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doi.org/10.1002/chem.202100075
Chemistry—A European Journal
ployed 4’-methylchalcone (1d) and 4’-chlorochalcone (1e)
were obtained in good yield. trans-Benzalacetone (1 f) and 2-
cyclohexenone (1g) afforded the corresponding vicinal allylary-
lation products in a selective manner. One could argue that
these transformations could be achieved with the same start-
ing materials using a stepwise approach based on a hydroary-
lation to give a ketone followed by an allylation of the inde-
pendently prepared enolate from the ketone. However, it
would be difficult to prepare the corresponding enolates from
the hydroarylation products, that is, ketones, in a regioselective
manner since the a-protons are thermodynamically and kineti-
cally indistinguishable.[15] The allylarylation of cyclic alkene 1g
proceeded in a highly diastereoselective manner to afford the
trans-isomer as the major product. In contrast, the use of acy-
clic alkenes afforded the corresponding products as a mixture
of diastereomers. As expected, the present conditions could be
applied to the highly electron-deficient alkene 1h to furnish
the desired product in almost quantitative yield. Terminal
enone 1i gave the product in 10% yield. Other alkenes includ-
ing enoates, vinyl sulfone, acrylonitrile, and trans-b-nitrostyrene
were not viable under the present conditions.[16] Electron-defi-
cient alkyne 12 afforded the corresponding allylarylated prod-
uct 13 in moderate yield in the presence of Pd(OAc)2/P(m-tol)3
and a PBn(tBu)2-derived cyclometallated complex 7d as a cata-
lyst [Eq. (8)]. Aryl boronates with electron-rich, electron-poor,
and sterically demanding aryl groups (2b–d) are tolerated
under the present conditions. Aryl boronates 2e and 2 f bear-
ing primary alkyl tosylate and bromide, which would not work
well under organocuprate conditions, afforded the correspond-
ing products in good yield, whereas an aryl boronate with a
free hydroxy group was not applicable.[16] Regarding the scope
of the reaction with respect to allylic carbonates, 2-methylallyl
methyl carbonate (3b) and cinnamyl methyl carbonate (3c), in
addition to 3a, afforded the corresponding products in good
to high yield. In terms of the scope of alkenes, the present
conditions are superior to those based on the cooperative Pd/
Cu catalysis.[9b] For example, 1a, 1 f, and 1g did not afford the
allylarylated products under the conditions based on coopera-
tive Pd/Cu catalysis as they are shown in parentheses in
Scheme 2.
mained constant during the reaction due to the mild condi-
tions.
Conclusions
In conclusion, we have developed a system for the allylaryla-
tion of electron-deficient alkenes based on merging Pd0/PdII
redox and PdII/PdII non-redox catalytic cycles. The method af-
fords a variety of carbon skeletons from readily available and
bench-stable starting materials. This report demonstrates that
a combination of cyclometallated and non-cyclometallated
complexes, which are responsible for PdII/PdII non-redox and
Pd0/PdII redox manifolds, can serve as a powerful tool for
future development of cooperative transition-metal catalysis.
Further applications of this unique Pd-based cooperative cata-
lytic system are currently in progress in our laboratory.
Acknowledgements
This study was supported by JSPS KAKENHI Grant Numbers
JP17KT0098, JP18K14213, JP20H04814 (“Hybrid Catalysis”), and
JST, CREST Grant Number JPMJCR14L3 (“Establishment of Mo-
lecular Technology towards the Creation of New Functions”).
Conflict of interest
The authors declare no conflict of interest.
Keywords: allylation · cooperative catalysis · metallacycles ·
Michael addition · palladium
erative Catalysis: Designing Efficient Catalysts for Synthesis (Ed.: R.
Peters), Wiley-VCH: Weinheim, 2015; c) Science of Synthesis: Dual Cataly-
sis in Organic Synthesis 1, (Ed.: G. A. Molander), Thieme, Stuttgart, 2019.
[2] For selected references on cooperative transition-metal catalysis see
the following entries. For Pd/Cu catalysis, see: a) K. Sonogashira, Y.
Gooßen, G. Deng, L. M. Levy, Science 2006, 313, 662–664; d) J. Huang,
J. Chan, Y. Chen, C. J. Borths, K. D. Baucom, R. D. Larsen, M. M. Faul, J.
Finally, the preliminary asymmetric allylarylation of 1a with
2a and 3b was conducted using the chiral bidentate ligand
(R,R,R)-(+)-Ph-SKP,[17] which furnished 4o in 75% yield with
42% enantiomeric excess [Eq. (9)]. The enantioselectivity re-
Chem. Eur. J. 2021, 27, 5035 –5040
5039
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