Palladium and Raney Nickel Catalyzed Methanolic Cleavage of Stable Borane-Amine Complexes
Michel Couturier,* John L. Tucker, Brian M. Andresen, Pascal Dubé and Joanna T. Negri
*Process Research and Development, Pfizer Global Research and Development,
Eastern Point Road, P.O. Box 8013, Groton, Connecticut 06340-8013, Email:
michel_a_couturier
groton.pfizer.com
M. Couturier, J. L. Tucker, B. M. Andresen, P. Dube, J. T. Negri, Org. Lett., 2001, 3, 465-467.
DOI: 10.1021/ol006969+
Abstract
Palladium and Raney nickel catalyze the methanolysis of strongly complexed borane-amine adducts. The method is applicable to primary, secondary, tertiary, and aromatic amines, and the mildness of the reaction conditions allows preservation of otherwise labile functional groups.
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Details
The study explores the use of palladium and Raney nickel as catalysts for the methanolysis of borane-amine adducts, enabling the liberation of strongly complexed amines under mild conditions. This method is effective for primary, secondary, tertiary, and aromatic amines, preserving labile functional groups. Borane-amine adducts, common in synthetic organic chemistry and industrial processes, are typically stable and require harsh conditions for cleavage. The research demonstrates that treatment with 10% palladium on carbon or Raney nickel in methanol significantly accelerates the decomplexation process. For instance, the palladium-catalyzed reaction of a borane-benzylamine adduct yielded debenzylated pyrrolidine in 97% yield within 12 hours, compared to over 170 hours without the catalyst. The method is simple, practical, and compatible with acid-sensitive protective groups. Raney nickel offers a slower, more controlled reaction rate, making it suitable for various amine-boranes. The study also highlights the influence of steric bulk and basicity on decomplexation rates, with methanol being the preferred protic source due to its volatility. This catalytic methanolysis method is expected to be widely applicable in academic and industrial settings, providing a neutral, rapid, and operationally simple approach to cleaving borane-amine complexes.
Key Words
Methanolysis, Borane-Amine Adducts, Borane, Deoxygenations
ID: J54-Y2001-420
