2593-53-5Relevant academic research and scientific papers
Symmetry in Cascade Chirality-Transfer Processes: A Catalytic Atroposelective Direct Arylation Approach to BINOL Derivatives
Wang, Jin-Zheng,Zhou, Jin,Xu, Chang,Sun, Hongbin,Kürti, László,Xu, Qing-Long
, p. 5202 - 5205 (2016)
Herein we disclose a scalable organocatalytic direct arylation approach for the regio- and atroposelective synthesis of non-C2-symmetric 2,2′-dihydroxy-1,1′-binaphthalenes (BINOLs). In the presence of catalytic amounts of axially chiral phosphoric acids, phenols and naphthols are coupled with iminoquinones via a cascade process that involves sequential aminal formation, sigmatropic rearrangement, and rearomatization to afford enantiomerically enriched BINOL derivatives in good to excellent yields. Our studies suggest that the (local) symmetry of the initially formed aminal intermediate has a dramatic impact on the level of enantioinduction in the final product. Aminals with a plane of symmetry give rise to BINOL derivatives with significantly lower enantiomeric excess than unsymmetrical ones featuring a stereogenic center. Presumably asymmetric induction in the sigmatropic rearrangement step is significantly more challenging than during aminal formation. Sigmatropic rearrangement of the enantiomerically enriched aminal and subsequent rearomatization transfers the central chirality into axial chirality with high fidelity.
The Diels-Alder reactions of para-benzoquinone nitrogen-derivatives: An experimental and theoretical study
Uliana, Marciana P.,Servilha, Bruno M.,Alexopoulos, Olga,De Oliveira, Kleber T.,Tormena, Cláudio F.,Ferreira, Marco A.B.,Brocksom, Timothy J.
, p. 6963 - 6973 (2015/11/09)
An experimental and theoretical study of the comparative reactivity and selectivity of the Diels-Alder reactions of para-benzoquinones and three nitrogen derivatives have been performed. The mono-oximes derivatives do not react under the tested reaction conditions, whereas the tosylated mono-oximes react slowly. However, the mono N-tosyl imines show excellent reactivity, and superior to the parent parabenzoquinones. DFT calculations support these experimental results.
Synthesis and antidepressant evaluation of three para-benzoquinone mono-oximes and their oxy derivatives
De Sousa, Damiao Pergentino,Schefer, Renata Rabelo,Brocksom, Ursula,Brocksom, Timothy John
, p. 148 - 155 (2007/10/03)
A series of three para-benzoquinone mono-oximes and four oxy-derivatives were prepared and tested for their antidepressant properties. The (4E) oxime of 2-isopropyl-5-methyl-para-benzoquinone (4) and the corresponding 2-diethylamino-ethyl derivative (10)
Catalytic Autoxidation of Benzoquinone Dioximes with Nitrogen Oxides: Steric Effects on the Preparation of Monomeric Dinitrosobenzenes
Rathore, R.,Kim, J. S.,Kochi, J. K.
, p. 2675 - 2684 (2007/10/02)
A convenient catalytic method for the autoxidation of quinone dioximes to dinitrosobenzenes with dioxygen is based on the presence of small amounts of nitrogen oxides.The catalytic cycle is deduced from the facile chemical oxidation of quinone dioxime to dinitrobenzene with stoichiometric amounts of the 1-electron oxidant, nitrosonium-either as the NO+BF4- salt or the disproportionated ion pair NO+NO3- derived from nitrogen dioxide.The regeneration of NO+ occurs by the subsequent oxidation of nitric oxide (NO) with dioxygen to nitrogen dioxide followed by the disproportionation to nitrosonium nitrate in the presence of electron-rich donors.Indeed, dioximes of various p-benzoquinones are shown to be strong reducing agents by transient electrochemistry.Electrochemical oxidation also leads to dinitrosobenzenes in good yields at anodic potentials of ca. 1.3 V.The substitution of p-dinitrosobenzene with bulky alkyl groups stabilizes the monomeric form, which is otherwise extensively associated.
