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Volumn 51, Issue 1, 2010, Pages 174-176

The superiority of properly prepared lithium 1-N,N-dimethylaminonaphthalenide (LDMAN) over other aromatic radical-anions for the generation of organolithiums by reductive lithiation

Author keywords

[No Author keywords available]

Indexed keywords

AROMATIC COMPOUND; LITHIUM 1 N,N DIMETHYLAMINONAPHTHALENIDE; LITHIUM DERIVATIVE; ORGANOLITHIUM COMPOUND; UNCLASSIFIED DRUG;

EID: 70649083233     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tetlet.2009.10.121     Document Type: Article
Times cited : (7)

References (62)
  • 7
    • 70649102538 scopus 로고    scopus 로고
    • In the earliest reports of the reductive lithiation of phenyl thioethers, there were several examples in which a sub-stoichiometric quantity of naphthalene was used along with a stoichiometric quantity of lithium metal: see Ref. 1a and (a) Screttas, C. G.; Micha-Screttas, M. J. Org. Chem. 1979, 44, 713-719. More recently, Yus's group has extensively utilized a form of the catalytic method in which a large excess of lithium is used along with a catalytic amount of the aromatic, usually naphthalene or p,p′-di-tert-butylbiphenyl: (b) Yus, M., In The Chemistry of Organolithium Compounds, Rappoport, Z. Marek, I., Ed.; Wiley: Chichester, 2004; Part 2, Chapter 11; (c) Ramón, D. J.; Yus, M. Eur. J. Org. Chem. 2000, 225-237.
    • In the earliest reports of the reductive lithiation of phenyl thioethers, there were several examples in which a sub-stoichiometric quantity of naphthalene was used along with a stoichiometric quantity of lithium metal: see Ref. 1a and (a) Screttas, C. G.; Micha-Screttas, M. J. Org. Chem. 1979, 44, 713-719. More recently, Yus's group has extensively utilized a form of the catalytic method in which a large excess of lithium is used along with a catalytic amount of the aromatic, usually naphthalene or p,p′-di-tert-butylbiphenyl: (b) Yus, M., In The Chemistry of Organolithium Compounds, Rappoport, Z. Marek, I., Ed.; Wiley: Chichester, 2004; Part 2, Chapter 11; (c) Ramón, D. J.; Yus, M. Eur. J. Org. Chem. 2000, 225-237.
  • 48
  • 57
    • 70649095633 scopus 로고    scopus 로고
    • note
    • In some cases this was due to the sensitivity of the product of electrophile capture to the acid that was used to remove the dimethylaminonaphthalene byproduct: Brockunier, L. L., MS Thesis, University of Pittsburgh, 1988, p 21. However, even when the product is not acid-sensitive, some preliminary trials had indicated that LDBB gave superior results.
  • 59
    • 49049131007 scopus 로고    scopus 로고
    • note
    • 3,11 However, occasional irreproducibility and poor yields (for one literature example, see: Paquette, L. A.; Horn, K. A.; Wells, G. J. Tetrahedron Lett. 1982, 23, 259-262) led to speculation that lower temperatures may lead to better results and starting in 1999, the temperature of -55 °C was generally aimed for during the generation of LDMAN, although careful temperature control was not generally sought; apparently the first example was the lower temperature to prepare LDMAN only for the synthesis of 24 in: Chen, F.; Mudryk, B.; Cohen, T. Tetrahedron 1999, 55, 3291-3304. However, most other groups that have reported the use of LDMAN are still using the original recipe.
  • 60
    • 70649110360 scopus 로고    scopus 로고
    • note
    • There may be automatic temperature controllers that can maintain the required narrow range, but we are unaware of any at this time.
  • 61
    • 70649114013 scopus 로고    scopus 로고
    • note
    • General procedure for the reductive lithiation with LDMAN; To a three-neck round bottomed flask, equipped with a magnetic stirrer, argon inlet and a rubber septum was added 40 mL of dry THF. The flask was cooled to -55 °C. Lithium ribbon was prepared by scraping the dark oxide coating off of the surface while it was immersed in fresh mineral oil. The shiny metal was dipped into dry hexane in order to remove the oil and then weighed (0.1852 g, 0.0268 mol) in a tared beaker containing mineral oil. The metal was sliced into small pieces while it was still immersed in mineral oil. The lithium pieces were dipped again in hexane prior to the addition to the flask. Then DMAN (4.9 mL, 0.030 mol) was added quickly via syringe at -55 °C. A green color appeared in less than two minutes and became deep green in less than 5 min. The reaction mixture was stirred for 5 h at -55 ± 3 °C, and the resulting LDMAN solution was suitable for reductive lithiation of 0.0127 mol of substrate.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.