FULL PAPER Hydration of Propargylic Alcohols by Ruthenium Catalysts, with Dominant Anti-Markovnikov Regioselectivity, Formation of α,β-Unsaturated Products and Catalytic Decarbonylation to 1-Alkenes Nicola d’Alessandro, [a] Milena Di Deo, [a] Monica Bonetti, [a] Lucia Tonucci, [a] Antonino Morvillo, [b] and Mario Bressan* [a] Keywords: Ruthenium / Alkynes / Phthalocyanines / Hydration / Decarbonylation Ruthenium catalysts — water-soluble ruthenium sulfo- phthalocyanine and heterogeneous ruthenium hydroxy- apatite complexes — proved to be effective for the hydration of propargylic alcohols in entirely aqueous media. 1-Phenyl- 2-propyn-1-ol underwent an unprecedented catalytic hydra- tion-decarbonylation-dehydration reaction, giving rise to styrene and carbon monoxide; 2-propyn-1-ol and 3-butyn-2- ol gave predominantly the products of anti-Markovnikov ad- Introduction Alkynes are useful intermediates for the synthesis of car- bonyl compounds through the well-known metal-catalyzed hydration reaction. Typically, the addition reactions of water to 1-alkynes are catalyzed by a variety of transition metal salts and complexes, [1-7] including RuCl 3 , [8,9] all of which follow Markovnikov’s rule to give ketones. Only very recently [10] has it been reported that the reaction can be regioselectively oriented to the formation of aldehydes (anti-Markovnikov addition) in the presence of catalytic amounts of some ruthenium() organometallic derivatives, containing either cyclopentadienyl [11,12] or indenyl [13] moiet- ies, although temperatures of around 100 °C were still re- quired. The accepted mechanism involves the rearrange- ment of the π-adduct deriving from the conventional inter- action with the terminal alkynes at the metal center into a metal-vinylidene intermediate [13] or, alternatively, a hydrido- alkynyl complex, [12] the latter of which has recently been isolated as an intermediate in the activation of propargylic alcohols by [Cp*RuCl(dppe)]; [14] both the proposed inter- mediates are prone to nucleophilic attack by water at the α- carbon atom. Previous results [15] showed the critical role played by the π-alkyne/vinylidene equilibrium in the re- [a] Universita ` ‘‘G. d’Annunzio’’ di Chieti-Pescara, Dipartimento di Scienze, Viale Pindaro 42, 65127, Pescara, Italy E-mail: bressan@sci.unich.it [b] Universita ` di Padova, Dipartimento di Chimica Inorganica and Centro C.N.R., Via Marzolo 1, 35100 Padova, Italy 810  2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/ejic.200300562 Eur. J. Inorg. Chem. 2004, 810-817 dition, together with products of hydration-dehydration (α,β- rearrangement) and, to a minor extent, the decarbonylation products, ethene or propene, respectively. Hydrations were also conducted in D 2 O, giving indications of the mechanism of the reactions and apparently ruling out the allenylidene route for the α,β-rearrangement. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) gioselectivity of the hydration reactions, suggesting that ad- dition of water to the π-adduct might follow Markovnikov’s rule, eventually yielding methylketones, whereas addition to the vinylidene intermediate would lead to an acyl complex and, finally, aldehydes. However, only a few examples have reported good selectivity in the aldehyde formation, [11,13] as several alternative reaction pathways, not strictly dealing with conventional hydration, could become dominant. Among them, the catalytic cleavage of the carbon-carbon triple bond is particularly attractive, since it could represent an interesting topic from the synthetic point of view, if high selectivities can be attained in mild experimental conditions. So far, however, alkyne cleavage has also been demonstrated to work effectively in only a few cases. [16,17] The potential for the use of both ruthenium catalysts and water as reagent prompted our interest in the subject. In the present work we tested the water-soluble ruthenium() complex ruthenium sulfophthalocyanine (RuPcS), pre- viously studied by us as an effective catalyst for a variety of organic substrates in aqueous media, [18-22] and the hetero- geneous ruthenium hydroxyapatite (RuHAP) catalyst, suc- cessfully tested for the aerobic oxidation of alcohols to alde- hydes, reportedly via a metal-hydrido species, [23] which pro- ved to work satisfactorily also in aqueous media. [24] This paper deals with the catalytic hydration of a number of pro- pargylic (2-propyn-1-ol, 3-butyn-2-ol, 1-phenyl-2-propyn-1- ol and 1,1-diphenyl-2-propyn-1-ol) and non-propargylic al- cohols (3-butyn-1-ol and 4-pentyn-1-ol). A variety of reac- tion pathways were observed, depending upon the nature of the substrate and the catalyst; among them, cleavage of