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Abstract A simple experimental procedure for scaling carbene Brønsted basicity is described. The results highlight the strong basicity of pyrazol‐4‐ylidenes, a type of mesoionic carbene, also named cyclic‐bentallenes (CBA). They are more basic (pKaH>42.7 in acetonitrile) than the popular proazaphosphatrane Verkade bases, and even the Schwesinger phosphazene superbase P4(tBu). The basicity of these compounds can readily be tuned, and they are accessible in multigram quantities. These results open new avenues for carbon centered superbases.
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Moderated Basicity of Endohedral Amine Groups in an Octa‐Cationic Self‐Assembled Cage
Abstract A self‐assembled FeII4L6cage was synthesized with 12 internal amines in the cavity. The cage forms as the dodeca‐ammonium salt, despite the cage carrying an overall 8+ charge at the metal centers, extracting protons from displaced water in the reaction. Despite this, the basicity of the internal amines is lower than their counterparts in free solution. The 12 amines have a sliding scale of basicity, with a ≈6 pKaunit difference between the first and last protons to be removed. This moderation of side‐chain basicity in an active site is a hallmark of enzymatic catalysis.
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- PAR ID:
- 10364097
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 61
- Issue:
- 11
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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