Advanced Synthesis & Catalysis
10.1002/adsc.201901446
General procedure for the synthesis of α-
In light of our observations, we propose the
trifluoromethylacrylic acids (3).
following catalytic cycle (Scheme 5). After an
oxidative addition, the complex A reacted with silver
carboxylate 11 to give the neutral complex B. The
silver plays an important role as halide abstracter
To a vial (2 mL) were added 2-(trifluoromethyl)acrylic
acid 1 (0.3 mmol, 1.5 equiv), iodoarene 2 (0.2 mmol, 1.0
2 3 2
equiv), Ag CO (0.22 mmol, 1.1 equiv), Pd(TFA) (0.01
during this step.[
7],[21]
mmol, 5 mol%), and 1,4-dioxane (0.5 mL, 0.4 M of
iodoarene). The vial was then sealed. The reaction mixture
was stirred at 90 or 110 °C for 1 hour and was then cooled
to room temperature. The resulted reaction mixture was
purified directly by silica gel column chromatography
Then an insertion of the aryl
group in the double bond furnishs the complex C.
From C, β-H elimination, a syn-process, can proceed
either towards the formation of Z or E-compound,
taking into account that neither intermediate C’ or C’’
seems more stable than the other one because of
steric hindrance in both cases. Finally, the complex D
is formed by β-H elimination, and reductive
elimination ends the catalytic cycle to give the
desired acid 3 and regenerated catalyst.
(
2 2
TLC: CH Cl /MeOH (AcOH), 20/1 (1%)).
Acknowledgements
This work was partially supported by INSA Rouen, Rouen
University, CNRS, EFRD, Labex SynOrg (ANR-11-LABX- 0029),
and Rꢀgion Haute-Normandie (Crunch Network). P.X. thanks the
CSC (China Scholarship Council) for a doctoral fellowship. The
authors thank Dr. D. Harakat (Reims University) for HRMS
analyses, and Dr. K. Plé (Orléans University) for polishing
english.
To summarize, we have developed a new relevant
access to α-CF -acrylic acids, scarcely studied in the
3
literature despite their great potential. The ligand-free
Mizoroki-Heck reaction gave good to excellent yields
of fluorinated acrylic acids and tolerated the presence
of many organic functional groups. Nevertheless, the
stereoselectivity of the reaction was quite low and the
various attempts to increase it were unsuccessful to
date. Based on further experiments, a hypothetic
catalytic cycle involving a silver carboxylate salt as a
key intermediate was proposed. This mechanism also
gave an explanation as to the observed stereo-
selectivity. We also demonstrated the high versatility
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Experimental Section
5
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