On repeating pivaloyl directed indole borylation in dichloromethane (DCM) with BBr3 (1 m in heptanes or hexanes), the formation of small quantity of precipitate was observed in a number of cases at the 5 x-BBr2/6 x-BBr2 stage. Previously the authors of this Communication had reported the C2:C7 borylation ratio (at the BBr2 stage) based on in situ solution 1H NMR spectroscopy (in DCM/hexanes (or heptanes) mixes), thus they reassessed all of these ratios using a different procedure. Specifically, borylation was performed in DCM using 1 m BBr3 in DCM using otherwise identical conditions to those we previously reported. This led to homogenous solutions in most cases, and where solid was observed the sample was diluted with DCM until it was homogenous and then analysed. This led in three cases to different ratios to that originally reported (due to the different solubility of 5 x-BBr2 vs 6 x-BBr2), thus three ratios in the table on page 31 of the Supporting Information should be corrected to those below. The 5 k-BBr2/6 k-BBr2 ratio was checked further by performing the borylation as previously described (in DCM with 1 m BBr3 in heptanes), reducing the sample to dryness in vacuo and dissolving a portion of the resultant solid in DCM for analysis by NMR spectroscopy. 6-fluoro (starting compound 2 d) + BBr3 → C7-BBr2:C2-BBr2 ratio = 90:10 6-chloro (starting compound 2 k) + BBr3 → C7-BBr2:C2-BBr2 ratio = 91:9 6–bromo (starting compound 2 l) + BBr3 → C7-BBr2:C2-BBr2 ratio = 86:14 Thus the brief discussion on the isomerisation of 5 k-BBr2/6 k-BBr2 during pinacol installation is not warranted. The authors apologise for this error. All other statements in the manuscript remain valid.
|Number of pages||1|
|Journal||Angewandte Chemie - International Edition|
|Publication status||Published - 16 Mar 2021|
- directing groups
- electrophilic aromatic substitution
ASJC Scopus subject areas