104174-39-2Relevant academic research and scientific papers
Asymmetric Oxidative Coupling of Phenols and Hydroxycarbazoles
Kang, Houng,Lee, Young Eun,Reddy, Peddiahgari Vasu Govardhana,Dey, Sangeeta,Allen, Scott E.,Niederer, Kyle A.,Sung, Paul,Hewitt, Kirsten,Torruellas, Carilyn,Herling, Madison R.,Kozlowski, Marisa C.
, p. 5505 - 5508 (2017)
The first examples of asymmetric oxidative coupling of simple phenols and 2-hydroxycarbazoles are outlined. Generation of a more vanadium catalyst by ligand design and by addition of an exogenous Br?nsted or Lewis acid was found to be key to coupling the more oxidatively resistant phenols. The resultant vanadium complex is both more Lewis acidic and more strongly oxidizing. Good to excellent levels of enantioselectivity could be obtained, and simple trituration readily provided the products with ≥95% ee.
Enantioselective Vanadium-Catalyzed Oxidative Coupling: Development and Mechanistic Insights
Kang, Houng,Herling, Madison R.,Niederer, Kyle A.,Lee, Young Eun,Vasu Govardhana Reddy, Peddiahgari,Dey, Sangeeta,Allen, Scott E.,Sung, Paul,Hewitt, Kirsten,Torruellas, Carilyn,Kim, Gina J.,Kozlowski, Marisa C.
, p. 14362 - 14384 (2018/11/23)
The evolution of a more reactive chiral vanadium catalyst for enantioselective oxidative coupling of phenols is reported, ultimately resulting in a simple monomeric vanadium species combined with a Br?nsted or Lewis acid additive. The resultant vanadium complex is found to effect the asymmetric oxidative ortho-ortho coupling of simple phenols and 2-hydroxycarbazoles with good to excellent levels of enantioselectivity. Experimental and quantum mechanical studies of the mechanism indicate that the additives aggregate the vanadium monomers. In addition, a singlet to triplet crossover is implicated prior to carbon-carbon bond formation. The two lowest energy diastereomeric transition states leading to the enantiomeric products differ substantially with the path to the minor enantiomer involving greater torsional strain between the two phenol moieties.
