sealed in a microwave pressure vessel and an overpressure of
dry, oxygen-free, nitrogen (1 bar) introduced. The reagents were
stirred using a magnetic stirrer and heated, using 100 W micro-
wave power, to generate a pressure of 2 bar. This pressure was
maintained for 45 minutes and the resulting solution worked up
as for [Cr(η-C6H5CH3)2]ϩ(BPh4)Ϫ. Yield: 45 % (conventional
heating: 51%). Analysis: C 82.3%, H 6.2% (Calculated for
C36H32BCr: C 82.0%, H 6.1%).
acetonitrile. This was refluxed using microwave irradiation
(40 W) for 30 minutes. Dimethyl maleate (2.30 g) and acetone
(2.4 cm3) were dissolved in acetonitrile (10 cm3) and slowly
added over a period of 30 minutes. The reactants were
heated for a further 3 hours using microwave irradiation (40 W)
before being worked up by the method described in the
literature.25 Yield: 2.25 g (64%, based on dimethyl maleate).
Analysis: C 81.9%, H 6.7% (Calculated for C11H14O4: C 82.2%,
H 6.5%).
Synthesis of n-hexylcyclopropane22
This reaction was performed using the literature procedures
and was based on the following quantities. Oct-1-ene (4.15 g),
diiodomethane (5.09 g), iodine (0.51 g). Although several
methods of preparing a zinc–copper couple were attempted, the
best results were obtained using a commercially available
material (Aldrich, laboratory grade reagent, 3 g). Heating was
effected using 80–100 W applied microwave irradiation for
15 hours. Products were separated by distillation under reduced
pressure. Yield: 52% (conventional heating: 70%). The product
was characterised using IR and NMR spectroscopy. IR cyclo-
References
1 A. G. Whittaker and D.M. P. Mingos, Journal of Microwave Power
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1
propane peaks at 1014, 3001, and 3070 cmϪ1. H NMR (CCl4,
200 MHz): δ 0.10–0.80 (m, 5H, cyclopropyl), 0.85–1.75 (m,
13H).
Synthesis of 2,2’-dinitrobiphenyl (Ullmann reaction)23
This was prepared broadly using the method described by
Fuson and Cleveland.23 o-Iodonitrobenzene (10 g) was melted
under microwave irradiation (80 W) with stirring, and copper
powder (Aldrich, 99.5%, Ϫ325 mesh, 5 g) added over a period
of approximately 20 minutes to reduce the amount of arcing.
The temperature, monitored with a gas pressure thermometer,
was maintained at between 215 and 225 ЊC for 1.5 hours. The
products were worked up as described in the literature. Yield:
65% (conventional heating: 61%). Analysis: C 59.2%, N 11.5%,
H 3.3% (Calculated for C12H8N2O4: C 59.0%, N 11.5%, H
3.3%). mp 122–124 ЊC (literature23 123.5–124.5 ЊC).
11 A. G. Whittaker and D. Mingos, J. Chem. Soc., Dalton Trans., 1992,
2751.
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19 A. G. Whittaker, A Novel Microwave Pressure Vessel, UK Pat.
9910065.3, 1999.
Synthesis of 3,4-dimethylaniline24
4-Nitro-o-xylene (9.0 g) and tin powder (Aldrich, 99.5%, Ϫ100
mesh, 11.25 g) were placed in a reflux apparatus in the micro-
wave oven, and 25 cm3 of concentrated hydrochloric acid slowly
added. Once the vigorous heating had subsided, the reactants
were heated under microwave irradiation (approximately 40 W)
for 60 minutes. The product was then purified using the pro-
cedure described in the literature.24 Yield: 94% (conventional
heating: 97%). Analysis: C 78.4%, N 11.7%, H 9.7% (Calculated
for C8H11N: C 79.3%, N 11.6%, H 9.1%).
20 R. D. Closson, US Pat. 3 115 510, 1963.
21 E. O. Fischer and E. Weiss, Z. Anorg. Allg. Chem., 1956, 286,
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and A. R. E. Tatchel, Practical Organic Chemistry, Prentice Hall,
Englewood Cliffs, NJ, 1989.
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26 S. M. Hannick and Y. K. Kishi, J. Org. Chem., 1983, 48,
3833.
Zinc promoted synthesis of a ꢁ-butyrolactone derivative25
Under a nitrogen atmosphere, zinc powder (Alfa, Ϫ200 mesh,
4.8 g) was stirred in a solution of 2-iodopropane (4.4 cm3) in
3970
J. Chem. Soc., Dalton Trans., 2002, 3967–3970