References
- Farina , V. , Baker , S. R. and Sapino , C. 1988 . Tetrahedron Lett. , 29 : 6043 U. S. Patent 4,870, 168, Cook, G. K.;Hornback, W. J., Jordan, C. L., McDonald, J. H., Munroe, J. E. J. Org. Chem. 1989, 54, 5828
- Scott , W. J. and Stille , J. K. 1986 . J. Am. Chem. Soc. , 108 : 3033
- A 98:2 cisrtrans mixture of Z-(1)-propenyl-tributylstannane affords the coupled cephem with the corresponding 98:2 cis:trans ratio
- Beletskaya , I. P. 1983 . J. Organomet. Chem , 250 : 551
- Gielen , M. and Nasielski , J. 1972 . Organotin Compd. , 3 : 625 Polar solvents are known to play an important role in electrophilic cleavage of carbon-tin bonds:
- Eaborn , C. , Odell , R. J. and Pidcock , A. 1978 . J. Chem. Soc Dalton Trans , : 357 Labadie, J. W., Stille, J. K., J. Am. Chem. Soc. 1983, 105, 6129, Milstein, D., Stille, J. K., J. Org. Chem. 1979, 44, 1613
- Piers , E. 1986 . Friesen J. Org. Chem. , 51 : 3405 Piers, E., Friesen, R. W., Keay, B. A., J. Chem. Soc. Chem. Commun. 1985, 809
- Kanemoto , S. , Matsubara , S. , Oshima , K. , Utimoto , K. and Nozaki , H. 1987 . Chem Lett. , : 5 Tolstikov, G. A., Miftakhou, M. S., Danilova, N., A., Velder, Y. L., Spirikhin, L. V., Synthesis 1989, 633
- Mechanistic cycles proposed by Stille (Pure and Appl. Chem. 1985, 57, 1771.) claim that added halide such as LiCl is a strict requirement: “apparently the vinyl palladium chloride is required for the transmetallation reaction, as palladium triflates will not undergo transmetallation with vinyltin readily” however, it has recently been demonstrated that Pd-OTf bonds are labile (103, more than Cl) and can be displaced by most polar solvents as ligands: Diver, C, Lawrance, G. A., J. Chem. Soc. Dalton Trans. 1988, 931. Procedure for coupling reactions: A mixture of 293 mg (0.5 mmole) of p-methoxybenzyl 7-phenylacetamido-3-(trifluoromethylsulfonyloxy)-3-cephem-4-carboxylate, 190 mg (0.6 mmole) of vinyl tri-n-butylstannane and 11.2 mg (0.05 mmole) of palladium (II) acetate in 1.0 mL of 1-methyl-2-pyrrolidinone was stirred in at room temperature for 3 min. The reaction mixture was diluted with ethyl acetate, washed (2x) with water and the organic fraction was dried and concentrated. The residue was redissolved in ethyl acetate and the organic solution stirred with carbon for 1 hr. The carbon was removed by filtration and the filtrate evaporated. The residue was crystallized from methanol to produce 0.129 g (55.5%) of the desired compound (Entry 1)