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Volumn 61, Issue 47, 2005, Pages 11168-11176

Arylzinc species by microwave assisted Grignard formation-transmetallation sequence: Application in the Negishi coupling

Author keywords

Grignard reagents; Microwaves; Negishi coupling; Organozinc reagents; Transmetallation

Indexed keywords

MAGNESIUM DERIVATIVE; ZINC DERIVATIVE;

EID: 27144473377     PISSN: 00404020     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tet.2005.09.022     Document Type: Article
Times cited : (34)

References (36)
  • 7
    • 27144554585 scopus 로고    scopus 로고
    • Microwave Assisted Preparation of Grignard and Organozinc Reagents
    • BOS, Vilnius, June 2002; Paper PO-49.
    • (a) For a preliminary report on microwave assisted generation of arylmagnesium species see: Mutule, I.; Avotina, D.; Suna E. Microwave Assisted Preparation of Grignard and Organozinc Reagents. Presented at the 2nd International conference on organic synthesis, BOS 2002, Vilnius, June 2002; Paper PO-49.
    • (2002) 2nd International Conference on Organic Synthesis
    • Mutule, I.1    Avotina, D.2    Suna, E.3
  • 8
    • 27144506616 scopus 로고    scopus 로고
    • note
    • (b) A single precedent of the preparation of 4-methoxyphenylmagnesium bromide under microwave dielectric heating has been reported in Ref. 3.
  • 9
    • 21544435209 scopus 로고    scopus 로고
    • (c) After submission of the manuscript, related work on microwave assisted generation of Grignard reagents was published: H. Gold, M. Larhed, and P. Nilsson Synlett 2005 1596
    • (2005) Synlett , pp. 1596
    • Gold, H.1    Larhed, M.2    Nilsson, P.3
  • 12
    • 84955056509 scopus 로고    scopus 로고
    • The Magnesium Route to Active Metals and Intermetallics
    • A. Fürstner VCH Weinheim
    • L.E. Aleandri, and B. Bogdanovic The Magnesium Route to Active Metals and Intermetallics A. Fürstner Active Metals 1996 VCH Weinheim 299 338
    • (1996) Active Metals , pp. 299-338
    • Aleandri, L.E.1    Bogdanovic, B.2
  • 13
    • 27144441771 scopus 로고    scopus 로고
    • See Ref. 7.
    • (a) See Ref. 7.
  • 15
    • 27144462642 scopus 로고    scopus 로고
    • note
    • Inert atmosphere and moisture free conditions, necessary for the Grignard generation can be easily realized in a Emrys™ microwave process vial closed with aluminum open-top seal with PTFE-faced septum.
  • 16
    • 27144519176 scopus 로고    scopus 로고
    • note
    • 2O, which are a routinely used medium for preparation of Grignard reagents. We were pleased to find that temperature and pressure profiles of the heating did not show any unusual behavior such as quick rise of temperature or sudden change of pressure, demonstrating that microwave irradiation of magnesium turnings under the tested conditions is safe and reliable procedure.
  • 17
    • 27144441447 scopus 로고    scopus 로고
    • note
    • THF was distilled from sodium benzophenone ketyl under argon prior to use.
  • 18
    • 0037970037 scopus 로고    scopus 로고
    • Organoalkali Chemistry
    • A. Schlosser Wiley Chichester
    • Prepared from 'dry ice' and dried by passing through concentrated sulfuric acid. Carbon dioxide has been frequently used as trapping agent to determine yields of organometallic species: see: M. Schlosser A. Schlosser Organoalkali Chemistry Organometallics in Synthesis: a Manual 2002 Wiley Chichester 1 353
    • (2002) Organometallics in Synthesis: A Manual , pp. 1-353
    • Schlosser, M.1
  • 19
    • 27144488187 scopus 로고    scopus 로고
    • note
    • During several 100 experiments performed, the pressure never exceeded 2 bar and none of over pressurization incidents were observed (the maximum pressure that could be employed in the system is 20 bar).
  • 20
    • 27144448496 scopus 로고    scopus 로고
    • note
    • The use of 80°C (vs 60°C) resulted in higher reproducibility of the Grignard formation.
  • 21
    • 0003998388 scopus 로고    scopus 로고
    • CRC
    • Dielectric constant of THF: 7.5 (at 22°C); dielectric constant of chlorobenzene: 5.7 (at 22°C); see: D.R. Lide CRC Handbook of Chemistry and Physics 2000 CRC 6 149
    • (2000) CRC Handbook of Chemistry and Physics , pp. 6-149
    • Lide, D.R.1
  • 22
    • 0037012872 scopus 로고    scopus 로고
    • Ionic liquids are among the most frequently employed additives; see, for example: N.E. Leadbeater, and H.M. Torenius J. Org. Chem. 67 2002 3145
    • (2002) J. Org. Chem. , vol.67 , pp. 3145
    • Leadbeater, N.E.1    Torenius, H.M.2
  • 23
    • 27144522033 scopus 로고    scopus 로고
    • note
    • Prepared by the reaction of excess magnesium with 1,2-dibromoethane, followed by removal of unreacted metal, then evaporation of solvent and, finally, drying of the solid residue in vacuo (0.1 Torr).
  • 24
    • 27144453370 scopus 로고    scopus 로고
    • note
    • 2 solution (1.0 M) was employed, precipitation of magnesium salts was observed.
  • 26
    • 27144446822 scopus 로고    scopus 로고
    • note
    • Dielectric heating at 180°C developed 13-19 bar pressure inside the Emrys™ microwave process vial. However, we never observed any of over pressurization incidents (the maximum pressure that could be employed in the system is 20 bar).
  • 28
    • 27144435889 scopus 로고    scopus 로고
    • note
    • 2, thus demonstrating the high chemoselectivity of the Negishi coupling over the 1,2-addition.
  • 29
    • 27144440894 scopus 로고    scopus 로고
    • note
    • 2 in THF (Aldrich) was employed.
  • 31
    • 27144513470 scopus 로고    scopus 로고
    • note
    • 2 (0.5 M solution in THF). Subsequent Negishi coupling with 4-bromobenzaldehyde 5 was completed at room temperature after 5 min (GC-MS assay). Further work is in progress to establish the role of Mg salts in the cross-coupling reaction.
  • 32
    • 27144510166 scopus 로고    scopus 로고
    • note
    • In the case of 4-dimethylamino-benzoic acid 2c the combined basic extracts were acidified with 1 M HCl to pH∼4. 0.1 M HCl was employed to acidify the basic extracts in the case of indoles 2g and 2i.


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