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Synlett 2010(20): 3035-3038  
DOI: 10.1055/s-0030-1259062
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Cyclizations of Aminyl Radicals Generated from Substoichiometric Stannane

Huimin Zhai, Jason G. Wickenden, Glenn M. Sammis*
Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada
Fax: +1(604)8220614; e-Mail: gsammis@chem.ubc.ca;
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Publication History

Received 16 September 2010
Publication Date:
24 November 2010 (online)

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Abstract

Substoichiometric amounts of tributyltin hydride were utilized in nitrogen-centered radical cyclizations onto silyl enol ethers for the formation of substituted cyclic imines.

Key words

aminyl radical cyclization - substoichiometric tributyltin hydride - silyl enol ethers - cyclic imines

    References and Notes

  • For reviews on nitrogen-centered radicals, see:
  • 1a Neale RS. Synthesis  1971,  1 
    Google Scholar
  • 1b Mackiewicz P. Furstoss R. Tetrahedron  1978,  34:  3241 
    Google Scholar
  • 1c Stella L. Angew. Chem., Int. Ed. Engl.  1983,  22:  337 
    Google Scholar
  • 1d Esker JL. Newcomb M. Adv. Heterocycl. Chem.  1993,  58:  1 
    Google Scholar
  • 1e Zard SZ. Synlett  1996,  1148 
    Google Scholar
  • 1f Fallis AG. Brinza IM. Tetrahedron  1997,  53:  17543 
    Google Scholar
  • 1g Zard SZ. Chem. Soc. Rev.  2008,  37:  1603 
    Google Scholar
  • 1h Curran DP. In Comprehensive Organic Synthesis   Vol. 4:  Trost BM. Fleming I. Pergamon Press; Oxford: 1991.  p.811 
    Google Scholar
  • 1i Stella L. In Radicals in Organic Synthesis   Vol. 2:  Renaud P. Sibi MP. Wiley-VCH; Weinheim: 2001.  p.407 
    Google Scholar
  • For initial studies, see:
  • 2a Kim S. Joe GH. Do JY.
    J. Am. Chem. Soc.  1993,  115:  3328 
    Google Scholar
  • 2b Kim S. Joe GH. Do JY. J. Am. Chem. Soc.  1994,  116:  5521 
    Google Scholar
  • 2c Minozzi M. Nanni D. Spagnolo P. Chem. Eur. J.  2009,  15:  7830 
    Google Scholar
  • 3 Zhai H. Zlotorzynska M. Sammis GM. Chem. Commun.  2009,  5716 
    CrossrefGoogle Scholar
  • 4 For a review of radical hydrogen transfer reactions, see: Robertson J. Pillai J. Lush RK. Chem. Soc. Rev.  2001,  30:  94 
    CrossrefGoogle Scholar
  • For representative examples of hydrogen abstraction α to amines, see:
  • 5a Routaboul L. Vanthuyne N. Gastaldi S. Gil G. Bertrand M. J. Org. Chem.  2008,  73:  364 
    Google Scholar
  • 5b El Blidi L. Nechab M. Vanthuyne N. Gastildi S. Bertrand M. Gil G. J. Org. Chem.  2009,  74:  2901 
    Google Scholar
  • 8 Benati L. Bencivenni G. Leardini R. Nanni D. Minozzi M. Spagnolo P. Scialpi R. Zanardi G. Org. Lett.  2006,  8:  2499 
    CrossrefGoogle Scholar
  • 11 Marco JL. J. Heterocycl. Chem.  1986,  1059 
    CrossrefGoogle Scholar
  • 12 Arai T. Abe H. Aoyagi S. Kibayashi C. Tetrahedron Lett.  2004,  45:  5921 
    CrossrefGoogle Scholar
6

For an example of an elimination of tributyltin radical from a carbon-centered radical α to a tin-bound amine, see ref. 2b.

7

We did not explore addition rates slower than 0.2 mL/h as the reaction times became prohibitively long.

9

While cyclization of azide 8 using 15 mol% of tributyltin hydride provided good conversion to the cyclized products, these conditions proved not to be robust for other substi-tution patterns. Cyclizations using 30 mol% tributyltin hydride proved to be general and reliable for all substrates examined.

10

We were also able to isolate 12% of the cis-isomer.