Alkene cis-Dihydroxylation by [(Me3tacn)(CF3CO2)RuVIO2]ClO4 (Me3tacn = 1,4,7-Trimethyl-1,4,7-triazacyclononane): Str
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- 作者：Wing-Ping Yip ; Wing-Yiu Yu ; Nianyong Zhu ; and Chi-Ming Che
- 刊名：Journal of the American Chemical Society
- 出版年：2005
- 出版时间：October 19, 2005
- 年：2005
- 卷：127
- 期：41
- 页码：14239 - 14249
- 全文大小：209K
- 年卷期：v.127,no.41(October 19, 2005)
- ISSN：1520-5126
文摘
cis-Dioxoruthenium(VI) complex [(Me3tacn)(CF3CO2)RuVIO2]ClO4 (1, Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) reacted with alkenes in aqueous tert-butyl alcohol to afford cis-1,2-diols in excellentyields under ambient conditions. When the reactions of 1 with alkenes were conducted in acetonitrile,oxidative C=C cleavage reaction prevailed giving carbonyl products in >90% yields without any cis-diolformation. The alkene cis-dihydroxylation and C=C cleavage reactions proceed via the formation of a [3+ 2] cycloadduct between 1 and alkenes, analogous to the related reactions with alkynes [Che et al. J.Am. Chem. Soc. 2000, 122, 11380]. With cyclooctene and trans-
-methylstyrene as substrates, the Ru(III)cycloadducts 28230a10001">[(Me3tacn)(CF3CO2)R2823000000">uIIIO(H)CH(CH2)6HC O]ClO4 (4a) and 28230a10002">[(Me3tacn)(CF3CO2)R2823000000">uIIIO(H)PhCHCH(CH3) O]ClO4 (4b) were isolated and structurally characterized by X-ray crystal analyses. Thekinetics of the reactions of 1 with a series of p-substituted styrenes has been studied in acetonitrile bystopped-flow spectrophotometry. The second-order rate constants varied by 14-fold despite an overall spanof 1.3 V for the one-electron oxidation potentials of alkenes. Secondary kinetic isotope effect (KIE) wasobserved for the oxidation of -d2-styrene (kH/kD = 0.83 ± 0.04) and 
-deuteriostyrene (kH/kD = 0.96 ±0.03), which, together with the stereoselectivity of cis-alkene oxidation by 1, is in favor of a concertedmechanism.
-methylstyrene as substrates, the Ru(III)cycloadducts -d2-styrene (kH/kD = 0.83 ± 0.04) and -deuteriostyrene (kH/kD = 0.96 ±0.03), which, together with the stereoselectivity of cis-alkene oxidation by 1, is in favor of a concertedmechanism.