1095-03-0Relevant articles and documents
Young,Anderson
, p. 1805,1807 (1962)
Mild metal-free syn-stereoselective ring opening of activated epoxides and aziridines with aryl borates
Pineschi, Mauro,Bertolini, Ferruccio,Haak, Robert M.,Crotti, Paolo,Macchia, Franco
, p. 1426 - 1428 (2005)
A conceptually new, simple and practical method for the syn-nucleophilic displacement of aryl and vinyl epoxides and aryl aziridines with (substituted) phenols, using aryl borates as activating nucleophiles under neutral conditions, is reported. The Royal Society of Chemistry 2005.
The Nature of meso - And pyro -Borate Precatalysts to the VANOL and VAPOL BOROX Catalysts
Zhao, Wenjun,Yin, Xiaopeng,Gupta, Anil K.,Zhang, Xin,Wulff, William D.
, p. 1606 - 1614 (2015)
The structures of the meso- and pyro-borate esters generated by treatment of the VANOL and VAPOL ligands with triphenylborate have been revisited. These species were previously identified as precatalysts that could be in situ converted into VANOL and VAPOL BOROX catalysts by an imine substrate. The complete assignment of all protons for both the meso- and pyro-borate esters of both ligands was aided by the 1H NMR spectrum of each generated from pentadeuterophenol. There were significant differences between the chemical shifts for certain protons in the meso- and pyro-borate species in both the VANOL and VAPOL derivatives. Optimized structures for the meso-borates and two different isomers of the pyro-borates were determined by DFT calculations for each ligand. For each ligand the cyclic pyro-borate was found to be lower in energy than the corresponding linear pyro-borate at the B3LYP/6-311+G(d,p) level of theory. The structures of the cyclic pyro-borate esters were more consistent with the observed 1H NMR chemical shifts than the linear pyro-borates for each ligand and thus the structures of the pyro-borates esters of VANOL and VAPOL have been re-assigned as the cyclic isomers.
Lalancette
, p. 2356 (1964)
Pyro-Borates, Spiro-Borates, and Boroxinates of BINOL - Assembly, Structures, and Reactivity
Hu, Gang,Gupta, Anil K.,Huang, Li,Zhao, Wenjun,Yin, Xiaopeng,Osminski, Wynter E. G.,Huang, Rui H.,Wulff, William D.,Izzo, Joseph A.,Vetticatt, Mathew J.
supporting information, p. 10267 - 10285 (2017/08/09)
VANOL and VAPOL ligands are known to react with three equivalents of B(OPh)3 to form a catalytic species that contains a boroxinate core with three boron atoms, and these have proven to be effective catalysts for a number of reactions. However, it was not known whether the closely related BINOL ligand will likewise form a boroxinate species. It had simply been observed that mixtures of BINOL and B(OPh)3 were very poor catalysts compared to the same mixtures with VANOL or VAPOL. Borate esters of BINOL have been investigated as chiral catalysts, and these include meso-borates, spiro-borates, and diborabicyclo-borate esters. Borate esters are often in equilibrium, and their structures can be determined by stoichiometry and/or thermodynamics, especially in the presence of a base. The present study examines the structures of borate esters of BINOL that are produced with different stoichiometric combinations of BINOL with B(OPh)3 in the presence and absence of a base. Depending on conditions, pyro-borates, spiro-borates, and boroxinate species can be generated and their effectiveness in a catalytic asymmetric aziridination was evaluated. The finding is that BINOL borate species are not necessarily inferior catalysts to those of VANOL and VAPOL but that, under the conditions, BINOL forms two different catalytic species (a boroxinate and a spiro-borate) that give opposite asymmetric inductions. However, many BINOL derivatives with substitutents in the 3- and 3′-positions gave only the boroxinate species and the 3,3′-Ph2BINOL ligand gave a boroxinate catalyst that gives excellent inductions in the aziridination reaction. BINOL derivatives with larger groups in the 3,3′-position will not form either spiro-borates or boroxinate species and thus are not effective catalysts at all.
Substrate-induced covalent assembly of a chemzyme and crystallographic characterization of a chemzyme-substrate complex
Hu, Gang,Gupta, Anil K.,Huang, Rui H.,Mukherjee, Munmun,Wulff, William D.
supporting information; experimental part, p. 14669 - 14675 (2010/12/25)
A substrate induced covalent assembly of a highly organized chemzyme known to be effective in both catalytic asymmetric aziridination and aza Diels-Alder reactions is described and the information gained from which led to an efficient one-pot aziridination protocol. The crystal structures of two chemzyme-iminium complexes were elucidated by X-ray diffraction analysis that provides critical insights into the binding of the substrates with the chemzyme.
