Synlett
DOI: 10.1055/s-0036-1588554
letter
© Georg Thieme Verlag Stuttgart · New York

m-C2B10H11HgCl/AgOTf-Catalyzed Reaction for Reductive Deoxygenation

Naoto Yamasaki, Marina Kanno, Kyohei Sakamoto, Yusuke Kasai, Hiroshi Imagawa, Hirofumi Yamamoto*
  • Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770-8514, Japan   Email: hirofumi@ph.bunri-u.ac.jp
This study was financially supported by a Grant-in-Aid (No. 23790034) from the MEXT (Ministry of Education, Culture, Sports, Science, and Technology) of the Japanese Government.
Further Information

Publication History

Received: 01 July 2017

Accepted after revision: 25 July 2017

Publication Date:
29 August 2017 (eFirst)

Abstract

A m-C2B10H11HgCl/AgOTf-catalyzed reaction of allyl silyl ethers with N-Boc-N′-tosylhydrazine has been developed. Under mild conditions, the resulting allyl hydrazine products were transformed into naked alkenes in good yield. Furthermore, the used m-C2B10H11HgCl could be recovered quantitatively.

Supporting Information

 
  • References and Notes

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  • 16 Product 16 was obtained as the mixture of rotamers; see Supporting Information.
  • 17 Preparation of 0.1 M CH2Cl2 Solution of m-C2B10H11HgCl/AgOTf To a suspension of AgOTf (38.5 mg, 0.150 mmol) in CH2Cl2 (1.5 mL) was added m-C2B10H11HgCl (56.9 mg, 0.150 mmol) at r.t., and the mixture was stirred at r.t. for 30 min. Typical Procedure for the m-C2B10H11HgCl/AgOTf-Catalyzed Allylic Amination (Table 1, Entry 12) A solution of (E)-tert-butyldiphenyl(undec-6-en-5-yloxy)silane (15b, 1.08 g, 2.64 mmol) and tert-butyl 2-tosylhydrazine-1-carboxylate (12, 755 mg, 3.96 mmol) in CH2Cl2 (8.7 mL) was added to a dried two-neck flask under an atmosphere of argon. m-C2B10H11HgCl/AgOTf in 0.1 M CH2Cl2 (1.32 mL) was added dropwise to the solution at 0 °C, and the mixture was stirred at 0 °C for 10 min. The reaction was quenched with sat. NaCl aq, and the organic phase was separated. The aqueous phase was extracted with CH2Cl2 (3 ×). The combined organic phase was dried over MgSO4 and concentrated in vacuo. The residue was purified by silica gel chromatography (hexane/AcOEt = 20:1 to 4:1) to give 16 (902 mg, 2.06 mmol, 78%) along with m-C2B10H11HgCl (48.2 mg, 0.127 mmol, 96%). Analytical Data for Compound 16 Colorless syrup. FT-IR (neat): 3313, 3238, 3138, 2957, 2929, 2857, 2856 cm–1. 1H NMR (500 MHz, DMSO, 70 °C): δ = 0.85 (6 H, m), 1.25 (20 H, m), 1.93 (3 H, m), 2.43 (3 H, s), 4.18 (1 H, br d, J = 6.0 Hz), 5.27 (1 H, m), 5.47 (1 H, m), 7.36 (2 H, d, J = 7.5 Hz), 7.79 (2 H, d, J = 7.5 Hz), 8.59 (NH, br s). 13C NMR (125 MHz, DMSO, 70 °C): δ = 14.06, 21.36, 21.96, 22.18, 27.92, 28.13, 28.25, 28.47, 30.92, 31.68, 32.38, 62.06, 80.09, 128.22, 128.60, 129.55, 129.67, 143.80, 155.48. MS (CI): m/z = 437 [M – H]+. HRMS (CI+): m/z calcd for C23H39N2O4S: 437.2474; found: 437.2479.
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  • 21 Typical Procedure for the Selective Cleavage of Boc-Protecting Group and the Transformation into Alkene (Scheme 3, a) A 1.0 M HCl in AcOEt (6.2 mmol, 6 mL) was added to a solution of 16 (156 mg, 0.310 mmol) in AcOEt (0.31 mL) at r.t. The reaction mixture was stirred for 5 h at r.t. It was diluted with Et2O and then quenched with sat. NaHCO3 aqueous solution. The aqueous phase was extracted with Et2O (3 ×). The combined organic phase was dried over Na2SO4, and concentrated in vacuo to give 17 (105 mg, 0.310 mmol, quant.) as a crude product. Analytical Data for Compound 17 Yellow syrup. FT-IR (neat): 3368, 3029, 2956, 2928, 2870, 2858 cm–1. 1H NMR (300 MHz, CDCl3): δ = 0.87 (6 H, m), 1.13–1.33 (8 H, m), 1.52–1.67 (2 H, m), 1.86 (2 H, q, J = 6.6 Hz), 2.42 (3 H, s), 3.40 (NH2, s), 4.39, (1 H, q, J = 7.5 Hz), 5.18 (1 H, ddd, J = 1.5 Hz, 7.5 Hz, 15.6 Hz), 5.50 (1 H, dt, J = 6.6 Hz, 15.6 Hz), 7.29 (2 H, d, J = 7.8 Hz), 7.73 (2 H, d, J = 7.8 Hz). 13C NMR (75 MHz, CDCl3): δ = 13.86, 14.00, 21.48, 22.11, 22.28, 28.28, 31.05, 31.65, 31.95, 60.35, 125.44, 128.25, 128.37, 134.54, 134.94, 143.51. MS (Cl): m/z = 339 [M + H]+. HRMS (CI+): m/z calcd for C18H31N2O2S: 339.3006; found: 339.2907. Next, neutral silica gel (3.0 g) was added to a solution of 17 (105 mg, 0.310 mmol) in AcOEt (6 mL), and it was stirred for 6 h at r.t. It was filtrated and washed with hexane/AcOEt (100:1), and the filtrate was concentrated in vacuo. The residue was purified by silica gel chromatography (hexane/AcOEt = 100:1) to give (E)-undec-5-ene (19, 39.2 mg, 0.254 mmol, 82% from 16). Analytical Data for Compound 19 Colorless syrup. FT-IR (neat): 2957, 2931, 2871 cm–1. 1H NMR (400 MHz, CDCl3): δ = 0.88 (6 H, m), 1.27 (10 H, m), 1.97 (4 H, m), 5.39 (2 H, m). 13C NMR (100 MHz, CDCl3): δ = 14.31, 14.43, 22.54, 22.90, 29.689, 31.75, 32.18, 32.64, 32.93, 130.64, 130.71. MS (Cl): m/z = 154 [M]+. HRMS (CI+): m/z calcd for C11H22: 154.1722; found: 154.1720.
  • 22 One-Pot Synthesis of Alkene 19 from 15b (Scheme 3, b) A solution of 15b (129 mg, 0.316 mmol) and 12 (136 mg, 0.474 mmol) in CH2Cl2 (0.85 mL) was added to a dried two-neck flask under an atmosphere of argon. m-C2B10H11HgCl/AgOTf in 0.1 M CH2Cl2 (158 μL) was added dropwise to the solution at 0 °C, and it was stirred at 0 °C for 10 min. Subsequently, a 1.0 M HCl in AcOEt (5.0 mL) was added to the mixture at r.t., and it was stirred at r.t. until disappearance of 16. Next, neutral silica gel (3.0 g) was added to the mixture, which was stirred for 24 h at r.t. The suspension was filtrated and washed with hexane/AcOEt (4:1). The filtrate was concentrated in vacuo. The residue was purified by silica gel chromatography (hexane/AcOEt = 100:1 to 4:1) to give 19 (31.2 mg, 0.202 mmol, 64% from 15b) along with m-C2B10H11HgCl (5.9 mg, 15.6 μmol, 99%).

    • See Supporting Information. For review of NHK reaction, see:
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    • 23b Cintas P. Synthesis 1992; 248
  • 24 CCDC 1556661 contains the supplementary crystallographic data for this paper. The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/getstructures.
  • 25 Myers AG. Kukkola PJ. J. Am. Chem. Soc. 1990; 112: 8208