Download PDF
Synlett 2020; 31(18): 1817-1822
DOI: 10.1055/s-0040-1706414
letter
© Georg Thieme Verlag Stuttgart · New York

Selective Propargylation of Diaryl Azo Compounds Using Metallic Barium

Akira Yanagisawa∗
,
Toshihiko Heima
,
Kana Watanabe
,
Shun Haeno
Further Information

Publication History

Received: 17 June 2020

Accepted after revision: 13 July 2020

Publication Date:
17 August 2020 (online)

   Permissions and Reprints All articles of this category


Abstract

The Barbier-type propargylation of azo compounds with α,γ-disubstituted propargylic tosylates was achieved by using metallic barium as the promoter. Various propargylated hydrazines (α-adducts) were exclusively synthesized from the corresponding propargylic tosylates and azobenzenes (diaryldiazenes). The thus-obtained propargylic hydrazines were further efficiently converted into propargylic amines by reductive N–N bond cleavage. Benzidine rearrangement of the propargylic hydrazines was also attempted.

Key words

azo compounds - barium - hydrazines - propargylation - propargylic tosylates

Supporting Information

    Supporting information for this article is available online at https://doi.org/10.1055/s-0040-1706414.
  • Supporting Information
 

  • References and Notes

    • 1a Sell MS, Rieke RD. Synth. Commun. 1995; 25: 4107
      Crossref

      • For reviews, see:
    • 1b Rieke RD, Sell MS, Klein WR, Chen T.-A, Brown JD, Hanson MV. In Active Metals. Preparation, Characterization, Applications . Fürstner A. VCH; Weinheim: 1996: 1
      Google Scholar
    • 1c Rieke RD, Hanson MV. Tetrahedron 1997; 53: 1925
      Article in Thieme Connect
    • 2a Yanagisawa A, Okitsu S, Arai T. Synlett 2005; 1679
    • 2b Yanagisawa A, Suzuki T, Koide T, Okitsu S, Arai T. Chem. Asian J. 2008; 3: 1793
      CrossrefPubMed
  • 3 Yanagisawa A, Koide T, Yoshida K. Synlett 2010; 1515
    Article in Thieme Connect
  • 4 Yanagisawa A, Jitsukawa T, Yoshida K. Synlett 2013; 24: 635
    Article in Thieme Connect
  • 5 Yanagisawa A, Sawae T, Yamafuji S, Heima T, Yoshida K. Synlett 2015; 26: 1073
    Article in Thieme Connect
    • 6a Ma G, Xu Z, Zhang P, Liu J, Hao X, Ouyang J, Liang P, You S, Jia X. Org. Process Res. Dev. 2014; 18: 1169
      Crossref
    • 6b Fonseca TS, da Silva MR, de Oliveira MC. F, de Lemos TL. G, Marques RA, de Mattos MC. Appl. Catal., A 2015; 492: 76
      Crossref
    • 7a Fowler JS. J. Org. Chem. 1977; 42: 2637
      CrossrefPubMed
    • 7b Divya K, Narayana B. ISRN Spectrosc. 2014; 541970/1
  • 8 Yanagisawa A, Yamafuji S, Sawae T. Synlett 2016; 27: 2019
    Article in Thieme Connect

      • Prof. Miyoshi and co-workers have reported various reactions promoted by metallic strontium, see:
    • 9a Miyoshi N. In Science of Synthesis, Vol. 7. Yamamoto H. Thieme; Stuttgart: 2004: 685
      Google Scholar
    • 9b Miyoshi N, Ikehara D, Matsuo T, Kohno T, Matsui A, Wada M. J. Synth. Org. Chem., Jpn. 2006; 64: 845
      Crossref
    • 9c Miyoshi N, Matsuo T, Kikuchi M, Wada M. J. Synth. Org. Chem., Jpn. 2009; 67: 1274
      Crossref
    • 9d Miyoshi N, Kohno T, Wada M, Matsunaga S, Mizota I, Shimizu M. Chem. Lett. 2009; 38: 984
      Crossref
    • 9e Miyoshi N, Matsuo T, Mori M, Matsui A, Kikuchi M, Wada M, Hayashi M. Chem. Lett. 2009; 38: 996
      Crossref
    • 9f Miyoshi N, Asaoka M, Miyazaki Y, Tajima T, Kikuchi M, Wada M. Chem. Lett. 2012; 41: 35
      Crossref
  • 10 For a review of reductive N–N bond cleavage of hydrazines, see: Gilchrist TL. In Comprehensive Organic Synthesis, Vol. 8. Trost BM, Fleming I. Pergamon Press; Oxford: 1991: 388
    Google Scholar
  • 11 Sapountzis I, Knochel P. Angew. Chem. Int. Ed. 2004; 43: 897
    CrossrefPubMed
  • 12 Bunton CA, Rubin RJ. J. Am. Chem. Soc. 1976; 98: 4236
    Crossref

      • For reviews, see:
    • 13a Epsztein R. In Comprehensive Carbanion Chemistry, Chap. 3. Buncel E, Durst T. Elsevier; New York: 1984: 107
      Google Scholar
    • 13b Yamamoto H. In Comprehensive Organic Synthesis, Vol. 2. Trost BM, Fleming I, Heathcock CH. Pergamon Press; Oxford: 1991: 81
      Google Scholar
  • 14 Exactly what causes propargylic barium reagent 6 to react selectively at the α-carbon with azo compound 2 is not clear; however, the unusually long barium–carbon bond (2.76–2.88 Å) might prevent the formation of a six-membered cyclic transition-state model 10 leading to the γ-adduct, see: Kaupp M, Schleyer P. vR. J. Am. Chem. Soc. 1992; 114: 491
    Crossref
  • 15 Typical Experimental Procedure for the Barbier-Type Selective Propargylation of Diaryl Azo Compounds: Synthesis of 1-(6,6-Dimethylhept-4-yn-3-yl)-1,2-diphenylhydrazine (3ea, Table [2], Entry 2) Freshly cut barium (small pieces, 103.0 mg, 0.75 mmol), propargylic tosylate 1h (220.8 mg, 0.75 mmol), and azobenzene (45.6 mg, 0.25 mmol) were placed in a Schlenk tube (25 mL) under an argon atmosphere and covered with dry THF (1 mL). The mixture was stirred for 14 h at room temperature. The mixture was treated with sat. aq NH4Cl (10 mL), and the aqueous layer was extracted three times with Et2O (10 mL each). The combined organic extracts were washed with brine, dried over Na2SO4, and concentrated in vacuo after filtration. The residual crude product was purified by column chromatography on silica gel (hexane–MeOH, 50:1) to afford propargylic hydrazine 3ea (65.5 mg, 85% yield). 1H NMR (400 MHz, CDCl3): δ = 7.25–7.15 (m, 4 H, Ar–H), 7.05–7.03 (d, 2 H, J = 8.2 Hz, Ar–H), 6.91–6.85 (m, 3 H, Ar–H), 6.77–6.74 (t, 1 H, J = 7.3 Hz, Ar–H), 5.67 (br, 1 H, NH), 4.43–4.39 (t, 1 H, J = 7.5 Hz, CH), 1.89–1.66 (m, 2 H, CH2), 1.16 (s, 9 H, 3 CH3), 1.04–1.00 (t, 3 H, J = 7.4 Hz, CH3). 13C NMR (99.5 MHz, CDCl3): δ = 150.8, 149.0, 129.1, 128.9, 120.7, 118.9, 116.2, 112.1, 94.9, 75.1, 58.1, 31.4, 31.1, 27.4, 11.4. IR (neat): 3311, 2965, 2359, 1600, 1496, 1362, 1308, 1239, 1170, 1092, 1025, 992, 857, 819, 745, 691, 628 cm–1. MS (ESI): m/z calcd for [C21H27N2]+ [M + H]+: 307.2169; found: 307.2170; mp 57–60 °C.