10.1002/cctc.202001175
ChemCatChem
FULL PAPER
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typically furnishes the respective carbonates, a Lewis base
catalyst is pivotal to switch chemoselectivity in favor for C-Cl and
C-Br bond formation. Indeed, 1-formylpyrrolidine (FPyr) and
diethylcyclopropenone (DEC) were identified as potent catalysts,
which is evidenced by turn-over numbers up to 40. Remarkably,
primary, secondary and even tertiary substrates are suitable
regardless if they are benzylic, allylic or aliphatic.
As an important aspect, acid labile functions like tert-
butylesters, acetals and silylethers are compatible. This is
reasoned by the emergence of neutral phenol and CO2 as by-
products instead of strongly acidic HCl like in the case of
chlorinations exploiting phosgene (COCl2) and thionyl chloride
(SOCl2). The isolation of phenol attested that a recycling using
phosgene, which is the cheapest reagent for the activation of OH
groups, would be reasonable in a technical scale. In addition,
these nucleophilic substitutions proceed under stereochemical
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a
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Acknowledgements
We want to thank the German research foundation (DFG) and the
Fonds of the Chemical Industry (Liebig fellowship for P. H. H. and
PhD fellowship for T. S.) for generous support. In addition, we
would like to thank Rudolf Thomes for measuring HR-MS.
portal/themenspektrum/gefahrstoffe/ghs/inhalt-von-ghs/kennzeichnung/
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Keywords: organocatalysis • nucleophilic substitutions •
phosgene substitutes • stereochemical inversion • homogenous
catalysis
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