Controlling selectivity in N-heterocycle directed borylation of indoles

21Citations
Citations of this article
10Readers
Mendeley users who have this article in their library.

Abstract

Electrophilic borylation of indoles with BX3(X = Cl or Br) using directing groups installed at N1 can proceed at the C2 or the C7 position. The six membered heterocycle directing groups utilised herein, pyridines and pyrimidine, result in indole C2 borylation being the dominant outcome (in the absence of a C2-substituent). In contrast, C7 borylation was achieved using five membered heterocycle directing groups, such as thiazole and benzoxazole. Calculations on the borylation of indole substituted with a five (thiazole) and a six (pyrimidine) membered heterocycle directing group indicated that borylation proceedsviaborenium cations with arenium cation formation having the highest barrier in both cases. The C7 borylated isomer was calculated to be the thermodynamically favoured product with both five and six membered heterocycle directing groups, but for pyrimidine directed indole borylation the C2 product was calculated to be the kinetic product. This is in contrast to thiazole directed indole borylation with BCl3where the C7 borylated isomer is the kinetic product too. Thus, heterocycle ring size is a useful way to control C2vs. C7 selectivity in N-heterocycle directed indole C-H borylation.

Cite

CITATION STYLE

APA

Iqbal, S. A., Yuan, K., Cid, J., Pahl, J., & Ingleson, M. J. (2021). Controlling selectivity in N-heterocycle directed borylation of indoles. Organic and Biomolecular Chemistry, 19(13), 2949–2958. https://doi.org/10.1039/d1ob00018g

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free