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Theoretical investigation on the Cu( i )-catalyzed N -carboxamidation of indoles with isocyanates to form indole-1-carboxamides: effects of solvents
Ist Teil von
New journal of chemistry, 2020-06, Vol.44 (23), p.9878-9887
Ort / Verlag
Cambridge: Royal Society of Chemistry
Erscheinungsjahr
2020
Link zum Volltext
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
The mechanisms of Cu(
i
)-catalyzed
N
-carboxamidation of indoles with isocyanates are studied in detail to explore the effects of DMSO
vs.
THF
vs.
acetone based on theoretical calculations. The calculated results are shown as follows: (a) the Cu(
i
) catalyst can activate the N1–C1 double bond of
im1
to promote the intermolecular addition. (b) The solvents DMSO, THF and acetone can not only act as the hydrogen-bond acceptor to facilitate intermolecular addition between C1 and N2 by the hydrogen-bond N2–H1⋯O2 (O3 or O4), but also play the role of a proton-transfer shuttle in assisting the H1
+
-shift by the stepwise proton-transport process (the protonation of solvent and the deprotonation of solvent-H
+
). Due to the assistance of DMSO, THF and acetone, the rate-determining free energy barrier of the Cu(
i
)-catalyzed reaction is greatly reduced from 44.7 to 24.3, 25.6 and 28.6 kcal mol
−1
, which explains the experimental phenomena well (95%
vs.
58%
vs.
24% in yields). More importantly, the electron-donating ability of solvents (DMSO, THF and acetone) is found to be the primary factor that critically affects the catalytic activity of solvents, and the stronger electron-donating properties of solvents (DMSO > THF > acetone) are favorable for the present Cu(
i
)-catalyzed reactions. (c) Substrate
1a
can also assist the reaction, but the catalytic capability of
1a
is weaker than that of solvents DMSO, THF and acetone (energy barrier: 40.0
vs.
24.3, 25.6 and 28.6 kcal mol
−1
). Briefly, the present study is expected to help one understand the influence of solvents on the transition metal-catalyzed reactions including the addition reaction and the proton-transfer process.