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. 2020 Jul 20;59(30):12527-12533.
doi: 10.1002/anie.202003029. Epub 2020 May 11.

Predicting Absolute Rate Constants for Huisgen Reactions of Unsaturated Iminium Ions with Diazoalkanes

Jingjing Zhang  1 , Quan Chen  2 , Robert J Mayer  2 , Jin-Dong Yang  1 , Armin R Ofial  2 , Jin-Pei Cheng  1   3 , Herbert Mayr  2
Affiliations

Predicting Absolute Rate Constants for Huisgen Reactions of Unsaturated Iminium Ions with Diazoalkanes

Jingjing Zhang et al. Angew Chem Int Ed Engl. .

Abstract

The kinetics and stereochemistry of the reactions of iminium ions derived from cinnamaldehydes and MacMillan's imidazolidinones with diphenyldiazomethane and aryldiazomethanes were investigated experimentally and with DFT calculations. The reactions of diphenyldiazomethane with iminium ions derived from MacMillan's second-generation catalysts gave 3-aryl-2,2-diphenylcyclopropanecarbaldehydes with yields >90 % and enantiomeric ratios of ≥90:10. Predominantly 2:1 products were obtained from the corresponding reactions with monoaryldiazomethanes. The measured rate constants are in good agreement with the rate constants derived from the one-center nucleophilicity parameters N and sN of diazomethanes and the one-center electrophilicity parameters E of iminium ions as well as with quantum chemically calculated activation energies.

Keywords: diazoalkanes; electrophiles; kinetics; nucleophiles; organocatalysis.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Iminium hexafluorophosphates used in this work (with electrophilicities E from ref. 12).
Figure 1
Figure 1
Single‐crystal X‐ray structure of 5 c (ellipsoids are shown at the 20 % probability level).
Scheme 2
Scheme 2
Reaction of 1 a with phenyldiazomethane (6 a).
Figure 2
Figure 2
Single‐crystal X‐ray structure of the potassium cyclopropanecarboxylate 9 obtained by oxidation of 7 b (K+ counterion omitted for clarity; thermal ellipsoids are shown at the 50 % probability level).
Scheme 3
Scheme 3
Reactions of iminium hexafluorophosphates 1 with (4‐cyanophenyl)diazomethane 6 b.
Figure 3
Figure 3
Monoexponential time‐dependent decay of the absorbance (Abs, at 400 nm) for the reaction of 2 a (2.87×10−5  m) with 4 (3.53×10−3  m) in dichloromethane at 20 °C. Inset: Correlation of k obs (s−1) with the concentrations of 4.
Figure 4
Figure 4
Gibbs energy profile for the reaction of the iminium ion 1 a with diphenyldiazomethane (4) at the (SMD=DCM)//B3LYP‐D3(BJ)/def2‐SVP level of theory.
Figure 5
Figure 5
Gibbs energy profile for the reactions of iminium ion 1 a (a) and of iminium ion D (b) with phenyldiazomethane (6 a) at the (SMD=DCM)//B3LYP‐D3(BJ)/def2‐SVP level of theory.
See this image and copyright information in PMC

References

    1. None
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