Synlett 2013; 24(10): 1260-1262
DOI: 10.1055/s-0033-1338847
cluster
© Georg Thieme Verlag Stuttgart · New York

Substituent Effects in NHC–Boranes: Reactivity Switch in the Nucleophilic Fluorination of NHC–Boranes

Malika Makhlouf Brahmi
a   UPMC Université Paris 06, IPCM (UMR 7201), 4 Pl. Jussieu, C. 229, 75005 Paris, France
,
Max Malacria
a   UPMC Université Paris 06, IPCM (UMR 7201), 4 Pl. Jussieu, C. 229, 75005 Paris, France
,
Dennis P. Curran
b   Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA
,
Louis Fensterbank
a   UPMC Université Paris 06, IPCM (UMR 7201), 4 Pl. Jussieu, C. 229, 75005 Paris, France
,
Emmanuel Lacôte*
a   UPMC Université Paris 06, IPCM (UMR 7201), 4 Pl. Jussieu, C. 229, 75005 Paris, France
c   Université de Lyon, Institut de chimie de Lyon, UMR 5265 CNRS-Université Lyon I-ESCPE Lyon, 43 Bd du 11 novembre 1918, 69616 Villeurbanne, France   Fax: +33(4)72431795   Email: emmanuel.lacote@univ-lyon1.fr
› Author Affiliations
Further Information

Publication History

Received: 23 April 2013

Accepted after revision: 03 May 2013

Publication Date:
28 May 2013 (online)


Abstract

Substituents on the boron atom of NHC–boranes direct the reactivity of the ligated boreniums obtained through hydride abstraction. Depending on the electronics of the substituent, the reaction is selectively steered toward either B-substitution or Lewis base exchange.

Supporting Information

 
  • References and Notes


    • For reviews, see:
    • 1a De Vries TS, Prokofjevs A, Vedejs E. Chem. Rev. 2012; 112: 4642
    • 1b Piers WE, Bourke SC, Conroy KD. Angew. Chem. Int. Ed. 2005; 44: 5016

    • For recent references, see:
    • 1c Tsurumaki E, Hayashi S.-Y, Tham FS, Reed CA, Osuka A. J. Am. Chem. Soc. 2011; 133: 11956
    • 1d Someya CI, Inoue S, Praesang C, Irran E, Driess M. Chem. Commun. 2011; 47: 6599
    • 1e Prokofjevs A, Vedejs E. J. Am. Chem. Soc. 2011; 133: 20056
    • 1f Mansaray HB, Rowe AD. L, Phillips N, Niemeyer J, Kelly M, Addy DA, Bates JI, Aldridge S. Chem. Commun. 2011; 47: 12295
    • 1g Ines B, Patil M, Carreras J, Goddard R, Thiel W, Alcarazo M. Angew. Chem. Int. Ed. 2011; 50: 8400
    • 1h Del GA, Singleton PJ, Muryn CA, Ingleson MJ. Angew. Chem. Int. Ed. 2011; 50: 2102
    • 1i Del GA, Helm MD, Solomon SA, Caras-Quintero D, Ingleson MJ. Chem. Commun. 2011; 47: 12459
    • 1j De Vries TS, Prokofjevs A, Harvey JN, Vedejs E. J. Am. Chem. Soc. 2009; 131: 14679
    • 2a Matsumoto T, Gabbaï FP. Organometallics 2009; 28: 4252
    • 2b Tsai J.-H, Lin S.-T, Yang RB.-G, Yap GP. A, Ong T.-G. Organometallics 2010; 29: 4004
    • 2c McArthur D, Butts CP, Lindsay DM. Chem. Commun. 2011; 47: 6650
    • 2d Solovyev A, Geib SJ, Lacôte E, Curran DP. Organometallics 2012; 31: 54

    • For a review on NHC-borane chemistry, see:
    • 2e Curran DP, Solovyev A, Makhlouf Brahmi M, Fensterbank L, Malacria M, Lacôte E. Angew. Chem. Int. Ed. 2011; 50: 10294
  • 3 Solovyev A, Chu Q, Geib SJ, Fensterbank L, Malacria M, Lacôte E, Curran DP. J. Am. Chem. Soc. 2010; 132: 15072
    • 4a Eisenberger P, Bailey AM, Crudden CM. J. Am. Chem. Soc. 2012; 134: 17384
    • 4b Farrell JM, Hatnean JA, Stephan DW. J. Am. Chem. Soc. 2012; 134: 15728
    • 4c Chen J, Lalancette RA, Jäkle F. Chem. Commun. 2013; 49: 4893
  • 5 Walton JC, Makhlouf Brahmi M, Monot J, Fensterbank L, Malacria M, Curran DP, Lacôte E. J. Am. Chem. Soc. 2011; 133: 10312
    • 6a Hudnall TW, Gabbaï FP. J. Am. Chem. Soc. 2007; 129: 11978
    • 6b Chiu C.-W, Gabbaï FP. Organometallics 2008; 27: 1657
    • 7a De Vries TS, Vedejs E. Organometallics 2007; 26: 3079
    • 7b Funke M.-A, Mayr H. Chem. Eur. J. 1997; 3: 1214
  • 8 General Procedure To a solution of NHC–borane complex (1 equiv) in CH2Cl2 (0.07 M) was added the triphenylcarbenium derivative (1 equiv), then phenol (1 equiv). The reaction mixture was stirred at r.t. for 5 min. The solvent was then evaporated in vacuo, and the residue was purified by flash chromatography. Typical Characterization Data for Compound 2a Mp 222–227 °C. IR (diamond): ν = 2960, 2930, 2870, 2360 (B–F), 1460, 1260, 1060, 1015, 930, 800, 760, 735 cm–1. 1H NMR (400 MHz, CDCl3): δ = 7.50 (t, J = 7.8 Hz, 2 H, p-H of IPr), 7.28 (d, J = 7.8 Hz, 4 H, m-H of IPr), 7.04 (s, 2 H, NCH), 6.94 (t, J = 6.9 Hz, 1 H, p-H of Ph), 6.88 (t, J = 6.8 Hz, 2 H, m-H of Ph), 6.77 (d, J = 6.6 Hz, 2 H, o-H of Ph), 2.61–2.55 [m, 4 H, CH(CH3)2], 1.20 [d, J = 6.8 Hz, 12 H, CH(CH 3)2], 1.13 [d, J = 6.8 Hz, 12 H, CH(CH 3)2]. 13C NMR (100 MHz, CDCl3): δ = 145.5 (C arom.), 134.2 (C arom.), 131.7 (CH arom.), 130.4 (CH arom.), 126.6 (CH arom.), 125.9 (CH arom.), 123.8 (NCH), 123.8 (CH arom.), 29.0 [CH(CH3)2], 25.9 (CHCH 3CH3), 22.3 (CHCH3CH 3). 11B NMR (133 MHz, BF3·OEt2): δ = 4.8 (br s). 19F NMR (376 MHz, CFCl3): δ = –153.2 (br s). HRMS: m/z calcd. for C33H41N2 11BF2Na [M + Na]+: 537.3223; found: 537.3224.