1072879-63-0Relevant academic research and scientific papers
Multicomponent Catalytic Asymmetric Synthesis of trans-Aziridines
Zhou, Yubai,Gupta, Anil K.,Mukherjee, Munmun,Zheng, Li,Wulff, William D.
, p. 13121 - 13140 (2017/12/26)
A multicomponent trans-aziridination of aldehydes, amines, and diazo compounds with BOROX catalysts is developed. The optimal protocol is slightly different for aryl aldehydes than for aliphatic aldehydes. The key to the success with aryl aldehydes was allowing the catalyst, aldehyde, and amine to react for 20 min before addition of the diazo compound. A variety of 11 different electron-poor and electron-rich aryl aldehydes were screened to give trans-aziridines in 73-90% yield with 82-99% ee and trans/cis selectivities of 19:1 to >99:1. The optimal protocol for the trans-aziridination of aliphatic aldehydes did not require prereaction of the catalyst, aldehyde, and amine, and instead, the diazo compound could be added directly. The scope of the reaction is limited to unbranched aliphatic aldehydes and was tolerant of a number of functional groups including ethers, esters, epoxides, carbamates, and phthalimides. A total of 10 aliphatic aldehydes were examined and found to give trans-aziridines in 60-88% yield with 60-98% ee and trans/cis selectivities of 6:1 to >99:1. Alkenyl aldehydes did not react, but an alkynyl aldehyde gave a 71% yield and 95% ee of an aziridine that was found to be the cis- and not the trans-diastereomer. The aryl and aliphatic aldehydes both gave the trans-aziridines with the same absolute configuration with the same catalyst; however, in those cases where cis-aziridines were formed, the configuration was opposite for those formed from aryl versus aliphatic aldehydes.
BOROX catalysis: Self-assembled AMINO-BOROX and IMINO-BOROX chiral Bronsted acids in a five component catalyst assembly/ catalytic asymmetric aziridination
Gupta, Anil K.,Mukherjee, Munmun,Hu, Gang,Wulff, William D.
supporting information, p. 7932 - 7944,13 (2020/10/15)
A five-component catalyst assembly/aziridination reaction is described starting from an aldehyde, an amine, ethyl diazoacetate, B(OPh)3, and a molecule of a vaulted biaryl ligand (VAPOL or VANOL). A remarkable level of chemoselectivity was observed since, while 10 different products could have resulted from various reactions between the five components, an aziridine was formed in 85% yield and 98% ee and only two other products could be detected in 3% yield. Studies reveal that the first in a sequence of three reactions is an exceedingly rapid amine-induced assembly of an AMINOBOROX chiral Bronsted acid species from VAPOL and B(OPh)3, which is followed by imine formation from the amine and aldehyde and the concomitant formation of an IMINO-BOROX chiral Bronsted acid and finally the reaction of the imine with ethyl diazoacetate mediated by the IMINO-BOROX catalyst to give aziridine-2-carboxylic esters with very high diastereo- and enantioselectivity.
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.
Seeking passe-partout in the catalytic asymmetric aziridination of imines: Evolving toward substrate generality for a single chemzyme
Mukherjee, Munmun,Gupta, Anil K.,Lu, Zhenjie,Zhang, Yu,Wulff, William D.
supporting information; experimental part, p. 5643 - 5660 (2010/11/18)
The asymmetric catalytic aziridination reaction (AZ reaction) of imines derived from dianisylmethyl (DAM) amine and tetra-methyldianisylmethyl (MEDAM) amine were examined with boroxinate catalysts prepared from both the VANOL and VAPOL ligands. This included an evaluation of different protocols for the preparation of the catalyst. The AZ reaction of DAM and MEDAM imines prepared from nine different aryl and aliphatic aldehydes were examined. The MEDAM imines were superior to the DAM imines in the AZ reaction, giving much higher asymmetric inductions and higher overall yields of aziridines. The MEDAM imines were found to also be superior to the previously studied diphenylmethyl (benzhydryl or Bh) and tetra-tert-butyldianisylmethyl (BUDAM) imines especially for imines derived from aliphatic aldehydes. The average asymmetric induction over the nine different MEDAM imines studied was 97% ee with the VAPOL catalyst and 96% ee with the VANOL catalyst. The MEDAM imines can be deprotected to give N-H aziridines in all cases except for some electron-rich aryl aldehydes. The MEDAM imines are much more reactive than benzhydryl imines, and this was most evident when a diazoacetate ester is replaced by a diazoacetamide. The less reactive diazoacetamides give very low yields in their reactions with benzhydryl imines but high yields with MEDAM imines.
Mapping the active site in a chemzyme: Diversity in the N-substituent in the catalytic asymmetric aziridination of imines
Zhang, Yu,Lu, Zhenjie,Desai, Aman,Wulff, William D.
supporting information; experimental part, p. 5429 - 5432 (2009/06/20)
(Chemical Equation Presented) The active site of the aziridination catalyst derived from either the VANOL or VAPOL ligand and B(OPh)3 is larger than expected and can accommodate not only significant substitution on the diarylmethyl unit of the imine but also that alkyl (but not perfluorylalkyl) substituents on the aryl groups lead to enhanced rates and enantioselection. The screen of diarylmethyl N-substituents on the imine revealed that the 3,5-di-tert-butyldianisylmethyl group (BUDAM) gave exceptionally high asymmetric inductions for imines of aryl aldehydes.
