Ruthenium(II) Complex Catalyzed O-Borylation of Alcohols with Vinylboronates

Abstract

A new, highly effective method for the selective synthesis of boryl ethers via O-borylation of alcohols with vinylboronates catalyzed by the Ru-H complexes [Ru(CO)ClH(PPh₃)₃] and [Ru(CO)ClH(PCy₃)₂] is described. The mechanism of catalysis of this new de-ethenative borylation is supported by equimolar reaction of Ru-B complex with alcohol.

Key words

homogeneous catalysis - vinylboronates - ruthenium - coupling reactions - boryl ethers

References and Notes

• For recent reviews, see:
• 1a Marciniec B. Acc. Chem. Res.  2007,  40:  943 
• 1b Marciniec B. Coord. Chem. Rev.  2005,  249:  2374 
• 2a Marciniec B. Jankowska M. Pietraszuk C. Chem. Commun.  2005,  663 
• 2b Jankowska M. Pietraszuk C. Marciniec B. Zaidlewicz M. Synlett  2006,  1695 
• 3a Marciniec B. Ławicka H. Majchrzak M. Kubicki M. Kownacki I. Chem. Eur. J.  2006,  12:  244 
• 3b Marciniec B. Ławicka H. Appl. Organomet. Chem.  2008,  22:  510 
• 4a Marciniec B. Dudziec B. Kownacki I. Angew. Chem. Int. Ed.  2006,  45:  8180 
• 4b Marciniec B. Ławicka H. Dudziec B. Organometallics  2007,  26:  5188 
• 4c Marciniec B. Ławicka H. Dudziec B. J. Organomet. Chem.  2008,  693:  235 
• 4d Dudziec B. Marciniec B. Organometallics  2008,  27:  5598 
• 5 Kakiuchi F. Matsumoto M. Sonoda M. Fukuyama T. Chatani N. Murai S. Furukawa N. Seki Y. Chem. Lett.  2000,  750 
• 6a Park J.-W. Chang H.-J. Jun Ch.-H. Synlett  2006,  771 
• 6b Park J.-W. Jun Ch.-H. Org. Lett.  2007,  9:  4073 
• 7 Marciniec B. Pawluć P. Hreczycho G. Macina A. Madalska M. Tetrahedron Lett.  2008,  49:  1310 
• 8 Marciniec B. Walkowiak J. Chem. Commun.  2008,  2695 
• 9a Bell NJ. Cox AJ. Cameron NR. Evans JSO. Marder TB. Duin MA. Elsevier CJ. Baucherel X. Tulloch AAD. Tooze RP. Chem. Commun.  2004,  1854 
• 9b Hoffmann RW. Schafer F. Haeberlin E. Rhode T. Korber K. Synthesis  2000,  2060 
• 9c Greene TW. Wuts PGM. Protective Groups in Organic Synthesis   John Wiley & Sons, Inc.; New York: 1999.  p.196 
• 10a Baron O. Knochel P. Angew. Chem. Int. Ed.  2005,  44:  3133 
• 10b Billingsley KL. Buchwald SL. Angew. Chem. Int. Ed.  2008,  47:  4695 
• 10c Chan KL. Watkins SE. Mak ChSK. McKiernan MJ. Towns CR. Pascua SI. Holmes AB. Chem. Commun.  2005,  5766 
• 10d Dudek SP. Pouderoijen M. Abbel R. Schenning APHJ. Meijer EW. J. Am. Chem. Soc.  2005,  127:  11763 
• 11 Oki A. Adams L. Luo Z. Inorg. Chem. Commun.  2008,  11:  275 
• 12 Malkowsky IM. Fröhlich R. Griesbach U. Pütter H. Waldvogel SR. Eur. J. Inorg. Chem.  2006,  1690 
• 13a Alaviuhkola T. Bobacka J. Nissinen M. Rissanen K. Ivaska A. Pursiainen J. Chem. Eur. J.  2005,  11:  2071 
• 13b Pineschi M. Bertolini F. Crotti P. Macchia F. Org. Lett.  2006,  8:  2627 
• 15 Clark GR. Irvine GJ. Roper WR. Wright LJ. Organometallics  1997,  16:  5499 
• 17a Ferrnando-Miguel G. Wu P. Huffman JC. Caulton KG. New. J. Chem.  2005,  29:  193 
• 17b Jazzar RFR. Bhatia PH. Mahon MF. Whittlesey MK. Organometallics  2003,  22:  670 
• 17c Churchill MR. Keil KM. Bright FV. Pandey S. Baker GA. Keister JB. Inorg. Chem.  2000,  39:  5807 
• 17d Burling S. Kociok-Kohn G. Mahon MF. Whittlesey MK. Williams JMJ. Organometallics  2005,  24:  5868 

14

O-Borylation of alcohols by vinylboronates; general procedure: The ruthenium catalyst [Ru(CO)ClH(PPh₃)₃] (II) (2 mol%) was dissolved in toluene and placed in a glass ampoule. The reagents and dodecane as internal standard (5% by volume all components), alcohol (0.5 mmol) and
2-vinyl-1,3,2-dioxaborinane (1-2.5 mmol) were added and the ampoule was heated at 60-80 ˚C for 24 h. Alcohol conversion was determined by GC and GC-MS. After the reaction, the solvent and excess borane were removed under vacuum, and the crude product was purified by column chromatography (silica gel modified with HMDS; hexane-EtOAc).
2-Butoxy-1,3-dioxaborinane: ^¹H NMR (300 MHz, CDCl₃): δ = 1.10 (t, J = 7.2 Hz, 3H, CH ₃), 1.78 (q, J = 7.0 Hz, 2H, CH ₂CH₃), 1.92 (quin, J = 5.5 Hz, 2H, BOCH₂CH ₂CH₂O), 2.16 (brH ₂CH₂CH₃), 3.85 [t, J = 4.6 Hz, 2H, CH ₂ (CH₂)₂CH₃], 4.03 (t, J = 5.5 Hz, 4H, BOCH ₂CH₂CH ₂O). ^¹³C NMR (75 MHz, CDCl₃): δ = 15.8 (CH₃), 20.3 (CH₂CH₃), 27.2 (BOCH₂ CH₂CH₂O), 33.2 (CH₂CH₂CH₃), 62.7 (BOCH₂CH₂ CH₂O), 64.7 [BOCH_{2 (}CH₂)₂CH₃]. ^¹¹B NMR (96 MHz, CDCl₃): δ = 28.7. MS (EI): m/z (%) = 143 (1)
[M⁺ - 15], 129 (2), 115 (100), 103 (29), 85 (22), 71 (11), 56 (14). Anal. Calcd for C₇H₁₅BO₃: C, 53.21; H, 9.57. Found: C, 53.01; H, 9.44.
3-(1′,3′,2′-Dioxaborinan-2′-yloxy)propanonitrile: ^¹H NMR (300 MHz, CDCl₃): δ = 1.99 (quin, J = 5.5 Hz, 2H, BOCH₂CH ₂CH₂O), 2.60 (t, J = 6.0 Hz, 2H, CH ₂C≡N), 3.89 (t, J = 6.0 Hz, 2H, CH ₂CH₂C≡N), 4.03 (t, J = 5.5 Hz, 4H, BOCH ₂CH₂CH ₂O). ^¹³C NMR (75 MHz, CDCl₃): δ =
26.3 (CH₂C≡N), 27.1 (BOCH₂ CH₂CH₂O), 57.9 (BOCH₂CH₂C≡N), 62.8 (BOCH₂CH₂ CH₂O), 117.6 (C≡N). ^¹¹B NMR (96 MHz, CDCl₃): δ = 28.7. MS (EI): m/z (%) = 156 (6) [M⁺ + 1], 140 (7), 125 (10), 115 (100), 98 (25), 85 (23), 71 (10), 54 (28). Anal. Calcd for C₆H₁₀BNO₃: C, 58.74; H, 9.31; N, 9.04. Found: C, 58.88; H, 9.23; N, 9.18.

16

Experimental procedure for the stoichiometric experiment: In an NMR tube, [Ru(BO₂C₆H₄)(CO)Cl(PCy₃)₂] (III) (10 mg, 0.012 mmol) and cyclohexan-1-ol (1.6 mg, 0.016 mmol) and toluene-d ₈ (0.6 mL) were placed under argon. The reaction was carried out at 80 ˚C and monitored by ^¹H NMR.