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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 10, Number 4
BKCSDE 10(4)
April 20, 1989 

Alkylhydridorhodium(Ⅲ) Route for Isomerization and Hydrogenation of Unsaturated Alcohols with Rh(ClO4)(CO)(PPh3)2 and [Rh(CO)(PPh3)3]ClO4 under Hydrogen
Chong Shik Chin*, Jeonghan Park, Choongil Kim
Catalytic isomerization of unsaturated alcohols to the corresponding carbonyl compounds with Rh(ClO)4(CO)(PPh3)2 (1) and [Rh(CO)(PPh3)3]ClO4 (2) is faster under hydrogen (where hydrogenation also occurs to give saturated alcohols) than under nitrogen. The isomerization under hydrogen seems to occur through an alkylhydridorhodium(Ⅲ) complex which also undergoes reductive elimination to give hydrogenation products, saturated alcohols. The isomerization under hydrogen is faster with 2 than with 1, which is understood by acceleration of the last step, enol formation by PPh3 dissociated from 2 and present in the reaction mixture when 2 is used as catalyst. Relative rates of the isomerization observed for different unsaturated alcohols are interpreted by steric effects of substituted groups and numbers of hydrogens to be abstracted by the rhodium of the intermediate, alkylhydridorhodium(Ⅲ) to undergo the reductive elimination to give enol which is then rapidly converted into a carbonyl compound. It has been observed that the hydrogenation is relatively significant when reactions occur slowly whereas the isomerization is predominant when reactions proceed rapidly.
360 - 362
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