A convenient microwave assisted arylzinc generation-Negishi coupling protocol

Tetrahedron Letters

Volumn 45, Issue 20, 2004, Pages 3909-3912

  Mutule, Ilga ^a   Suna, Edgars ^a  

^a LATVIAN INSTITUTE OF ORGANIC SYNTHESIS   (Latvia)

Author keywords

Cross coupling; Microwaves; Nickel; Organometallic reagents; Palladium; Zinc

Indexed keywords

COPPER; IODIDE; ZINC;

ARTICLE; CATALYSIS; CHEMICAL REACTION KINETICS; HEATING; HYDROLYSIS; MICROWAVE IRRADIATION; SYNTHESIS; TEMPERATURE DEPENDENCE;

EID: 1942472067     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tetlet.2004.03.118     Document Type: Article

References (28)

1. Loupy A. Microwaves in Organic synthesis. 2002;Wiley-VCH, Weinheim.
2. Larhed M., Hallberg A. Drug Discov. Today. 6:2001;406.
3. Öhberg L., Westman J. Synlett. 2001;1893.
4. Stanetty P., Schnurch M., Mihovilovic M.D. Synlett. 2003;1862.
5. Whittaker A.G., Mingos D.M.P. J. Chem. Soc., Dalton Trans. 2002;3967.
6. Whittaker A.G., Mingos D.M.P. J. Chem. Soc., Dalton Trans. 2000;1521.
7. Negishi E. Palladium and nickel catalyzed reactions of organozinc compounds. Knochel P., Jones P. Organozinc Reagents. The Practical Approach in Chemistry Series. 1999;213-243 Oxford University Press, New York.
8. Erdik E. Tetrahedron. 48:1992;9577.
9. Most methods for direct generation of arylzinc species from aryl iodides and zinc suffer from relatively long reaction times (up to 24 h). On the other hand, the use of highly reactive Rieke zinc is associated with sophisticated handling techniques and therefore can hardly be automated. Subsequently, fast and operationally simple arylzinc preparation procedures are highly desirable, especially for high-throughput synthesis.
10. 3 Our experiments were performed on a purpose-built Smith Synthesizer by Personal Chemistry (Uppsala, Sweden) with a monomode cavity and temperature control.
11. Zinc dust was purchased from Acros.
12. 3,4 On the other hand, a successful application of Zn powder in a microwave environment to catalyze Friedel-Crafts acylation has been recently reported: Paul S., Nanda P., Gupta R., Loupy A. Synthesis. 2003;2877.
13. For a detailed description of GC analysis of zinc organometallics see: Knochel P., Jones P., Langer F. Organozinc chemistry: an overview and general experimental guidelines. Knochel P., Jones P. Organozinc Reagents. The Practical Approach in Chemistry Series. 1999;1-21 Oxford University Press, New York.
14. Newman M.S., Evans F.J. J. Am. Chem. Soc. 117:1995;946.
15. Yeh M.C.P., Chen H.G., Knochel P. Org. Synth. 70:1992;195.
16. Achyutha R.S., Knochel P. J. Am. Chem. Soc. 113:1991;5735.
17. Huo S. Org. Lett. 5:2003;423.
18. Petrier C., Dupuy C., Luche J.L. Tetrahedron Lett. 27:1986;3149.
19. Suarez R.M., Sestelo J.P., Sarandeses L.A. Synlett. 2002;1435.
20. The Zn-Cu couple was purchased from Aldrich and Acros. To the best of our knowledge, the use of a Zn-Cu couple for the generation of aryl zinc species is not precedented in the literature.
21. 2O (50 mL each). The solid material was ground in a pestle and after drying in vacuo for 8 h at 90°C the resulting dark grey zinc-copper couple was ready for use. No attenuation of activity of thus prepared Zn-Cu couple was observed after storage for 3 months under an argon atmosphere.
22. Extra dry DMF (Acros, water content < 50 ppm) was used in all experiments.
23. THF and DME were distilled from sodium benzophenone ketyl under argon.
24. Jiang B., Xu Y. J. Org. Chem. 56:1991;7336.
25. 1H NMR, GC-MS) and analytical data (melting points).
26. For relative rates of the formation of various arylzinc species see: Guijarro A., Rosenberg D.M., Rieke R.D. J. Am. Chem. Soc. 121:1999;4155.
27. Amano M., Saiga A., Ikegami R., Ogata T., Takagi K. Tetrahedron Lett. 39:1998;8667.
28. Experimental procedure for reactions in an oil bath. The temperature of the oil bath was adjusted to ensure a temperature of 130°C inside a well-stirred oven dried process vial (measured using a thermocouple thermometer with a hypodermic probe). An oven dried process vial equipped with a Teflon-coated stirring bar was charged with Zn-Cu couple (392 mg, 6.0 mmol), iodo-mesitylene 1i (246 mg, 1.0 mmol), flushed with argon and closed using open-top seals with a PTFE-faced septum. DMF (2 mL) was introduced via syringe and the reaction mixture was placed into the pre-heated oil bath. After the appropriate time the reaction mixture was cooled in an ice bath. Formation of mesitylzinc iodide 2i was determined by GC analysis of hydrolyzed and iodolyzed aliquots. Each datapoint on the curve (Fig. 1) represents a single experiment.