Barton-McCombie Reaction

Definition:

Deoxygenation of alcohols via their xanthate ester which undergo free radical scission upon treatment with tri-n-butyltin hydride:

Frequency of appearance:

        This bar graph represents all of the online articles that were found to contain this specific name reaction in the title of the article. Tetrahedron letters, Tetrahedron, Synthetic letters, Synthesis, Journal of Organic Chemistry and Journal of the American Chemical Society are represented here. This table by no means represents the periodicity of the name reaction found in the literature.

Original References:

1. Barton, D.H.R.; McCombie, S.W. J. Chem. Soc., Perkin Trans. I, 1574-1585 (1975).

Recent academic references: Click here for more references

            2.    Asymmetric synthesis of (-)-Adaline

• Itoh, T.; Yamazaki, N.; Kibayashi, C.; Org. Lett.; 2002 (In Press)

            3.   Deoxygenative functionalization of hydroxy groups via xanthates with tetraphenyldisilane

• Togo, H.; Matsubayashi, S.; Yamazaki, O.; Yokoyama, M.; J. Org. Chem.;; 65(9); 2816-2819 ( 2000).

            4.    Diastereofacial Selective Addition of Ethynylcerium Reagent and Barton-McCombie Reaction as the Key Steps for the                     Synthesis of C-3'-Ethynylribonucleosides and of C-3'-Ethynyl-2'-deoxyribonucleosides

• Jung, P. M. J.; Burger, A.; Biellmann, J.-F.; J. Org. Chem.; 62(24); 8309-8314 (1997).  

            5.    Bu₃SnH-Catalyzed Barton-McCombie Deoxygenation of Alcohols

• Lopez, R.M.; Hays, D.S.; Fu, G.C.* J. Am. Chem. Soc., 119, 6949-6950 (1997).

            6.    http://chem-faculty.ucsd.edu/theodorakis/ET36.pdf

            7.    http://www.tciamerica.com/news/newslib/96spr_a.htm

Recent process references:

Mechanism: http://www.arkat.org/arkat/journal/Named Reactions/Barton-McCombie.htm

Scope and limitations:

• Reducing agents: diphenylsilane and tributylstannane
• R on the xanthate: H, CH₃, SCH₃, Ph, Oph, imidazolyl
• Reactivity of alcohol: 1⁰ >> 2⁰ > 3⁰
• Sn copound limitations: toxic, cost and difficult to remove from reaction.
• IPA xanthate cleavage possible (Schonberg reaction by-products thiocarbonates).
• Polar solvents are usually employed.
• Si and P compounds are used as proton donors but not as efficient.
• Azobisisobutyronitrile (AIBN) sometimes used as an initiator (Me₂CCN× ) which attack the tributylstannane to give the thiophilic tributylstannyl radical species. ¹

Synonyms:

Barton Deoxygenation.