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Org. Synth. 2011, 88, 207-211
DOI: 10.15227/orgsyn.088.0207
Discussion Addendum for: PALLADIUM(0)-CATALYZED REACTION OF 9-ALKYL-9-BORABICYCLO[3.3.1]NONANE WITH 1-BROMO-1-PHENYLTHIOETHENE: 4-(3-CYCLOHEXENYL)-2-PHENYLTHIO-1-BUTENE
Submitted by Norio Miyaura
Original Article: Org. Synth. 1993, 71, 89
Discussion
The cross-coupling reactions of organoboron compounds have proved to be a general method for a wide range of selective carbon-carbon bond forming reactions.1 In 1989, the cross-coupling reaction of 9-alkyl-9-BBN with 1-alkenyl and aryl halides or triflates was found to proceed smoothly in the presence of PdCl2(dppf) and K3PO4•nH2O.2 This coupling reaction of B-alkyl compounds has been reviewed.3 , 4 The reaction is limited to primary alkylboranes; hydroboration of terminal alkenes with 9-BBN is the most convenient way to furnish the desired boron reagents.The reaction is catalyzed by PdCl2(dppf),2 PdCl2(dppf)/2Ph3As,5 or other palladium-phosphine complexes in the presence of a base (Table 1).Since the presence of water greatly accelerates the reaction, the use of the hydrate of inorganic bases such as K3PO4•nH2O (entry 1) or aqueous bases (entries 2 and 4) is generally recommended.5 On the other hand, solid sodium methoxide added to 9-alkyl-9-BBN dissolves in THF by forming the corresponding ate-complex, which enables room temperature coupling under non-aqueous conditions (entries 3 and 5).2 Treatment of 9-methoxy-9-BBN with primary-alkyllithiums is an alternative for in situ preparation of analogous boron ate-complexes.6 The presence of KBr (1 equiv) is often critical to prevent decomposition of the catalyst for reactions of aryl and 1-alkenyl triflates (entry 6).7
Sp3-sp3 bond formation between two alkyl derivatives has been much less successful among the possible combinations of different-type nucleophiles and electrophiles.Difficulties arise from the oxidative addition of haloalkanes (RCH2CH2X) to a palladium(0) complex due to accompanying formation of RCH=CH2 and RCH2CH3 and from the susceptibility of alkylpalladium(II) intermediates to β-hydride elimination.8 In spite of these difficulties, sp3-sp3 bond formation occurs smoothly between primary-alkyl halides and primary-alkylboron compounds where each reactant possesses β-hydrogen (entries 8 and 9).9 The coupling with secondary alkyl halides has been limited to cyclopropyl iodides.10 , 11
The reactions of the corresponding alkylboronic acids and [alkylBF3]K12 are significantly slower than that of trialkylboranes, but methylboroxine (MeBO)3 or methylboronic acid alkylates bromoarenes with a common palladium/triphenylphosphine catalyst (entry 10).13 Analogous reactions of alkylboronic acids possessing β-hydrogen are achieved by the use of Qphos (2) for aryl or 1-alkenyl bromides, triflates and chlorides (entry 11),14 a dppf complex for iodides, bromides and triflates,12 , 15 and N-cyclic carbene (1)16 for arene diazonium salts.These reactions are limited to use for primary-alkylboronic acids; however, cyclopropylboronic acid derivatives alkylate aryl and 1-alkenyl halides or triflates17 and acyl chlorides18 without loss of stereochemistry of the cyclopropane ring (eq 1).
Table 1. Reaction Conditions for Coupling of primary-Alkylboron Derivatives



				Table 1. Reaction Conditions for Coupling of primary-Alkylboron Derivatives
The connection of two fragments via the hydroboration-cross coupling sequence has found a wide range of applications in the synthesis of natural products and functional molecules,1 , 3 , 4 including bacterial metabolites epothilone A and B,22 ciguatoxin,23 clinically useful 2-alkylcarbapenems,24 and a novel class of glycomimetic compounds, aza-C-disaccharides.25

References and Notes
  1. Reviews, (a) Metal-Catalyzed Cross-Coupling Reactions - Second, Completely Revised and Enlarged Edition, A.de Meijere, F.Diederich, Eds.; Wiley-VCH (2004); pp 41-123.(b) Suzuki, A.; Brown, H.C.Organic Syntheses Via Boranes Vol.3: Suzuki Coupling, Aldrich (2003).(c) Topics in Current Chemistry Vol.219, Miyaura, N.Ed.; Springer-Verlag (2002); pp 11-59.(d) Metal-Catalyzed Cross-Coupling Reactions, Diederich, F.; Stang, P.J.Eds.; Wiley-VCH (1998); 49-97.(e) Miyaura, N.; Suzuki, A. Chem.Rev.1995, 95, 2457.
  2. Miyaura, N.; Ishiyama, T.; Sasaki, H.; Ishikawa, M.; Satoh, M.; Suzuki, A.J.Am.Chem.Soc. 1989, 111, 314.This report describes the use of K3PO4; however, the chemical company purchased this reagent later changed the label to its hydrate, K3PO4•nH2O whereby n is 2 to 3.
  3. Chemler, S.R.; Trauner, D.; Danishefsky, S.J. Angew .Chem.Int.Ed. 2001, 40, 4545.
  4. Netherton, M.W.; Fu, G.C.Adv.Synth.Catal.2004, 346, 1525.
  5. Johnson, C.R.; Braun, M.P.J.Am.Chem.Soc.1993, 115, 11014.
  6. Marshall, J.A.; Johns, B.A.J.Org.Chem. 1998, 63, 7885.
  7. Oh-e, T.; Miyaura, N.; Suzuki, A.J.Org.Chem.1993, 58, 2201.
  8. (a) Ishiyama, T.; Abe, S.; Miyaura, N.; Suzuki, A.Chem Lett.1992, 691.(b) Echavarren, A.M.Angew.Chem.Int.Ed.2005, 44, 3962.
  9. (a) Netherton, M.R.; Dai, C.; Neuschütz, K.; Fu, G.C.J.Am.Chem.Soc.2001, 123, 10099.(b) Kirchhoff, J.H.; Dai, C.; Fu, G.C. Angew.Chem.Int.Ed. 2002, 41, 1945.
  10. Charette, A.B.; Giroux, A.; J.Org.Chem.1996, 61, 8718.
  11. Charette, A.B.; Freitas-Gil, R.P.D.Tetrahedron Lett. 1997, 38, 2809.
  12. G.A.Molander, T.Ito, Org.Lett.2001, 3, 393.
  13. Gray, M.; Andrews, I.P.; Hook, D.F.; Kitteringham, J.; Voyle, M.; Tetrahedron Lett.2000, 41, 6237.
  14. Kataoka, N.; Shelby, Q.; Stambuli, J.P.; Hartwig, J.F. J.Org.Chem.2002, 67, 5553.
  15. (a) Zou, G.; K.Reddy, Y.K.; Falck, J.R.Tetrahedron Lett.2001, 42, 7213.(b) Occhiato, E.G.; Trabocchi, A.; Guarna, A.J.Org.Chem.2001, 66, 2459.
  16. Andrus, M.B.; Song, C. Org.Lett.2001, 3, 3761.
  17. (a) Yao, M.L.; Deng, M.-Z.J.Org.Chem.2000, 65, 5034.(b) Zhou, S.-M.; Deng, M.-Z.; Xia, L.-J.; Tang, M.-H.Angew.Chem.Int.Ed.Engl.1998, 37, 2845.
  18. Chen, H.; Deng, M.-Z.Org Lett.2000, 2, 1649.
  19. Fürstner, A.; Leitner, A. Synlett 2001, 290.
  20. Sasaki, M.; Fuwa, H.; Inoue, M.; Tachibana, K.Tetrahedron Lett. 1998, 39, 9027.
  21. Sasaki, M.; Fuwa, H.; Ishikawa, M.; Tachibana, K.Org Lett.1999, 1, 1075.
  22. Balog, A.; Meng, D.; Kamenecka, T.; Bertinato, P.; Su, D-S.; Sorensen, E.J.; S.J.Danishefsky, S.J.Angew.Chem.Int.Ed.1996, 35, 2801.
  23. (a) H.Takakura, H.; K.Noguchi, K.; M.Sasaki, M.; K.Tachibana, K. Angew.Chem.Int.Ed. 2001, 40, 1090.(b) Sasaki, M.; Ishikawa, M.; Fuwa, H.; Tachibana, K. Tetrahedron.2002, 58, 1889.
  24. Narukawa, Y.; Nishi, K.; Onoue, H.Tetrahedron. 1997, 53, 539.
  25. Johns, B.A.; Pan, Y.T.; Elbein, A.D.; Johnson, C.R.J.Am.Chem.Soc.1997, 119, 4856.
  26. Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
Norio Miyaura was born in Hokkaido in Japan in 1946.He received his B.Eng.and Dr.Eng.from Hokkaido University.He became a Research Associate and an Associate Professor in the A.Suzuki research group, and then was promoted to the rank of Professor in the same group in 1994.He is now emeritus and a specially appointed Professor after his retirement from Hokkaido University in 2010.In 1981, he joined the J.K.Kochi group at Indiana University as a postdoctoral fellow to study the epoxidation of alkenes catalyzed by metal-salen complexes.His current interests are mainly in the field of metal-catalyzed reactions of organoboron compounds, with emphasis of applications to organic synthesis such as catalyzed hydroboration, palladium-catalyzed cross-coupling reactions of organoboronic acids, rhodium- or palladium-catalyzed conjugate addition reactions of arylboronic acids, and addition and coupling reactions of diborons and pinacolborane for the synthesis of organoboronic esters.