| Research Abstract |
1. A pentacoordinate 3-methoxycarbony1-1,2-oxaphosphetane bearing the Martin ligand has been synthesized as the first example for 1,2-oxaphosphetane with an electron-withdrawing group such as carbonyl group at the 3-position. A novel type of spirophosphorane containing two 1,2-oxaphosphetane rings has also been synthesized successfully. 2. Pentacoordinate 1,2-oxasiletanides, intermediates of the Peterson reaction, have been obtained by deprotonation of the corresponding beta-hydroxy silanes, which were prepared by sequential treatment of the vinylsilane bearing the Martin ligand with t-BuLi and then with carbonyl compounds, with KH in the presence of 18-crown-6. Similarly, a pentacoordinate 1,2-oxastannetanide and 1,2-oxagermetanide have been synthesized, although stabilzation by the Martin ligand is not necessary in the former case.X-ray crystallographic analyzes of these compounds indicate that these compounds have a distorted trigonal bipyramidal structures with two or one (in the case of the oxastannetanide) oxygen atom (s) at the apical position (s) . 3. Tetracoordinate 1,2-oxatthietane and 1,2-oxaselenetane were synthesized by oxidative cyclization of the corresponding bis (hydroxy) chalcogenides with bromine in the presence of Et_3N.It was also indicated by X-ray crystallography that they have pseudo-trigonal bipyramidal structures. 4.Thermolyses of the group 14 and 15 element compounds gave quantitatively the corresponding olefins via a slightly polar transition state. However, themolyses of group 16 element compounds afforded no Wittig reaction products, but migration products induced by the heterolysis of the chalcogen-oxygen bond. It is very interesting to point out that a trace of Corey-Chaykovski reaction product, oxirane, was obtained in the case of thermolysis of 1,2-oxathietane. These results have been published as short communications.
|
