131759-35-8Relevant academic research and scientific papers
Chiral Molecular Propellers of Triarylborane Ammonia Adducts
Kemper, Michael,Engelage, Elric,Merten, Christian
supporting information, p. 2958 - 2962 (2020/12/15)
Chiral molecular propeller conformations have been induced to various triaryl structures including trityl derivatives and triaryl boranes. For borane–amine adducts, such induced propeller chirality has not been reported yet due to the low energy barrier for racemization in common triarylboranes such as B(C6H5)3 or B(C6F5)3. Herein, we demonstrate that point chirality in side chains of chiral triarylborane–ammonia adducts, which feature intramolecular hydrogen bonds in addition to the dative N→B bond, can efficiently be transferred to triarylborane propeller chirality. Employing X-ray crystallography and ECD/VCD spectroscopy for structural characterizations, we investigate three examples with different steric demands of the incorporated chiral alkoxy side groups. We elucidate the conformational preferences of the molecular propellers. Furthermore, we show that computationally predicted conformational preferences obtained for the isolated, only implicitly solvated molecules are actually opposite to the experimentally observed ones.
Chemistry of Oxaziridines. 15. Asymmetric Oxidations Using 3-Substituted 1,2-Benzisothiazole 1,1-Dioxide Oxides
Davis, Franklin A.,ThimmaReddy, R.,McCauley, John P.,Przeslawski, Robert M.,Harakal, Mark E.,Carroll, Patrick J.
, p. 809 - 815 (2007/10/02)
The synthesis and asymmetric oxidations of chiral nonracemic 3-substituted 1,2-benzisothiazole 1,1-dioxide oxides (6) are described.These new N-sulfonyloxaziridines are prepared by oxidation of the corresponding enantiomerically pure sulfonimines 5.These reagents oxidize sulfides to sulfoxides (11-52percent ee), epoxidize nonfunctionalized alkenes (17-61percent ee), and oxidize enolates to α-hydroxy carbonyl compounds (11-81percent ee).Epoxidation of (-)-(S)-limonene with (+)-(2R,3S)-6a, a double asymmetric synthesis, affords a 93:7 cis/trans mixture of limonene oxides.Evaluation ofpossible transition-state structures suggests that the molecular recognition is primarily determined by steric factors.These reagents are less effective than N-sulfonyloxaziridines 1-3 in their asymmetric oxidations because they lack well-defined regions that are topologically dissimilar near the active site.
