1522-33-4Relevant academic research and scientific papers
Catalytic Asymmetric Epoxidation of Aldehydes with Two VANOL-Derived Chiral Borate Catalysts
Gupta, Anil K.,Yin, Xiaopeng,Mukherjee, Munmun,Desai, Aman A.,Mohammadlou, Aliakbar,Jurewicz, Kelsee,Wulff, William D.
supporting information, p. 3361 - 3367 (2019/02/16)
A highly diastereo- and enantioselective method for the epoxidation of aldehydes with α-diazoacetamides has been developed with two different borate ester catalysts of VANOL. Both catalytic systems are general for aromatic, aliphatic, and acetylenic aldehydes, giving high yields and inductions for nearly all cases. One borate ester catalyst has two molecules of VANOL and the other only one VANOL. Catalysts generated from BINOL and VAPOL are ineffective catalysts. An application is shown for access to the side-chain of taxol.
Internal Alkyne Regio- and Chemoselectivity using a Zwitterionic N-Heterocyclic Carbene Gold Catalyst in a Silver-Free Alkyne Hydration Reaction
Weerasiri, Kushan C.,Chen, Danmin,Wozniak, Derek I.,Dobereiner, Graham E.
, p. 4106 - 4113 (2016/12/30)
An alkyne hydration of terminal and internal alkynes is reported using a zwitterionic N-heterocyclic carbene gold catalyst [(BNHC)Au(SMe2)] in the absence of silver and Br?nsted acid additives. The hydration demonstrates good regioselectivity in alkyne hydration and chemoselectivity for internal alkynes vs. terminal. In addition, (BNHC)Au(SMe2) performs a propargyl alcohol hydration to predominantly form α-hydroxymethyl ketone over the more common Meyer–Schuster rearrangement product. While complex (BNHC)Au(SMe2) is active without silver additives, addition of silver hexafluoroantimonate (AgSbF6) increases reaction rate and decreases selectivity for internal alkyne hydration over terminal substrates. To the best of our knowledge, the rate enhancement of (BNHC)Au(SMe2) by AgSbF6is the first such demonstration of a silver effect for a “halide-free” Au catalyst. (Figure presented.).
Safe generation and direct use of diazoesters in flow chemistry
Müller, Simon T. R.,Smith, Daniel,Hellier, Paul,Wirth, Thomas
, p. 871 - 875 (2014/04/03)
A safe and fast method for the production of β-hydroxy-α- diazoesters in continuous flow technology is described. The synthesis involves the formation of ethyl diazoacetate in situ and the addition to several aldehydes in a two-step continuous flow microreactor setup. Rhodium acetate catalyzes a subsequent 1,2-hydride shift to give access to β-keto esters in a three-step sequence. Georg Thieme Verlag Stuttgart · New York.
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.
