Electric Literature of 301224-40-8. Chemistry is an experimental science, and the best way to enjoy it and learn about it is performing experiments.Introducing a new discovery about 301224-40-8, Name is (1,3-Dimesitylimidazolidin-2-ylidene)(2-isopropoxybenzylidene)ruthenium(VI) chloride
Conversion of essential-oil allylbenzenes (phenylpropenoids) to high-value fine chemicals via isomerization-metathesis is reported. The target reaction sequence involves isomerization of ArCH2CH=CH21 into the corresponding conjugated olefins 2, and ensuing cross-metathesis with acrylates to generate ArCH=CHCO2R 3. The second-generation Hoveyda catalyst HII was chosen for the metathesis step. A range of lead candidates was assessed for the isomerization step, of which most active was the Grotjahn catalyst [CpRu(PN)(MeCN)]PF6([4]PF6; PN = 2-PiPr2-4-tBu-1-Me-imidazole). The following order of isomerization activity was determined, using the isomerization of estragole 1a to anethole 2a (Ar = p-MeOC6H4) as a probe reaction: [CpRu(PN)(MeCN)]PF6> RuHCl(CO)(PPh3)3> Ru(Me-allyl)2(COD) > Pd2Br2(PtBu3)2> RuHCl(PPh3)3> RuCl3(mu2-C)(mu2,kappa1-C,eta6-Mes-H2IMes)Ru(H)(H2IMes) (the “Grubbs hydride”) > RuHCl(CO)(H2IMes)(PCy3) > RuHCl(CO)(IMes)(PCy3) > RuHCl(CO)(PCy3)2. To maximize process efficiency, a systematic comparison of orthogonal tandem catalysis versus sequential catalyst addition was undertaken, using catalysts [4]PF6and HII. The impact of each process type on product selectivity and catalyst compatibility was assessed. Selectivity was undermined in tandem isomerization-metathesis by competing metathesis of 1. Sequential catalyst addition eliminated this problem. The isomerization catalyst [4]PF6adversely affected metathesis yields when equimolar with HII, an effect traced to the imidazole functionality in [4]PF6. However, at the low catalyst loadings required for efficient isomerization (0.1 mol% [4]PF6), negligible impact on metathesis yields was evident. The target cinnamates and ferrulates were obtained in quantitative yields by coupling these steps in a one-pot isomerization-metathesis protocol.
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Highly efficient and robust molecular ruthenium catalysts for water oxidation,
Catalysts | Special Issue : Ruthenium Catalysts – MDPI