Non-cryogenic metalation of aryl bromides bearing proton donating groups: Formation of a stable magnesio-intermediate

Tetrahedron Letters

Volumn 43, Issue 41, 2002, Pages 7315-7317

  Kato, Shinji ^a   Nonoyama, Nobuaki ^a   Tomimoto, Koji ^a   Mase, Toshiaki ^a  

^a BANYU PHARMACEUTICAL CO LTD   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

BENZOIC ACID DERIVATIVE; BROMINE DERIVATIVE; MAGNESIUM DERIVATIVE; METAL;

ARTICLE; CHEMICAL REACTION; METHODOLOGY; SYNTHESIS; TEMPERATURE;

EID: 0037037947     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(02)01747-1     Document Type: Article

References (19)

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9. . Bromine-lithium exchange of 1 with n-BuLi at lower temperature than -75°C was well studied by Parham and co-workers, see: Parham W.E., Bradsher C.K. Acc. Chem. Res. 15:1982;300-305.
10. ortho-Metalation of benzamide with alkyllithium has been conducted at -78°C. This protocol practically has some drawbacks such as tedious amidation/deamidation process and use of sec- or tert-BuLi (with handling difficulties). Direct metalation of benzoic acid with sec-BuLi/TMEDA at -90 to -78°C was also reported, see: Mortier, J.; Moyroud, J.; Bennetau, B.; Cain, P. A. J. Org. Chem. 1994, 59, 4042-4044. Direct method in a higher temperature range is still to be challenged.
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13. 3MgLi) for this case did not work well.
14. 3-mediated additions of the arylzinc compound prepared from methyl o-iodobenzoate to aldehydes at room temperature were reported, see: Ogawa Y., Saiga A., Mori M., Shibata T., Takagi K. J. Org. Chem. 65:2000;1031-1036.
15. Rathman T.L. Paquette L.A., Encyclopedia of Reagents for Organic Synthesis. 3:1995;1612-1613 John Wiley & Sons.
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17. 9% of the substrate 1 remained unreacted although 51% of the desired product 4 was obtained.
18. Considerable amount of protonated product (ca. 30%) was formed probably due to incomplete formation of the magnesium salt.
19. 4, the solvent was removed under reduced pressure, and the crude solid thus obtained was purified with silica gel chromatography (Wako gel™ C-300, EtOAc-heptane) to afford 3-phenylphthalide (4, 919 mg) as colorless crystals in 88% yield.