IJOC  Vol.3 No.3 , September 2013
Evaluation of TlOH Effect for Pd0-Mediated Cross-Coupling of Methyl Iodide and Excess Boronic Acid Ester toward Fabrication of [11C]CH3-Incorporated PET Tracer
ABSTRACT
The use of thallium(I) hydroxide (TlOH) as a base is known to extremely accelerate the Suzuki-Miyaura cross-coupling reaction using organoboronic acid or organoboronic acid ester as a substrate. Here, we investigated the effects of TlOH by comparing with other conventional bases such as KOH, K2CO3, and CsF for Pd0-mediated rapid cross-coupling reactions between CH3I and organoborane reagents, such as phenyl-, (Z)-4-benzyloxy-2-butenyl-, and benzylboronic acid pinacol esters under the conditions CH3I/borane/Pd0/base (1:40:1:3) in THF/H2O or DMF/H2O for 5 min with an aim to fabricate a PET tracer efficiently. Consequently, however, the use of TlOH was much less efficient than the other bases for the acceleration of cross-coupling reactions. Thus, it was reconfirmed that the milder and non-toxic conditions using K2CO3 or CsF so far developed by our group were most appropriate for the rapid C-methylations.

Cite this paper
H. Koyama, H. Doi and M. Suzuki, "Evaluation of TlOH Effect for Pd0-Mediated Cross-Coupling of Methyl Iodide and Excess Boronic Acid Ester toward Fabrication of [11C]CH3-Incorporated PET Tracer," International Journal of Organic Chemistry, Vol. 3 No. 3, 2013, pp. 220-223. doi: 10.4236/ijoc.2013.33030.
References
[1]   N. Miyaura and A. Suzuki, “Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds,” Chemical Reviews, Vol. 95, No. 7, 1995, pp. 2457-2483.

[2]   N. Miyaura, K. Yamada and A. Suzuki, “A New Stereospecific Cross-Coupling by the Palladium-Catalyzed Reaction of 1-Alkenylboranes with 1-Alkenyl or 1-Alkynyl Halides,” Tetrahedron Letters, Vol. 20, No. 36, 1979, pp. 3437-3440.

[3]   J. Uenishi, J.-M. Beau, R. W. Armstrong and Y. Kishi, “Dramatic Rate Enhancement of Suzuki Diene Synthesis. Its Application to Palytoxin Synthesis,” Journal of the American Chemical Society, Vol. 109, No. 15, 1987, 109, pp. 4756-4758. The magnitude of acceleration is roughly estimated to be the following order: KOH (relative rate = 1), TlOEt (5), Ag2O (30), and TlOH (1000). TlOH conditions are effective in water. For the review, see: S. R. Chemler, D. Trauner and S. J. Danishefsky, “The B-Alkyl Suzuki-Miyaura Cross-Coupling Reaction: Development, Mechanistic Study, and Applications in Natural Product Synthesis,” Angewandte Chemie International Edition, Vol. 40, No. 24, 2001, pp. 4544-4568.

[4]   M. J. Welch and C. S. Redvanly, “Handbook of Radiopharmaceuticals Radiochemistry and Applications”, Wiley, England, 2003.

[5]   M. Suzuki, H. Koyama, M. Takashima-Hirano and H. Doi, “Pd0-Mediated Rapid C-[11C]Methylation and C-[18F] Fluoromethylation: Revolutionary Advanced Methods for General Incorporation of Short-Lived Positron-Emitting 11C and 18F Radionuclides in an Organic Framework,” In: C.-H. Hsieh, Ed., Positron Emission Tomography—Current Clinical and Research Aspects, InTech, Open Access publisher, 2012, pp. 115-152.

[6]   M. Suzuki, H. Doi, M. Bjorkman, Y. Andersson, B. Langstrom, Y. Watanabe and R. Noyori, “Rapid Coupling of Methyl Iodide with Aryltributylstannanes Mediated by Palladium(0) Complexes: A General Protocol for the Synthesis of 11CH3-Labeled PET Tracers,” Chemistry—A European Journal, Vol. 3, No. 12, 1997, pp. 2039-2042.

[7]   H. Doi, I. Ban, A. Nonoyama, K. Sumi, C. Kuang, T. Hosoya, H. Tsukada and M. Suzuki, “Palladium(0)-Mediated Rapid Methylation and Fluoromethylation on Carbon Frameworks by Reacting Methyl and Fluoromethyl Iodide with Aryl and Alkenyl Boronic Acid Esters: Useful for the Synthesis of [11C]CH3–C-and [18F]FCH2-C-Containig PET Tracers (PET = Positron Emission Tomography),” Chemistry—A European Journal, Vol. 15, No. 16, 2009, pp. 4165-4171.

[8]   H. Koyama, Z. Zhang, R. Ijuin, Siqin, J. Son, Y. Hatta, M. Ohta, M. Wakao, T. Hosoya, H. Doi and M. Suzuki, “Pd0-Mediated Rapid Coupling of Methyl Iodide with Excess Amounts of Benzyl and Cinnamylboronic Acid Estsers: Efficient Method for Incorporation of Positron-Emitting 11C Radionuclide into Organic Frameworks by Coupling between Two sp3-Hybridized Carbons,” RSC Advances, Vol. 3, 2013, pp. 9391-9401.

[9]   E. D. Hostetler, G. E. Terry and H. D. Burns, “An Improved Synthesis of Substituted [11C]Toluenes via Suzuki Coupling with [11C]Methyl Iodide,” Journal of Labelled Compounds and Radiopharmaceuticals, Vol. 48, No. 9, 2005, pp. 629-634.

[10]   W. Yuan and S. Ma, “CuCl–K2CO3-Catalyzed Highly Se-lective Borylcupration of Internal Alkynes—Ligand Effect,” Organic & Biomolecular Chemistry, Vol. 10, No. 36, 2012, pp. 7266-7268.

[11]   A. A. C. Braga, N. H. Morgon, G. Ujaque and F. Maseras, “Computational Characterization of the Role of the Base in the Suzuki-Miyaura Cross-Coupling Reaction,” Journal of the American Chemical Society, Vol. 127, No. 25, 2005, pp. 9298-9307.

[12]   M. Suzuki, H. Doi, T. Hosoya, B. Langstrom and Y. Watanabe, “Rapid Methylation on Carbon Frameworks Leading to the Synthesis of a PET Tracer Capable of Imaging a Novel CNS-Type Prostacyclin Receptor in Living Human Brain,” Trends in Analytical Chemistry, Vol. 23, No. 8, 2004, pp. 595-607.

[13]   T. Takashima, S. Kitamura, Y. Wada, M. Tanaka, Y. Shigihara, H. Ishii, R. Ijuin, S. Shiomi, T. Nakae, Y. Watanabe, Y. Cui, H. Doi, M. Suzuki, K. Maeda, H. Kusuhara, Y. Sugiyama and Y. Watanabe, “PET Imaging-Based Evaluation of Hepatobiliary Transport in Human with (15R)-11C-TIC-Me,” The Journal of Nuclear Medicine, Vol. 53, No. 5, 2012, pp. 741-748.

 
 
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