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Study on reactive intermediates and solvent participation by means of interplay of photochemical and thermochemical reactions

通过光化学和热化学反应的相互作用研究反应中间体和溶剂参与

基本信息

批准号：
14340202
负责人：
OKUYAMA Tadashi
金额：
$ 10.88万
依托单位：
University of Hyogo (2004)Himeji Institute of Technology (2002-2003)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

Solvolysis of optically active 4-methylcyclohexylidenemethyl iodonium salt gives a rearranged cycloheptenyl product with complete retention of optical purity, indicating that primary vinyl cation is not formed. This was also the case even in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), and ionic liquids as well as in a solution of high ionic strength. However, the photosolvolysis leads to racemization of the products via formation of the primary vinylic cation. The same iodonium salt leads to racemized substitution products in the presence of a base in HFIP. The racemization takes place via elimination-addition mechanism with the cycloheptyne intermediate. Thermal reaction of styryl iodonium salt occurs via beta-phenyl participation with a benzenium ion intermediate. Photoreaction of the styryl substrate also takes place via the primary vinyl cation without participation. Observation of intermediate benzenium ion via photo-generated primary vinyl cation was attempted by laser photolysis in a nanosecond time scale, but there found no indication of formation of this bridged cation.Photo-induced cycloaddition of naphthalene derivatives carrying a chiral side chain with o-chloranil took place stereoslectively.. Laser photolysis of this solution at 355 nm showed formation of a cation radical of the naphthalene substrate. The same cation radical was thermally generated with ferric salt in HFIP solution, and circular dichroic spectra were observed showing the Cotton effects around the wavelength of absorption. This result suggests that there is some interaction between the naphthalene ring and the chiral side chain, which is considered to be responsible for the stereoselectivity of the cycloaddition. Similar naphthalene derivatives carrying a chiral carboxylate side chain were subjected to the reaction with singlet oxygen, which led to synthesis of optically active hydroperoxides.

旋光性4-甲基环己基甲基碘盐溶液溶解得到重排的环庚基产物，光学纯度完全保留，表明未形成伯乙烯基阳离子。即使在1,1,1,3,3,3-六氟-2-丙醇（HFIP）和离子液体以及高离子强度的溶液中也是如此。然而，光溶解通过形成初级乙烯基阳离子导致产物的外消旋化。在HFIP中，相同的碘盐在碱的存在下导致外消旋取代产物。外消旋作用是通过环庚烷中间体的消加成机制进行的。苯基碘盐的热反应是通过苯基与苯离子中间体的参与而发生的。苯乙烯基底物的光反应也通过初级乙烯基阳离子进行，而不参与。用激光光解法在纳秒时间尺度上观察了中间苯离子通过光生成的伯乙烯基阳离子，但没有发现这种桥接阳离子形成的迹象。带手性侧链的萘衍生物与邻氯胺进行了立体定向的光诱导环加成反应。激光在355nm处光解该溶液，发现形成了一个阳离子基的萘底物。在HFIP溶液中用铁盐热生成相同的阳离子自由基，在吸收波长附近观察到圆二向色光谱显示棉花效应。这一结果表明萘环与手性侧链之间存在一定的相互作用，这被认为是造成环加成的立体选择性的原因。携带手性羧酸侧链的萘衍生物与单线态氧反应，合成了具有光学活性的氢过氧化物。