The first part of this thesis discussed our study of a highly disastereoselective asymmetric thio-Claisen rearrangement with a C2 symmetric chiral auxiliary. Most of the asymmetric thio-Claisen rearrangements investig...
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The first part of this thesis discussed our study of a highly disastereoselective asymmetric thio-Claisen rearrangement with a C2 symmetric chiral auxiliary. Most of the asymmetric thio-Claisen rearrangements investigated to date suffer from low diastereofacial selectivity as a consequence of free rotation around the C-N bond in the N,S-ketene acetal intermediate. After careful analysis of the examples from literature, we designed a system incorporating a C2 symmetric amine as the chiral auxiliary. During this study, we discovered a unique aspect associated with a C 2-symmetric chiral auxiliary in this system. The rearrangements with allylic units possessing a substituent cis to the allylic sulfide take place with exceptionally high diastereoselectivity, among the highest reported for any Claisen rearrangement. The chiral auxiliary can be removed under the reductive-hydrolysis conditions. A simple, predictive model based on a chair-like transition state is provided to explain the extraordinary asymmetric inductions observed. The second part of the thesis described our efforts and achievements on the total synthesis of strychnos alkaloids. Since the synthesis of strychnine previously reported by this group involved a low-yielding step, the conversion of isostrychnine to strychnine, the original goal for the present study was to synthesize strychnine via the Wieland-Gumlich aldehyde, known to be a superior precursor to strychnine. Based on the general strategy involving intramolecular Diels-Alder reaction and heck cyclization as the key steps, a sequence leading to the Wieland-Gumlich aldehyde was designed. Through this study, we achieved the first total syntheses of dehydrodesacetylretuline, desacetylretuline and zenkerene. In addition, by exploiting the acylation chemistry of imine azaenolates, we achieved the syntheses of akuammicine and norfluorocurarine. In a similar way, 18-hydroxyakuammicine and 18-hydroxynorfluorocurarine were synthesized. The former is a know
Molybdenum and tungsten components in catalysts Bu4N〔Mo（CO）5Cl〕-EtAlCl2andWCl6-Bu4Sn were immobilized respectively on *** influence of immobilization ofthe soluble catalysts on their catalytic behavior in the meta...
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Molybdenum and tungsten components in catalysts Bu4N〔Mo（CO）5Cl〕-EtAlCl2andWCl6-Bu4Sn were immobilized respectively on *** influence of immobilization ofthe soluble catalysts on their catalytic behavior in the metathesis of 1—hexene was *** has been found that polystyrene is a good supporting material among all thepolymers *** immobilized catalysts have higher stability and better selectivity incomparison with their homogeneous *** metathesis yield of 1-hexene is in-creased by fourfold with WCl6immobilized on *** reason for the increase ofstability of the immobilized catalyst is discussed.
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