Dehalogenation microwave-enhanced

It is interesting to remark that classical hydrogenation is a method used to prepare deuterium-labeled compounds by aromatic dehalogenation, but the usual reaction conditions suffer from several limitations. A microwave-enhanced catalytic dehalogenation procedure for rapid and specific deuterium labeling of N-4-picolyl-4-halogenobenzamide 68, by use of deuterated formate, [41] was recently reported (Scheme 8.25). 

Jones, J.R., Lockley, W.J.S., Lu, S.Y. and Thompson, S.P, Microwave-enhanced aromatic dehalogenation studies a rapid deuterium-labelling procedure,Tetrahedron Lett., 2001, 42, 331-332. 

In our own preliminary studies [101] on parallel procedures under microwave-enhanced conditions, we have used the Radley s RDT 24 place PTFE carousel reaction station on the turntable of the Matsui M 169BT microwave oven. In this way, we have studied the catalytic activity of RhCh and Pd(OAc)2 towards the reduction or dehalogenation of 4-bromocinnamic acid and structurally similar compounds. A nine-reaction matrix was used under microwave-enhanced conditions as illustrated in Scheme 18.12 - greatly reduced reaction times and easy optimization of reaction conditions are immediate benefits. As robotics come to play an increasingly important role in chemistry, one can immediately see more sophisticated labeling experiments being undertaken. 

Silica- or alumina-supported Pd-Fe mono- or bimetallic dehalogenation catalysts were prepared by conventional and microwave-assisted calcination. The catalysts synthesised under microwave conditions gave a higher conversion in the dechlorination of chlorobenzene. The effects were attributed to an enhanced crystallite size, a lower susceptibility to alloy formation and differences in the Pd morphology73,74. 

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