CC BY-ND-NC 4.0 · Synlett 2019; 30(04): 503-507
DOI: 10.1055/s-0037-1611669
letter
Copyright with the author

Manganese Catalyzed Asymmetric Transfer Hydrogenation of Ketones Using Chiral Oxamide Ligands

Jacob Schneekönig
,
,
Leibniz-Institut für Katalyse e.V., Albert-Einstein-Str. 29a, 18059 Rostock, Germany   Email: Matthias.Beller@catalysis.de
› Author Affiliations
This work was supported by the state of Mecklenburg Vorpommern.
Further Information

Publication History

Received: 14 December 2018

Accepted after revision: 10 January 2018

Publication Date:
25 January 2019 (online)


Published as part of the 30 Years SYNLETT – Pearl Anniversary Issue

Abstract

The asymmetric transfer hydrogenation of ketones using isopropyl alcohol (IPA) as hydrogen donor in the presence of novel manganese catalysts is explored. The selective and active systems are easily generated in situ from [MnBr(CO)5] and inexpensive C 2-symmeric bisoxalamide ligands. Under the optimized reaction conditions, the Mn-derived catalyst gave higher enantioselectivity compared with the related ruthenium catalyst.

Supporting Information

 
  • References and Notes

  • 3 Li Y.-Y, Yu S.-L, Shen W.-Y, Gao J.-X. Acc. Chem. Res. 2015; For a recent review on ATH including cobalt, see: 48: 2587
  • 4 Zhang G, Hanson SK. Chem. Commun. 2013; 10151
  • 8 Zirakzadeh A, de Aguiar SR. M. M, Stöger B, Widhalm M, Kirchner K. ChemCatChem 2017; 9: 1744
  • 9 Demmans KZ, Olson ME, Morris RH. Organometallics 2018; 37: 4608
  • 10 Wang D, Bruneau-Voisine A, Sortais J.-B. Catal. Commun. 2018; 105: 31
  • 12 Ligands L3b, L4a, L4b, L5, L6a and L6b were synthesized analogously to procedures described for related compounds, see: Şeker S, Barış D, Arslan N, Turgut Y, Pirinççioğlu N, Toğrul M. Tetrahedron: Asymmetry 2014; 25: 411 ; To a solution of the corresponding amino alcohol (2 mmol) in MeOH (4 mL) was added a solution dimethyl oxalate (1 mmol) in MeOH (2 mL) dropwise at room temperature. The resulting mixture was stirred for 30 min. Within this time, a cloudy white solid was formed. The solid was filtered off and washed with cold MeOH (2 × 2 mL) to give the analytically pure product.Analytical data found for L4b 1H NMR (300 MHz, DMSO-d6): δ = 7.96 (d, J = 8.2 Hz, 2 H), 7.29–7.19 (m, 10 H), 5.07–4.98 (m, 2 H), 3.60 (d, J = 5.3 Hz, 4 H), 3.29 (s, 6 H).13C NMR (75 MHz, DMSO-d6): δ = 159.30, 138.50, 128.66, 127.88, 126.86, 74.79, 59.12, 53.50.MS (ESI-TOF): m/z calcd 357.1814 [M+H]+, 379.1627 [M+Na]+; found: 357.1804 [M+H]+, 379.1627 [M+Na]+.L5 1H NMR (300 MHz, DMSO-d 6): δ = 9.07 (d, J = 9.0 Hz, 2 H), 7.41–7.10 (m, 10 H), 4.79–4.56 (m, 2 H), 2.03–1.60 (m, 4 H), 0.82 (t, J = 7.3 Hz, 6 H).13C NMR (75 MHz, DMSO-d 6): δ = 159.69, 142.88, 128.20, 126.89, 126.73, 54.99, 28.22, 11.20.MS (ESI-TOF): m/z calcd 347.1730 [M+Na]+; found: 347.1727 [M+Na]+.L6a 1H NMR (300 MHz, DMSO-d 6): δ = 8.86 (d, 2 H), 7.38–7.03 (m, 20 H), 5.06–4.91 (m, 2 H), 4.91–4.81 (m, 2 H).13C NMR (75 MHz, DMSO-d 6): δ = 159.74, 140.25, 128.16, 127.05, 127.01, 63.95, 55.74.MS (ESI-TOF): m/z calcd 503.1941 [M+Na]+; found: 503.1945 [M+Na]+.L6b 1H NMR (300 MHz, DMSO-d 6): δ = 8.90–8.68 (m, 2 H), 7.41–7.05 (m, 20 H), 5.03–4.74 (m, 4 H).13C NMR (75 MHz, DMSO-d 6): δ = 158.99, 142.87, 140.13, 128.60, 128.05, 127.54, 127.36, 127.09, 74.10, 59.46, 74.10, 59.46.MS (ESI-TOF): m/z calcd 503.1941 [M+Na]+; found 503.1949 [M+Na]+
  • 13 Ligands L3a, L3c, and L7 were synthesized analogously to the procedure described for related compounds, see: Woods BP, Orlandi M, Huang CY, Sigman MS, Doyle AG. J. Am. Chem. Soc. 2017; 139: 5688 ; The corresponding amino alcohol (1 mmol) and dimethyl oxalate (1 mmol) were added under a flow of argon into a flame-dried 25 mL Schlenk tube containing a PTFE-coated stirring bar. Toluene (10 mL) was added by using a syringe and the suspension was heated to 90 °C. After 3 h, the mixture was allowed to cool to room temperature and the volatiles were removed in vacuo. The resulting solid was washed with cold toluene (2 × 2 mL) to give the analytically pure product.Analytical data found for L3c 1H NMR: δ = 8.05 (d, J = 9.8 Hz, 2 H), 3.74–3.40 (m, 6 H), 0.87 (s, 18 H).13C NMR (75 MHz, DMSO-d 6): δ = 160.21, 59.90, 59.41, 33.93, 26.86.MS (ESI-TOF): m/z calcd 289.2127 [M+H]+, 311.1941 [M+Na]+; found: 289.2120 [M+H]+, 311.1944 [M+Na]+.L7 1H NMR (300 MHz, DMSO-d 6): δ = 9.10 (s, 2 H), 7.30–6.94 (m, 8 H), 5.16–5.03 (m, 2 H), 4.58–4.41 (m, 2 H), 3.21–3.12 (m, 2 H), 2.78–2.69 (m, 2 H).13C NMR: (75 MHz, DMSO-d 6): δ = 160.60, 141.16, 139.79, 127.66, 126.63, 124.66, 123.59, 76.91, 61.43, 40.20 (shoulder of DMSO signal).MS (ESI-TOF): m/z calcd 352.1423 [M]+; found: 352.1429 [M]+
  • 14 Denmark SC, Stavenger RA, Faucher A.-M, Edwards JP. J. Org. Chem. 1997; 62: 3375
  • 15 Gao J.-X, Ikariya T, Noyori R. Organometallics 1996; 15: 1087
  • 17 General procedure for the ATH of prochiral ketones: Ligand L4a (6.6 mg, 0.02 mmol, 2 mol%) and MnBr(CO)5 (16.2 mg, 0.06 mmol, 6 mol%) were placed in a flame-dried 25 mL Schlenk tube equipped with a PTFE-coated stirring bar, followed by anhydrous degassed isopropyl alcohol (2 mL). The suspension was stirred for 10 min at room temperature. A solution of potassium tert-butoxide (22.4 mg, 0.2 mmol, 20 mol% in 2 mL iPrOH) was added and the resulting yellowish solution was stirred for a further 10 min at room temperature. A solution of the desired ketone (1 mmol in 2 mL iPrOH) was then added and the mixture was heated to 80 °C and kept at this temperature for 20 h. The reaction solution was allowed to cool to room temperature and filtered through a plug of silica and washed with iPrOH (3 × 5 mL). Hexadecane (20 mg) was added to the reaction solution. The yield of the desired alcohol was determined by GC analysis using hexadecane as internal standard, and the ee was determined either by GC or HPLC analysis using an appropriate separation method (see the Supporting Information for further information).