MICROWAVE-ENHANCED DEUTERIATION/TRITIATION STUDIES

J. R. Jones and S. Y. Lu

Department of Chemistry, School of Physics and Chemistry, University of Surrey, Guildford, Surrey, GU2 7XH UK
E-mail: http://www.mdpi.net/ecsoc-5/e0039/[email protected] and http://www.mdpi.net/ecsoc-5/e0039/[email protected]

Received: 15 August 2001 / Uploaded 22 August 2001

Introduction

Deuterium (²H) and tritium (³H) labelled compounds continue to play important roles in the physical and life sciences. More efficient and selective preparation methods are required to keep pace with the increasing demand from academics and industrialists for such labelled compounds, and to address legislative and environmental issues such as tighter control of the amount of radioactivity released to the atmosphere, the cost associated with the storage and disposal of radioactive waste etc. There are well-established methods for preparing deuterium/tritium labelled compounds (Table 1). Deuteriation studies often act as a useful stepping stone for the development of tritiation procedures. The tritiations are usually performed on a smaller (e.g. mg rather than g) scale and more attention has to be paid to the radioactive waste produced.

Table 1 Widely used deuteriation/tritiation procedures

Many of the important developments that have taken place in catalysis over the last 20 years have benefited the radiosynthesis area and of these energy-enhanced procedures, and specifically microwave dielectric heating (2.45 GHz) offers the greatest potential.^1-5 The application of microwaves to radiochemistry has made the development of faster, cleaner, more selective procedures possible.
 
 

Results

Our efforts have covered a wide range of reactions (Table 2), including hydrogenations, borohydride reductions, aromatic dehalogenations, decarboxylations and hydrogen isotope exchange reactions.
 

Table 2 Microwave-enhanced deuteriation/tritiation procedures

 

Highlights of the studies are listed below. Reactions were performed in domestic microwave ovens.
 

Solid state sodium borohydride/borodeuteride reductions

(For the table of the results, see the pdf file)

Acid and metal-catalysed deuteriation of heterocyclic compounds
(For the table of the results, see the pdf file)

Aromatic decarboxylations

Catalytic dehalogenations using solid deuterium/tritium donors
 

Conclusion

The important point to emerge from these studies is that in addition to marked accelerations in reaction rates microwaves provide new routes e.g. where the use of solvents can be avoided, where forming the salts is adventitious, etc. This new approach to radiosynthesis, which we have illustrated by reference to deuterium and tritium, may also be of benefit in other radiosynthetic areas e.g. halogenation reactions.
 
 

References

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2. P. Lidstrom, J. Tierney, B. Wathey and J. Westman, in the conference proceedings of Transforming medicinal chemistry, Cambridge, 12-14 April, 2000.
3. R. S. Varma, Green Chem., 1999, 43.
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6. M. H. Al-Qahtani, N. Cleator, T. N. Danks, R. N. Garman, J. R. Jones, S. Stefaniak, A. D. Morgan and A. J. Simmonds, J. Chem. Res.(S), 1998, 400.
7. J. M. Barthez, A. V. Filikov, L. B. Frederiksen, M. L. Huguet, J. R. Jones and S. Y. Lu, Can. J. Chem., 1998, 76, 726.
8. W. Th. Erb, J. R. Jones and S. Y. Lu, J. Chem. Res(S), 1999, 728.
9. S. Anto, G. Getvoldsen, J. R. Harding, J. R. Jones, S. Y. Lu and J. C. Russell, J. Chem. Soc. Perkin Trans 2, 2000, 2208.
10. L. B. Frederiksen, T. H. Grobosch, J. R. Jones, S. Y. Lu and C. C. Zhao, J. Chem. Res(S), 2000, 42.
11. J. R. Jones, W. J. S. Lockley, S. Y. Lu and S. P. Thompson, Tetrahedron Lett., 2001, 42, 331.
12. J. R. Jones and S. Y. Lu, unpublished results.