2,2′-Bipyridine: An Efficient Ligand in the Cobalt-Catalyzed Synthesis of Organozinc Reagents from Aryl Chlorides and Sulfonates

Abstract

The synthesis of functionalized arylzinc reagents from aromatic chlorides, triflates, or mesylates, via cobalt catalysis, is reported using 2,2′-bipyridine as a ligand in a mixture of acetonitrile and pyridine. This procedure allows the synthesis of a variety of functionalized arylzinc species in good to excellent yields. Some of these arylzinc compounds have been coupled with aromatic bromides under palladium catalysis.

cobalt halide - catalysis - zinc - aromatic chlorides - trif­lates

References and Notes

1a Knochel P. Singer RD. Chem. Rev.  1993,  93:  2117 

1b Knochel P. Almena Perea JJ. Jones P. Tetrahedron  1998,  54:  8275 

2a Sibille S. Ratovelomanana V. Périchon J. J. Chem. Soc., Chem. Commun.  1992,  283 

2b Sibille S. Ratovelomanana V. Nédélec JY. Périchon J. Synlett  1993,  425 

2c Gosmini C, Rollin Y, and Périchon J. inventors; WO Patent  WO0102626. 

2d Gosmini C. Rollin Y. Nédélec JY. Périchon J. J. Org. Chem.  2000,  65:  6024 

2e Le Gall E. Gosmini C. Nédélec JY. Périchon J. Tetrahedron  2001,  57:  1923 

2f Fillon H. Gosmini C. Nédélec JY. Périchon J. Tetrahedron Lett.  2001,  42:  3843 

3 Littke AF. Fu GC. Angew. Chem. Int. Ed.  2002,  41:  4176 

4a Zapf A. Beller M. Top. Catal.  2002,  19:  101 

4b Tucker CE. de Vries JG. Top. Catal.  2002,  19:  111 

5a Fillon H. Gosmini C. Périchon J. J. Am. Chem. Soc.  2003,  125:  3867 

5b Kazmierski I. Gosmini C. Paris JM. Périchon J. Tetrahedron Lett.  2003,  44:  6417 

6 Buriez O. Nédélec J.-Y. Périchon J. J. Electroanal. Chem.  2001,  506:  162 

7 Seka S. Buriez O. Périchon J. Chem. Eur. J.  2003,  9:  3597 

8 Gosmini C. Amatore M. Claudel S. Périchon J. Synlett  2005,  2171 

9 Amatore M. Gosmini C. Périchon J. Eur. J. Org. Chem.  2005,  989 

10a Penney JM. Miller JA. Tetrahedron Lett.  2004,  45:  4989 

10b Miller JA. Dankwardt JW. Penney JM. Synthesis  2003,  1643 

10c Miller JA. Dankwardt JW. Tetrahedron Lett.  2003,  44:  1907 

10d Garcia JJ. Brunkan NM. Jones WD. J. Am. Chem. Soc.  2002,  124:  9547 

10e Taw FL. White PS. Bergman RG. Brookhart M. J. Am. Chem. Soc.  2002,  124:  4192 

10f Miller JA. Tetrahedron Lett.  2001,  42:  6991 

10g Abla M. Yamamoto T. J. Organomet. Chem.  1997,  532:  267 

11 The procedure for the synthesis of mesylates and triflates is based on: Mowery ME. DeShonh P. J. Org. Chem.  1999,  64:  3266 

12

Functionalized Mesylates or Triflates; Typical Procedure Phenol (5.3 g, 50 mmol) and pyridine (22 mL) were cooled to 0 °C in a three-way reaction vessel under an argon atmosphere. Tf₂O (8.5 mL, 50 mmol) was added dropwise over 45 min to the magnetically stirred solution, giving rise to a strong red-orange color. Then the reaction mixture was stirred at r.t. until the starting phenol had been consumed (monitored by GC on hydrolyzed aliquots). H₂O (40 mL) was added to the mixture, which was then extracted with CH₂Cl₂ (3 × 40 mL). The organic layer was treated with 10% HCl (40 mL), washed with a sat. solution of NaCl (40 mL), and dried over anhyd MgSO₄. After removing the solvent under vacuum, the product was purified by flash chromatography on silica gel (pentane) to give phenyl trifluoromethanesulfonate in 95% yield as a colorless oil.
The same procedure was applied to the synthesis of mesylates, by replacing Tf₂O with MsCl. Coupling of Organozinc Chlorides or Triflates with 2-Bromopyridine; Typical Procedure (Table 1, entry 1)
Preliminary Step: Zn powder (1.27 g, 1.95 equiv, <10 µm) and CoBr₂ (219 mg, 0.1 equiv) were placed in a reaction vessel under an argon atmosphere. MeCN (6 mL), allyl chloride (0.25 mL, 0.3 equiv), dodecane (0.2 mL, internal reference for GC), and TFA (0.05 mL) were added in one batch to the vessel. The resulting reaction mixture was magnetically stirred under a flow of argon at r.t. for 3 min.
Synthesis of the Organozinc Reagent: Pyridine (4 mL), 2,2′-bipyridine (0.156 g, 0.1 equiv), and methyl 4-chlorobenzo-ate (1.71 g, 10 mmol) were added to the reaction mixture, and stirred at 50 °C until the reaction was complete (aliquots were removed, monitored by GC after iodination). After 3 h, 4-carboxymethylzinc chloride was obtained in 86% yield (GC).
Coupling Reaction: DMF or THF (5 mL), 2-bromopyridine (1 mL, 1 equiv) and PdCl₂(PPh₃)₂ (70 mg, 0.01 equiv) were added to the reaction mixture obtained above, and the resulting solution was stirred for 3 h at 50 °C until 4-car-boxymethylzinc chloride had been completely consumed. The solution was hydrolyzed with NH₄Cl (100 mL), extracted with Et₂O, the organic layer was washed with brine, dried, and the solvent evaporated. The residue was isolated by flash column chromatography (silica gel; pentane-Et₂O, 85:15) to give the Negishi coupled product in 73% yield. The structure was confirmed by ¹H and ¹³C NMR spectroscopy and MS.

13 Negishi EI. Acc. Chem. Res.  1982,  15:  340 

14a Korn TJ. Knochel P. Angew. Chem. Int. Ed.  2005,  44:  2947 

14b Korn TJ. Cahiez G. Knochel P. Synlett  2003,  1892 

14c Korn TJ. Schade MA. Wirth S. Knochel P. Org. Lett.  2006,  8:  725 

14d Shinokubo H. Oshima K. Eur. J. Org. Chem.  2004,  2081