p<i>K</i>_a Values of Chiral Brønsted Acid Catalysts: Phosphoric Acids/Amides, Sulfonyl/Sulfuryl Imides, and Perfluorinated TADDOLs (TEFDDOLs)

Abstract

Measure what is measurable, and make measurable what is not so! This timeless quotation by Galileo forms the basis of all quantitative understanding, including asymmetric organocatalysis. We report pKa values for 15 chiral Brønsted acid catalysts in DMSO solutions (see scheme): the strongest acids were bis-sulfonyl/sulfuryl imides (pKa=1.7–1.9) followed by phosphoric acids/amides (pKa=2.4–4.2). A new class of chiral Brønsted acids, tetrakis-perfluoroalkyl analogues of TADDOLs (TEFDDOLs) have pKas from 2.4 to 5.7. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.