Beilstein J. Org. Chem.2013,9, 1296–1310, doi:10.3762/bjoc.9.146
laccase-ABTS follows an electron transfer (ET) mechanism, NHPI, VLA, HBT, and NHAmediators promote a hydrogen atom transfer (HAT) route through the formation of the corresponding N-oxyl radicals as NHDs-Medox species (Scheme 11). The same research group also emphasized the specialization of mediators
morphology and the molecular weight of the starting material [48].
Moreover, this catalytic system could be employed with dioxygen in place of NaClO as the ultimate oxidizing agent [49]. In this case, the mechanism follows a radical chain via classical HAT by PINO abstraction (Scheme 17).
Aldehydes and the
of molecular bromine as a co-catalyst [68] (Scheme 24).
According to the proposed mechanism, Br2 generates ET processes by oxidizing the o-phenanthroline to the corresponding cation radicals. The latter promote in turn ET and HAT processes with NHPI, leading to the formation of PINO.
In 2009 the same
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Graphical Abstract
Scheme 1:
Catalytic role of NHPI in the selective oxidation of organic substrates.
Beilstein J. Org. Chem.2009,5, No. 29, doi:10.3762/bjoc.5.29
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
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Graphical Abstract
Scheme 1:
Synthesis of 4-methoxybiphenyl (4-MeOBP) and by-products in the Kumada reaction.