New methods for preparation of tailor-made fluorine-containing compounds are in extremely high demand in nearly every sector of chemical industry. The asymmetric construction of quaternary C−F stereogenic centers is the most synthetically challenging and, consequently, the least developed area of research. As a reflection of this apparent methodological deficit, pharmaceutical drugs featuring C−F stereogenic centers constitute less than 1% of all fluorine-containing medicines currently on the market or in clinical development. Here we provide a comprehensive review of current research activity in this area, including such general directions as asymmetric electrophilic fluorination via organocatalytic and transition-metal catalyzed reactions, asymmetric elaboration of fluorine-containing substrates via alkylations, Mannich, Michael, and aldol additions, cross-coupling reactions, and biocatalytic approaches.
CONTENTS
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Abstract:La(OH) 3 -modified exfoliated vermiculites were fabricated, characterized, and investigated for phosphate removal in batch tests for the first time. The BET surface area of the La 5 EV adsorbent, which was synthesized in the solution consisting of 5.00 mmol/g La/exfoliated vermiculite (EV), was significantly increased, accompanied with a larger pore diameter and greater total pore volume, as compared with the unmodified EV. The phosphate adsorption capacity of La 5 EV was approximately one order of magnitude higher than that of EV. Effects of initial phosphate concentration, contact time, temperature, pH, and 2 co-existing ions on the adsorption capacity of La 5 EV were investigated in detail. The experimental equilibrium data were fitted better by using the Langmuir model (maximum adsorption capacity of 79.6 mg P/g) than the Dubinin-Radushkevich or the Freundlich model, suggesting that the adsorption feature be monolayer. Meanwhile, the phosphate adsorption kinetics could be well described by the pseudo-second-order model, and the adsorption process might be controlled by boundary layer (film) diffusion. ∆G°, ∆H° and ∆S° were also determined, in which it was found that the phosphate adsorption , and SO 4 2-had neglectable effects on its phosphate removal capacities. In the synthetic secondary treated wastewater with a low phosphate concentration of 2 mg P/L, 97.9 % of its final adsorption capacity reached in the first 10 min and the phosphate concentration dramatically decreased below 50 µ g P/L. The spent La 5 EV could be regenerated and reused in phosphate adsorption; that could remove more than 70 % phosphate in the 3 rd adsorption-desorption cycle.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.