More Like this

1. Bioinspired Brønsted Acid-Promoted Regioselective Tryptophan Isoprenylations

   https://doi.org/10.1021/acsomega.1c00515  

   Khopade, Tushar M.; Ajayan, Kalyani; Joshi, Swapnil S.; Lane, Amy L.; Viswanathan, Rajesh (April 2021, ACS Omega)
2. Creating Brønsted acidity at the SiO2-Nb2O5 interface

   https://doi.org/10.1016/j.jcat.2020.10.027  

   Wolek, Andrew T.Y.; Ardagh, M. Alexander; Pham, Hien N.; Alayoglu, Selim; Datye, Abhaya K.; Notestein, Justin M. (February 2021, Journal of Catalysis)
3. Structural considerations for charge‐enhanced Brønsted acid catalysts

   https://doi.org/10.1002/poc.4069  

   Payne, Curtis; Kass, Steven R. (March 2020, Journal of Physical Organic Chemistry)

   Abstract All threeN‐methylated andN‐protonated hydroxypyridinium BAr^F₄^–salt isomers were synthesized and their hydrogen bond donating abilities were investigated. DFT and G4 theory computations along with IR spectroscopic measurements were found to be effective methods for predicting the catalytic activities of these O–H and N–H Brønsted acids. A UV‐vis titration approach for rapidly quantifying hydrogen bond donating ability revealed that carbon‐hydrogen bonds also can participate in electrostatic interactions, but the presence of multiple equilibrium complexes results in a limitation of this method. In the methylated series of hydroxypyridines, the ortho and para isomers displayed modest rate enhancements relative to the meta derivative. Protonation introduces a new acidic site and the ortho hydroxypyridinium ion salt is a significantly more active catalyst than all of the other species examined. This is indicative of bidentate activation by the N–H and O–H acidic sites, and suggests a new design strategy for improving charge‐enhanced catalysts. 

   more » « less
4. Brønsted-acid-mediated cyclocondensation towards dihydro-1-benzazepines

   https://doi.org/10.1016/j.tetlet.2025.155572  

   Xu, Letian; Vasquez, Alena M; Medina, Jose M; Sun, Juntao; Engle, Keary M (May 2025, Tetrahedron Letters)
5. Chiral Brønsted acid-controlled intermolecular asymmetric [2 + 2] photocycloadditions

   https://doi.org/10.1038/s41467-021-25878-9  

   Sherbrook, Evan M.; Genzink, Matthew J.; Park, Bohyun; Guzei, Ilia A.; Baik, Mu-Hyun; Yoon, Tehshik P. (September 2021, Nature Communications)

   Abstract Control over the stereochemistry of excited-state photoreactions remains a significant challenge in organic synthesis. Recently, it has become recognized that the photophysical properties of simple organic substrates can be altered upon coordination to Lewis acid catalysts, and that these changes can be exploited in the design of highly enantioselective catalytic photoreactions. Chromophore activation strategies, wherein simple organic substrates are activated towards photoexcitation upon binding to a Lewis acid catalyst, rank among the most successful asymmetric photoreactions. Herein, we show that chiral Brønsted acids can also catalyze asymmetric excited-state photoreactions by chromophore activation. This principle is demonstrated in the context of a highly enantio- and diastereoselective [2+2] photocycloaddition catalyzed by a chiral phosphoramide organocatalyst. Notably, the cyclobutane products arising from this method feature atrans-cisstereochemistry that is complementary to other enantioselective catalytic [2+2] photocycloadditions reported to date. 

   more » « less