Beilstein J. Org. Chem.2009,5, No. 29, doi:10.3762/bjoc.5.29
of whether or not a pre-wash is used. The induction is therefore most likely to be limited by adsorption of the aryl bromide onto the catalyst surface once catalyst activation is achieved. This is consistent with the Langmuir–Hinshelwood mechanism [17] for surface kinetics which depends on adsorption
become deposited on the catalyst beads on standing between studies and that the initial linear increase in yield was a consequence of the salts being washed off in the continuous flow and adsorption of the organobromide on to the newly freed reactive sites.
It is seen from Figure 6 hat the production of
concentration is necessarily high.
If the rate limiting step in the reaction is the adsorption of the organobromide onto the surface of the catalyst, as we have proposed according to the Langmuir–Hinchelwood mechanism [17], then increasing the flow rate does not give sufficient time for adsorption of the aryl
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Graphical Abstract
Scheme 1:
Synthesis of 4-methoxybiphenyl (4-MeOBP) and by-products in the Kumada reaction.
Beilstein J. Org. Chem.2009,5, No. 19, doi:10.3762/bjoc.5.19
unmodified silica lowered the activity of the catalyst system, presumably via adsorption of some of the Ru(II) catalyst. Under optimal flow conditions, the transfer hydrogenation of acetophenone in isopropanol (using a flow-reactor consisting of a column packed with a slurry of the immobilized catalyst
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Graphical Abstract
Scheme 1:
Enantioselective addition of trimethylsilyl cyanide to benzaldehyde.