Catalysis of Organic..

Musolino, Apa, Donato and Pietropaolo 24728. Hydrogenation and IsomerizationReactions of Olefinic Alcohols Catalyzed inHomogeneous Phase by Rh(I) ComplexesMaria G. Musolino, Giuseppe Apa, Andrea Donato and Rosario PietropaoloAbstractDepartment of Mechanics and Materials, Faculty of Engineering, University ofReggio Calabria, Loc. Feo di Vito, I-89060 Reggio Calabria, Italypietropaolo@ing.unirc.itHomogeneous hydrogenation and isomerization reactions of α,β-unsaturatedalcohols have been investigated in ethanol by using tris(triphenylphosphine)chlororhodium(I), RhCl(PPh 3 ) 3 , and triethylamine at 303 K and 0.1 MPa hydrogenpressure. The results can be interpreted on the basis of a proposed mechanism inwhich RhH(PPh 3 ) 3 is the active species. A comparison is also reported withanalogous reactions carried out in the absence of NEt 3 .IntroductionIn a previous paper we have investigated homogeneous hydrogenation andisomerization reactions of (Z)-2-butene-1,4-diol in ethanol at 303 K by using theWilkinson catalyst (RhCl(PPh 3 ) 3 ) in the presence of triethylamine. AlthoughRhCl(PPh 3 ) 3 was, so far, largely used for hydrogenation reactions and mainly affordsfully hydrogenated compounds, it is worth noting that such a catalyst, in the presenceof triethylamine and (Z)-2-butene-1,4-diol, is more selective towards the geometricisomerization product, (E)-2-butene-1,4-diol (1).In this work we extend our study to the hydrogenation and isomerization of aseries of α,β-unsaturated alcohols, such as 2-propen-1-ol (A2), (E)-2-buten-1-ol(EB2), (Z)-2-penten-1-ol (ZP2), (E)-2-penten-1-ol (EP2), (Z)–2-hexen-1-ol (ZH2),(E)–2-hexen-1-ol (EH2), carried out in the presence of RhCl(PPh 3 ) 3 , with andwithout triethylamine (NEt 3 ), at 303 K, using ethanol as solvent. The major targets ofour research are to investigate the influence of the unsaturated alcohol structure onthe product distribution and to verify the possibility of extending the results,previously obtained with (Z)-2-butene-1,4-diol, to other analogous substrates.ResultsReactions of α,β-unsaturated alcohols with hydrogen were carried out in the presenceof RhCl(PPh 3 ) 3 , with and without NEt 3 , at 303 K, 0.1 MPa hydrogen pressure andusing ethanol as solvent. Under the experimental conditions adopted, the reaction, in