641616-99-1Relevant academic research and scientific papers
Mechanistic investigations of cooperative catalysis in the enantioselective fluorination of epoxides
Kalow, Julia A.,Doyle, Abigail G.
, p. 16001 - 16012 (2011/11/13)
This report describes mechanistic studies of the (salen)Co- and amine-cocatalyzed enantioselective ring opening of epoxides by fluoride. The kinetics of the reaction, as determined by in situ 19F NMR analysis, are characterized by apparent first-order dependence on (salen)Co. Substituent effects, nonlinear effects, and reactivity with a linked (salen)Co catalyst provide evidence for a rate-limiting, bimetallic ring-opening step. To account for these divergent data, we propose a mechanism wherein the active nucleophilic fluorine species is a cobalt fluoride that forms a resting-state dimer. Axial ligation of the amine cocatalyst to (salen)Co facilitates dimer dissociation and is the origin of the observed cooperativity. On the basis of these studies, we show that significant improvements in the rates, turnover numbers, and substrate scope of the fluoride ring-opening reactions can be realized through the use of a linked salen framework. Application of this catalyst system to a rapid (5 min) fluorination to generate the unlabeled analog of a known PET tracer, F-MISO, is reported.
PROCESS FOR PREPARATION OF OPTICALLY ACTIVE 1-SUBSTITUTED AMINO-2,3-EPOXYPROPANES, INTERMEDIATES FOR THE SYNTHESIS THEREOF AND PROCESS FOR PREPARATION OF THE INTERMEDIATES
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Page/Page column 22-23, (2008/06/13)
The present invention provides an industrial process for effectively and advantageously preparing optically active 1-substituted amino-2,3-epoxypropanes useful as intermediates for preparing agricultural chemicals and medical products from optically activ
