標題: | A remarkable effect of C-O-C bond angle strain on the regioselective double nucleophilic substitution of the acetal group of tetraacetal tetraoxa-cages and a novel hydride rearrangement of tetraoxa-cages |
作者: | Wu, HJ Chern, JH 交大名義發表 應用化學系 National Chiao Tung University Department of Applied Chemistry |
公開日期: | 16-五月-1997 |
摘要: | A remarkable effect of C-O-C bond angle strain on the regioselective double nucleophilic substitution of the acetal group of tetraacetal tetraoxa-cages and a novel regioselective and stereoselective hydride rearrangement of tetraoxa-cages are reported. Reaction of the tetraacetal tetraoxa-cages 1 with 3 equiv of triethylsilane (at -78 degrees C), cyanotrimethylsilane (at 25 degrees C), and allyltrimethylsilane (at -78 degrees C) in dichloromethane in the presence of TiCl4 gave the double nucleophilic substitution products 2, 6, and 7 in 85-90% yields, respectively. No detectable amount of other regioisomers was obtained. Reaction of 1a with (methylthio)trimethylsilane and (phenylthio)trimethylsilane in dichloromethane in the presence of TiCl4 at -78 degrees C gave the symmetric products 10a,b and the unsymmetric products 11a,b in ratios of 8-10:1. The stereochemistry of the symmetric substitution products was proven by X-ray analysis of the crystalline compound 10a. The mechanism of the double nucleophilic substitution of the tetraoxa-cages 1 are discussed. Treatment of the tetraoxa-cages 1a,c and 22a-c with 2 equiv of TiCl4 or MeSO3H in dichloromethane at 25 degrees C for 3 h regioselectively and stereoselectively gave the novel hydride rearrangement products 16a,b and 23a-c respectively. No detectable amount of other regioisomers was observed. The stereochemistry of the hydride rearrangement was proven by DIBAL-H reduction of 16 and 23 and X-ray analysis of the reduction product 24a. We attribute the high regioselectivity of the double nucleophilic substitution and the hydride rearrangement of the tetraoxa-cages 1 to the bond angle strain of the unusually large bond angle of C(3)-O(4)-C(5) of the tetraoxa-cages. |
URI: | http://hdl.handle.net/11536/533 |
ISSN: | 0022-3263 |
期刊: | JOURNAL OF ORGANIC CHEMISTRY |
Volume: | 62 |
Issue: | 10 |
起始頁: | 3208 |
結束頁: | 3214 |
顯示於類別: | 期刊論文 |