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Catalytic Deoxygenation of 1,2‐Propanediol to Give n ‐Propanol
Author(s) -
Schlaf Marcel,
Ghosh Prasenjit,
Fagan Paul J.,
Hauptman Elisabeth,
Bullock R. Morris
Publication year - 2009
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200800685
Subject(s) - deoxygenation , chemistry , aldehyde , ruthenium , hydride , medicinal chemistry , catalysis , trifluoromethanesulfonate , diol , protonation , photochemistry , organic chemistry , hydrogen , ion
Deoxygenation of 1,2‐propanediol (1.0 M in sulfolane) catalyzed by bis(dicarbonyl)(μ‐hydrido)(pentamethylcyclopentadiene)ruthenium trifluoromethanesulfonate ({[Cp*Ru(CO) 2 ] 2 (μ‐H)} + OTf − ) (0.5 mol%) at 110 °C under hydrogen (750 psi) in the presence of trifluoromethanesulfonic acid (HOTf) (60 mM) gives n ‐propanol as the major product, indicating high selectivity for deoxygenation of the internal hydroxy group over the terminal hydroxy group of the diol. The deoxygenation of 1,2‐propanediol is strongly influenced by the concentration of acid, giving faster rates and proceeding to higher conversions as the concentration of HOTf is increased. Propionaldehyde was observed as an intermediate, being formed through acid‐catalyzed dehydration of 1,2‐propanediol. This aldehyde is hydrogenated to n ‐propanol through an ionic pathway involving protonation of the aldehyde, followed by hydride transfer from the neutral hydride, dicarbonyl(pentamethylcyclopentadiene)ruthenium hydride [Cp*Ru(CO) 2 H]. The proposed mechanism for the deoxygenation/hydrogenation reaction involves formation of a highly acidic dihydrogen complex [Cp*Ru(CO) 2 (η 2 ‐H 2 )] + OTf − .