The Dynamic Covalent Chemistry of Amidoboronates: Tuning the rac₅/rac₆ Ratio via the B−N and B−O Dynamic Covalent Bonds

Abstract

Invited for this month's cover is the group of Anna J. McConnell and Christian Näther from Christian‐Albrechts‐Universität zu Kiel, Germany. The cover picture shows an amidoboronate puzzle divided into four quarters that represent four possible amidoboronates. How do these amidoboronates interconvert? The right combination of aniline (yellow circles) and catechol (grey and purple circles) pieces solves this conundrum and the amidoboronates interconvert via dynamic covalent B‐N (left to right) and B‐O bonds (top to bottom). More information can be found in the Research Article by Anna J. McConnell and co‐workers.

Amidoboronates: bringing together the synthesis of BN-heterocyclesviaa reductive coupling and dynamic covalent chemistry

“…Thus, we investigated the reductive coupling of N -aryl iminoboronates using reductants such as cobaltocene and decamethylcobaltocene, initially focusing on two series of iminoboronates ( 1 and 2 ) where the para -substituent of the aniline and the catechol were varied to investigate electronic effects (Scheme 5). 70,71…”

“…2c). 70,71 For 4c , crystal structures of three polymorphs of the cobaltocenium salt were obtained in addition to one crystal structure of the decamethylcobaltocenium salt. The X-ray crystal structures of the meso 5 and rac 5 isomers confirmed dimerisation via C–C bond formation between the two five-membered rings and Fig.…”

“…4). 71 For the pyrocatechol series, rac 6 -3a,c–d and rac 5 -3e crystallised from the reductive couplings. While rac 6 -3a did not interconvert to the rac 5 isomer, the amount of the rac 5 isomer for the other derivatives increased with more electron-donating substituents (Scheme 11a, Fig.…”

“…22 Therefore, the dynamic covalent nature of the B–O bonds of amidoboronates was explored in catechol exchange experiments. 71…”