Wiskur S L, Lavigne J J, Ait-Haddou H, Lynch V, Chiu Y H, Canary J W, Anslyn E V
Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, USA.
Org Lett. 2001 May 3;3(9):1311-4. doi: 10.1021/ol0156805.
[structure in text] The pK(a) values and the geometries of secondary and tertiary amines adjacent to boronic acids were determined using potentiometric and (11)B NMR titrations. The studies showed that the secondary ammonium ion has a pK(a) similar to that of the tertiary ammonium species, which leads to the formation of tetrahedral boron centers at pH values above approximately 5.5. Therefore, secondary amines as well as tertiary amines, when placed proximal to boron centers, can be used to create tetrahedral boronic acids at neutral pH for diol complexation.
