A Planar-Chiral Pillar[5]arene-Based Monophosphine Ligand with Induced Chirality at the Biaryl Axis

Published as part of the Cluster Atropisomerism – in Memoriam Kurt Mislow

Abstract

A planar-chiral pillar[5]arene with cyclohexylmethoxy side chains and a pendant diphenylphosphine was prepared and used as a chiral ligand in asymmetric reactions. Chirality transfer from the planar-chiral pillar[5]arene scaffold to the chiral biaryl moiety was demonstrated by circular dichroism (CD) spectroscopy, single-crystal X-ray diffraction analysis, and asymmetric catalysis.

Key words

pillar[5]arene - planar chirality - circular dichroism - chiral ligand

• References and Notes

• 1 Ogoshi T. Kanai S. Fujinami S. Yamagishi TA. Nakamoto Y. J. Am. Chem. Soc. 2008; 130: 5022
• 2a Xue M. Yang Y. Chi XD. Zhang ZB. Huang FH. Acc. Chem. Res. 2012; 45: 1294
• 2b Ogoshi T. Yamagishi T. Eur. J. Org. Chem. 2013; 2961
• 2c Strutt NL. Zhang HC. Schneebeli ST. Stoddart JF. Acc. Chem. Res. 2014; 47: 2631
• 2d Ogoshi T. Yamagishi TA. Nakamoto Y. Chem. Rev. 2016; 116: 7937
• 3 Ogoshi T. Masaki K. Shiga R. Kitajima K. Yamagishi TA. Org. Lett. 2011; 13: 1264
• 4a Ogoshi T. Ueshima N. Yamagishi T. Org. Lett. 2013; 15: 3742
• 4b Liz DG. Manfredi AM. Medeiros M. Montecinos R. Gomez-Gonzalez B. Garcia-Rio L. Nome F. Chem. Commun. 2016; 3167
• 4c Xiao XD. Bai YL. Liu JQ. Wang JW. Tetrahedron Lett. 2016; 57: 3385
• 4d Liu YZ. Lou BH. Shangguan LQ. Cai JS. Zhu HT. Z. Shi BB. Macromolecules 2018; 51: 1351
• 4e Wanderlind EH. Liz DG. Gerola AP. Affeldt RF. Nascimento V. Bretanha LC. Montecinos R. Garcia-Rio L. Fiedler HD. Nome F. ACS Catal. 2018; 8: 3343
• 5 Hayashi T. Acc. Chem. Res. 2000; 33: 354
• 6a Suginome M. Yamamoto T. Nagata Y. Yamada T. Akai Y. Pure Appl. Chem. 2012; 84: 1759
• 6b Suginome M. Yamamoto T. Nagata Y. J. Synth. Org. Chem. Jpn. 2015; 73: 1141
• 7a Yamamoto T. Suginome M. Angew. Chem. Int. Ed. 2009; 48: 539
• 7b Yamamoto T. Yamada T. Nagata Y. Suginome M. J. Am. Chem. Soc. 2010; 132: 7899
• 8 Mislow K. Siegel J. J. Am. Chem. Soc. 1984; 106: 3319
• 9a Yamamoto T. Akai Y. Nagata Y. Suginome M. Angew. Chem. Int. Ed. 2011; 50: 8844
• 9b Akai Y. Yamamoto T. Nagata Y. Ohmura T. Suginome M. J. Am. Chem. Soc. 2012; 134: 11092
• 9c Yamamoto T. Akai Y. Suginome M. Angew. Chem. Int. Ed. 2014; 53: 12785
• 9d Akai Y. Konnert L. Yamamoto T. Suginome M. Chem. Commun. 2015; 7211
• 10 Ogoshi T. Furuta T. Yamagishi T. Chem. Commun. 2016; 10775
• 11 Compound 7: Precursor 6 (110 mg, 65.0 μmol), diphenylphosphine oxide (30.3 mg, 0.150 mmol), Pd(OAc)₂ (1.53 mg, 6.80 μmol), and 1,4-bis(diphenylphosphino)butane (2.90 mg, 6.80 μmol) were dissolved in a mixture of diisopropylethylamine (iPr₂NEt, 142 μL, 0.810 mmol) and dimethyl sulfoxide (816 μL) under a nitrogen atmosphere. The reaction mixture was stirred at 120 °C for 16 h. After cooling to room temperature, aq. HCl (1.0 M) and CH₂Cl₂ were added to the mixture. The organic phase was separated from aqueous phase, washed with water, and dried over MgSO₄. After filtration and evaporation of the solvent, the residue was subjected to silica gel column chromatography (n-hexane/ethyl acetate, 4:1) to give 7 (93.9 mg, 83% yield); m.p. 135.5–135.8 °C. Compound 8: To a solution of 7 (86.8 mg, 500 μmol) and trimethylamine (139 μL, 1.00 mmol) in toluene (1.25 mL) was added trichlorosilane (51 μL, 500 μmol) at 0 °C. The resulting solution was heated at 80 °C for 24 h. After cooling to room temperature, the solvent was removed by evaporation. To the residue were added aq. NaOH (1.0 M) and saturated aq. NaHCO₃. The organic phase was separated, washed with water, and dried over MgSO₄. After filtration and evaporation of the solvent, the residue was subjected to silica gel column chromatography (n-hexane/ethyl acetate, 20:1) to give 8 (67.3 mg, 76% yield). The melting point of 8 was not determined due to the oxidation of the phosphine group during the procedure.
• 12 Hayashi T. Hirate S. Kitayama K. Tsuji H. Torii A. Uozumi Y. J. Org. Chem. 2001; 66: 1441