Kulinkovich reaction

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The Kulinkovich reaction describes the organic synthesis of substituted cyclopropanols through reaction of esters with dialkyl­dialkoxy­titanium reagents, which are generated in situ from Grignard reagents containing a hydrogen in beta-position and titanium(IV) alkoxides such as titanium isopropoxide.^[1] This reaction was first reported by Oleg Kulinkovich and coworkers in 1989.^[2]

Titanium catalysts are ClTi(OiPr)₃ or Ti(OiPr)₄, ClTi(OtBu)₃ or Ti(OtBu)₄, Grignard reagents are EtMgX, PrMgX or BuMgX. Solvents can be Et₂O, THF, toluene. Tolerated

The step leading to the titanacyclopropane has been scrutinized computationally. Although the dialkyldiisopropoxytitanium complex has been proposed to undergo β hydrogen elimination followed by C–H reductive elimination to give the alkane and 1, it was found that β hydrogen abstraction by the alkyl group, leading directly to products without the intermediate titanium hydride, is a more favorable process.[3]

In broad strokes, and in a formal retrosynthetic sense, titanacyclopropane 1 behaves like a 1,2-dianion which adds into the ester twice: after the first addition into the ester, the resultant tetrahedral intermediate 2 collapses to give β-titanio ketone 3, which undergoes a second intramolecular addition to give the titanium salt of the cyclopropanol (4). (This species then undergoes transmetalation with Grignard reagent to regenerate 1 and close the catalytic cycle and give the product in the form of the magnesium salt (5).)

The reaction mechanism has been the subject of theoretical analysis.^[4] Certain points remain nevertheless obscure. Intermediate titanium complexes of the ate type have been proposed by Kulinkovich.^[5]

Ligand exchange with olefins

In 1993, the team of Kulinkovich highlighted the aptitude of the titanacyclopropanes to undergo

The methodology has been extended to intramolecular reactions^[8]

De Meijere variation

With

The intramolecular reaction is also known:^{[11][12][13][14][15][16][17][18][19][20]}

Szymoniak variation

In the Szymoniak variation the substrate is a nitrile and the reaction product a cyclopropane with a primary amine group.^[21][22]

The reaction mechanism is akin the Kulinkovich reaction:

Additional reading

• Kulinkovich, O. G.; Sviridov, S. V.; Vasilevski, D. A. (1991). "Titanium(IV) Isopropoxide-Catalyzed Formation of 1-Substituted Cyclopropanols in the Reaction of Ethylmagnesium Bromide with Methyl Alkanecarboxylates". Synthesis. 1991 (3): 234.
  doi:10.1055/s-1991-26431
  .
• Kulinkovich, O. G.; De Meijere, A. (2000). "1,n-Dicarbanionic Titanium Intermediates from Monocarbanionic Organometallics and Their Application in Organic Synthesis". Chem. Rev. 100 (8): 2789–834.
  PMID 11749306
  .
• Sato, F.; Urabe, H.; Okamoto, S. (2000). "Synthesis of organotitanium complexes from alkenes and alkynes and their synthetic applications". Chem. Rev. 100 (8): 2835–86.
  PMID 11749307
  .
• Wu, Y.-D.; Yu, Z.-X. (2001). "A theoretical study on the mechanism and diastereoselectivity of the Kulinkovich hydroxycyclopropanation reaction". J. Am. Chem. Soc. 123 (24): 5777–86.
  PMID 11403612
  .
• Kulinkovich, O. G. (2004). "Alkylation of carboxylic acid derivatives with dialkoxytitanacyclopropane reagents". Russ. Chem. Bull. 53 (5): 1065–1086.
  S2CID 98642553
  .
• Wolan, A.; Six, Y. (2010). "Synthetic transformations mediated by the combination of titanium(IV) alkoxides and grignard reagents: Selectivity issues and recent applications. Part 1: Reactions of carbonyl derivatives and nitriles". Tetrahedron. 66: 15–61.
  doi:10.1016/j.tet.2009.10.050
  .
• Wolan, A.; Six, Y. (2010). "Synthetic transformations mediated by the combination of titanium(IV) alkoxides and Grignard reagents: Selectivity issues and recent applications. Part 2: Reactions of alkenes, allenes and alkynes". Tetrahedron. 66 (17): 3097–3133.
  doi:10.1016/j.tet.2010.01.079
  .
• Corey, E. J.; Rao, S. A.; Noe, M. C. (1994). "Catalytic Diastereoselective Synthesis of Cis-1,2-Disubstituted Cyclopropanols from Esters Using a Vicinal Dicarbanion Equivalent". Journal of the American Chemical Society. 116 (20): 9345.
  doi:10.1021/ja00099a068
  .