| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 1998: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1997: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
Radical-based reductive reactions as well as oxidation reactions play important roles in organic synthesis. especially for polyfunctionalized molecules like biologically active compounds. Although many synthetic reactions involving free radicals as intermediates have employed tributyltin hydride as reducing agent, the replacement of such toxic and relatively expensive organotin compounds has been performed with other hydrogen donors containing the Si-H bond. Alkyl- and/or aryl-substituted silane seem to be good alternatives to the stannanes, butthese reagents require relatively drastic reaction conditions due to their lower hydrogen-donating abilities. Recently, tris (trimethylsilyl) silane has been reported to be an effective and versatile reducing agent, of which the Si-H bond is believed to be dramatically weakened by a hyperconjugation between a generated silyl radical and adjacenttrimethylsilyl group. However, the compound is relatively expensive and, in addition, is unstable under aerobic conditions. More recently, we have alsc reported that 9,1O-dihydro-9, 1O-disilaanthracene is an effective reducing agent under such the conditions. The reactivity of the compound is attributed to a transannular (p-d) it-interaction between the silyl radical and d-orbital of silicon atoniat the opposite site. In this study, we would like to investigate a stabilization factor of such the silyl radical and develope new reducing agents.
As the results, we can describe as follows :
i) The anthracene derivative is the most reactive agent among the compounds prepared in our laboratory to date.
ii) Under the photochemical reacrion conditions, we investigated the configurational isomerization reaction of the silyl radical. The driving force of the reaction is believed to be a transannular (p-d) it-interaction between the generatec silyl radical and a d-orbital of silicon atom at the opposite site, because a 9-silaanthracene derivative was not isomerizec under the same conditions.
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