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Experiment 4, page 3

Experimental Procedure

In a 100 ml 3-necked flask are placed 4-bromonitrobenzene (2.02 g 10 mmol), phenylethyne (1.53 g, 1.65 ml, 1.5 eq.), palladium (II) acetate (2.8 mg, 0.12 mol%), triphenylphosphine (6.6 mg, 0.25 mol%), triethylamine (20 ml) and a magnetic stirrer bar. The flask is fitted with a condenser, attached to a N₂supply with a pressure relief bubbler, and the two remaining ports stoppered after the flask has been purged with N₂. The solution is stirred and heated gently to 100ºC for 75 min. The exothermic reaction will initially cause vigorous boiling, but this will subside as the reaction nears completion.
The reaction mixture is cooled to room temperature and 2Mhydrochloric acid (42 ml) added. The insoluble product is collected by filtration and dried in a drying pistol overnight. The product is then sublimed at ~115ºC at 2-3 mmHg. The sublimate is dissolved in ~70% ethanol/water and left in a fridge overnight to complete crystallisation. The crystals are finally collected and dried in vacuo.
Record the yield, m.p., i.r. and n.m.r. spectra and give full interpretations of the spectral data.

Write up
The write up should conform to a J. Chem. Soc., Perkin Trans. I, style (Title, Abstract, Introduction, Results and Discussion, Experimental, References). Your introduction must include discussion of the following points:
a)The mechanism of the reaction, including a proposal for the initial conversion of palladium (II) to palladium (0).
b)Four recent (1993 or later) examples from the primary literatureof the applications of palladium catalysed reactions. Extra marks for originality and breadth of chemistry!

References and Notes

1.For an excellent general account, see 'Principles and Applications of Organotransition
Metal Chemistry' by J.P. Collman, L.S. Hegedus, J.R. Norton and R.G. Finke,
University Science Books/OUP, 1987.
2.For a comprehensive account of palladium in organic synthesis, including full
experimental details, see 'Palladium Reagents in Organic Synthesis' by R.F. Heck,
Academic Press, 1985.
3.B.M. Trost and T.R. Verhoeven, in 'Comprehensive Organometallic Chemistry', eds
G. Wilkinson, F.G.A. Stone and E.W. Abel, Pergamon Press, 1982, vol. 8, pp. 799-
938.
4.T. Hayashi, M. Konishi and M. Kumada, Tetrahedron Lett., 1979, 1871 5.J.K. Stille, Angew. Chem. Int. Ed. Engl., 1986, 25, 508.
6.N. Miyaura, K. Yamada, H. Suginome and A. Suzuki, J. Am. Chem. Soc., 1985,
107, 972.
7.For this recent example see G. Wu, I. Shimoyama and E.I. Negishi, J. Org. Chem.,
1991, 56, 6506.

Steve Marsden, 22/9/98