Modern Heck Reactions - New Trends in Cross-Coupling: Theory and Applications - page 461

intermediate, further undergoing extrusion of N 2 and SO 2 to generate an
arylpalladium species. Oxygen is thus used for palladium-catalysed pre-
oxidation of hydrazide, whereas the arylation itself is more likely to be
realized via an isohypsic Heck pathway.
9.4 Conclusion
The Nobel Prize in Chemistry is awarded for outstanding discoveries,
which change the way in which researchers think and solve problems. The
discovery of Richard Heck of the whole family of transformations taking
place when an organopalladium complex formed from various precursors
adds across a double bond is undoubtedly one of such major break-
throughs. At first looking like yet another example of the emerging
chemistry of transition metal-catalysed reactions, the Heck reaction soon
became a tool (a sharpening stone) for exploring the intricacies and
challenges of transition metal catalysis. Hypotheses on the mechanistic
pathways, principles of catalyst design and operation of catalytic mech-
anisms were put forward, checked, rejected or enforced in the frames of
Heck chemistry and closely related areas and reciprocated in the other
fundamental branches of this science, such as cross-coupling and carbo-
nylation. Heck chemistry has grown enormously to include dozens of
derivative reactions, in addition to the archetypal Mizoroki-Heck reaction.
The diversity, innately present in this basic organometallic transformation
and stemming from various complementary and competing ways of gen-
eration of oranopalladium (and even broader - organometallic, as in
addition to palladium other metals including Rh, Ru, Ni, Co, Fe and
Cuwere noted to be able to take part in Heck-like processes) intermedi-
ates, the involvement of other types of multiple bonds and variable fates
of the carbopalladation adducts account for an overwhelming variety of
derivative processes, and the availability of alternative approaches to the
same synthetic goals (e.g. through the choice of leaving groups, oxidative
or isohypsic reactions). Interestingly and stimulatingly, Heck chemistry is
still full of unanswered questions and unsolved challenges, probably even
of misconceptions awaiting to be resolved. This chapter has attempted to
show the diversity and synthetic might of this brilliant chemistry, al-
though of necessity only a rough cross-section, very far from being
comprehensive.
References
1. M. Oestreich (ed.), The Mizoroki-Heck Reaction, Wiley, Chichester, 2009.
2. R. F. Heck, J. Am. Chem. Soc., 1968, 90, 5538-5542.
3. R. F. Heck, J. Am. Chem. Soc., 1968, 90, 5526-5531.
4. R. F. Heck, J. Am. Chem. Soc., 1968, 90, 5535-5538.
5. R. F. Heck, J. Am. Chem. Soc., 1969, 91, 6707-6714.
6. R. F. Heck, J. Am. Chem. Soc., 1971, 93, 6896-6901.