Design of the Molecules Bearing Specific Stereochemistry and Its Application to the Development of New Reactions

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We are extensively developing a new system in which stereochemistry and reaction of the unique molecule can be regulated under the electronic control.Conformational analysis of various six-membered ring compounds possessing alkoxy and silyloxy substituents has been performed by utilizing their dynamic <@D11@>D1H- and <@D113@>D1C-NMR, <@D1119@>D1Sn-NMR, and X-ray analyses. Thus, it was clarified that chair-type 3-silyloxy-substituted glutaric anhydride and glutarimide and the chair-type cyclohexanones possessing alkoxy or silyloxy group at the C4 position can predominantly adopt each corresponding substituent-axial conformer in their solution. Similar axial or pseudoaxial preference of silyloxy and benzyloxy groups at C4 of chair-type thiane-1-oxides, thiane-1, 1-dioxides, and dihydrothiines was recognized on their dynamic <@D11@>D1H-NMR spectra. Such axial preference of alkoxy and silyloxy groups of several six-membered compounds was also observed in their crystallographic structures. Existence of the electron-withdrawing moiety ((]SY.di-substituted left.[)C=O, (]SY.di-substituted left.[)SO, (]SY.di-substituted left.[)SO<@D22@>D2) and the low basicity of silyloxy- and alkoxy-oxygen atom proved to be essential for adopting the axial conformer, which could be rationalized in terms of a general hypothesis ; stabilization of the axial conformer due to C3, 5-Hsigma, C4-Osigma<@D1*@>D1 orbital overlap.Several molecules, adopting a bent conformation stacked with both aromatics such as triazoles and benzene derivatives, have been developed and characterized by X-ray crystallographic and ^1H-NMR analyses. Bridging both aromatic moieties with a sulfonic ester bond seems to be an essential factor for the bent conformation. Design and synthesis of new molecules adopting a unique sigmoid conformation have been achieved on the basis of a molecular mechanic calculation.