A one-pot three-step reaction, isomerization/hydroformylation/hydrogenation of internal alkenes to n-alcohols, was accomplished by employing a Rh/Ru dual-catalyst system. By using a combination of Rh(acac)(CO)2/bisphosphite and Shvo's catalyst, (Z)-2-tridecene was converted to 1-tetradecanol in 83% yield with high normal/iso selectivity (n/i = 12). The method was applicable to other internal alkenes, including functionalized alkenes, such as an alkenol and an alkenoate. Furthermore, addition of a third component, Ru3(CO)12, effectively improved the n/i ratio in the tandem isomerization/hydroformylation/hydrogenation of methyl oleate (from n/i = 1.9 to 4.4). Control experiments revealed that the isomerization was mediated by both Rh and Ru and that the coexistence of Rh and Ru was essential for hydrogenation of aldehyde under H2/CO.
A practical method for the asymmetric transfer hydrogenation of a-substituted ketones was developed utilizing oxo-tethered N-sulfonyldiamine-ruthenium complexes. Reduction by HCO 2 H and HCO 2 K in a mixed solvent of EtOAc/H 2 O allowed for the selective synthesis of halohydrins from 2-bromoacetophenone (98%) and 2-chloroacetophenone (> 99%), leading to suppressed undesired side reactions stemming from formylation under the typical reaction conditions using an azeotropic 5:2 mixture of HCO 2 H and Et 3 N. A range of functional groups, such as halogens, methoxy, nitro, dimethylamino, and ester groups, were well tolerated, highlighting the potential of this method. Nearly complete selectivity with a preferable ee was maintained even with a substrate/ catalyst (S/C) ratio of 5000. This catalyst system was also effective for the asymmetric reduction of a-sulfonated ketones without eroding the leaving group.
Tandem Isomerization/Hydroformylation/Hydrogenation of Internal Alkenes to n-Alcohols Using Rh/Ru Dual-or Ternary-Catalyst Systems. -A one-pot three--step reaction, isomerization/hydroformylation/hydrogenation of internal alkenes to n-alcohols, is accomplished by employing a Rh/Ru dual-catalyst system. The method is applicable to a series of internal alkenes, including functionalized, such as alkenol (X) and alkenoate (XII). Furthermore, addition of ruthenium carbonyl as a third catalyst component effectively improves the transformation of methyl oleate. Control experiments reveal that the isomerization is mediated by both Rh and Ru and that the coexistence of Rh and Ru is essential for the aldehyde hydrogenation under H 2/CO. -(YUKI, Y.; TAKAHASHI, K.; TANAKA, Y.; NOZAKI*, K.; J. Am. Chem. Soc. 135 (2013) 46, 17393-17400, http://dx.doi.org/10.1021/ja407523j ; Dep. Chem.
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