Hydroacylation

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Hydroacylation is a type of organic reaction in which an aldehyde is added over an alkene or alkyne bond. The reaction product is a ketone. The reaction requires a metal catalyst and intramolecular reaction is favored over an intermolecular one. With alkynes the reaction product is an cyclopentenone.[1]

Hydroacylation General

The reaction was discovered by K. Sakai in 1972 as part in a synthetic route to certain prostanoids.[2] The reagent in this reaction was tin tetrachloride. With an stoichiometric amount of Wilkinson's catalyst in chloroform, acetonitrile or benzene an equal amount of a cyclopropane was formed as the result of decarbonylation.

Hydroacylation Sakai 1972

The first catalytic application was reported by Miller in 1976 [3] in the reaction of 4-pentenal with Wilkinson's catalyst to form cyclopentanone. In this reaction the solvent was saturated with ethylene.

Cyclopentanone Synthesis Miller

Cyclopentane ring-formation is favored, the reaction product of 5-pentenal is again a cyclopentanone. Another suitable catalyst is cationic rhodium compound Rh(dppe)ClO4

Reaction mechanism[edit]

In a general reaction mechanism step one in hydroacylation is oxidative addition of the metal into the aldehyde carbon-hydrogen bond followed by side-on addition of the alkene, then followed by reductive elimination. A lurking side-reaction is decarbonylation from the acyl metal hydride RCH2(CO)MH to the alkane RCH3 and M(CO) via the RCH2M(CO)H intermediate.

Hydroacylation reaction Mechanism

Asymmetric hydroacylation[edit]

Hydroacylation as an asymmetric reaction was first demonstrated by James and Young in 1983 (kinetic resolution) [4][5] and by Sakai in 1989 (true asymmetric synthesis) [6][7] both employing rhodium and a chiral diphosphine ligand. In one application the ligand is Me-DuPhos:[8]

Asymmetric hydroAcylation Marce 2008

References[edit]

  1. ^ Transition Metal Catalyzed Alkene and Alkyne Hydroacylation Michael C. Willis Chem. Rev. 2009 doi:10.1021/cr900096x
  2. ^ Synthetic studies on prostanoids 1 synthesis of methyl 9-oxoprostanoate K. Sakai, J. Ide, O. Oda and N. Nakamura Tetrahedron Letters Volume 13, Issue 13, 1972, Pages 1287-1290 doi:10.1016/S0040-4039(01)84569-X
  3. ^ Transition-metal-promoted aldehyde-alkene addition reactions Charles F. Lochow, Roy G. Miller J. Am. Chem. Soc., 1976, 98 (5), pp 1281–1283 doi:10.1021/ja00421a050
  4. ^ The asymmetric cyclisation of substituted pent-4-enals by a chiral rhodium phosphine catalyst Brian R. James and Charles G. Young J. Chem. Soc., Chem. Commun., 1983, 1215 - 1216, doi:10.1039/C39830001215
  5. ^ Catalytic decarbonylation, hydroacylation, and resolution of racemic pent-4-enals using chiral bis(di-tertiary-phosphine) complexes of rhodium(I) Brian R. James, and Charles G. Young Journal of Organometallic Chemistry Volume 285, Issues 1-3, 16 April 1985, Pages 321-332 doi:10.1016/0022-328X(85)87377-0
  6. ^ Asymmetric cyclization reactions by Rh(I) with chiral ligands Yukari Tauraa, Masakazu Tanakaa, Kazuhisa Funakoshia and Kiyoshi Sakai Tetrahedron Letters Volume 30, Issue 46, 1989, Pages 6349-6352 doi:10.1016/S0040-4039(01)93891-2
  7. ^ Asymmetric cyclization reactions. Cyclization of substituted 4-pentenals into cyclopentanone derivatives by rhodium(I) with chiral ligands Yukari Taura, Masakazu Tanaka, Xiao-Ming Wu, Kazuhisa Funakoshi and Kiyoshi Sakai Tetrahedron Volume 47, Issue 27, 1991, Pages 4879-4888 doi:10.1016/S0040-4020(01)80954-6
  8. ^ Synthesis of D- and L-Carbocyclic Nucleosides via Rhodium-Catalyzed Asymmetric Hydroacylation as the Key Step Patricia Marce, Yolanda Dıaz, M. Isabel Matheu, and Sergio Castillon Org. Lett., 2008, 10 (21), pp 4735–4738 doi:10.1021/ol801791g