently developed syntheses of first examples of active frustrated five- and six-membered cyclic phosphane/borane Lewis pairs (P/B FLPs) and shown that they undergo a number of cycloaddition reactions with organic π-reagents. The rules, which govern such FLP cycloadditions and their often subsequently observed Alder-Rickert analogous cycloreversions, shall be clarified by this project in order to provide a sound basis to develop the specific chemistry of these cycloaddition/cycloreversion sequences. This will include the typical chemistry of the zwitterionic hetero-norbornenes and -bicyclo[2.2.2]octanes as well as the synthesis of optically active cyclic FLPs, obtained by alkene exchange reactions, and their utilization as active metal-free catalysts for asymmetric hydrogenation. We have planned applications of cyclic FLPs in synthetic cycles in phospha-Stork chemistry. Unsaturated dimers of our new cyclic five- and six-membered cyclic FLPs will be used for topochemical ring closure reactions, which for the first time might open viable entries to FLP crown and FLP cage compounds. Both are probably of interest for small molecule activation.