Kinetic Resolution of alpha-Acetoxy-N-Acyl Oxazolidinethiones by a Chiral O-Nucleophilic Acyl Transfer Catalyst

We recently described a series of catalysts bearing a hydroxyl group in close proximity to a basic amine which effect the methanolysis of para-nitrophenyl (PNP) esters.1 These catalysts, an example of which is provided in Scheme 1, operate by an Onucleophilic mechanism in which the hydroxyl group of the catalyst (1) undergoes base-catalyzed acylation by the PNP ester (2) to give an acyl-transferred intermediate (3). This intermediate then undergoes base-catalyzed deacylation to provide the product (4) and regenerate the catalyst (1). In the course of our studies, we found that the deacylation step of the catalytic cycle is turnover-limiting, and that catalysts containing alcohols with a proximal electron withdrawing group are more active, probably due to their enhanced leaving group ability. The catalysts we studied are chiral, and in this communication we describe the use of two such catalysts for the kinetic resolution of chiral α-acetoxy oxazolidinethione imides

Doubly Vinylogous Aldol Reaction of Furoate Esters with Aldehydes and Ketones

The use of bulky Lewis acids, aluminum tris­(2,6-diphenylphenoxide) (ATPH) and aluminum tris­(2,6-di-2-naphthylphenoxide) (ATNP), in the doubly vinylogous aldol reaction between methyl-5-methyl-2-furoate and aldehydes or ketones is described. These reactions proceed smoothly and in high yields with both enolizable and non-enolizable substrates. This C–C bond-forming reaction enables a new bond construction for the synthesis of functionalized furans

Xinqiang Xu

In this paper, a multiphysics, finite element computational model for a hybrid concentrating photovoltaic/thermal (CPV/T) water collector is developed. The collector consists of a solar concentrator, 18 single junction germanium cells connected in series, and a water channel cooling system with heat-recovery capability. The electrical characteristics of the entire module are obtained from an equivalent electrical model for a single solar cell. A detailed thermal and electrical model is developed to calculate the thermal and electrical characteristics of the collector at different water flow rates. These characteristics include the system temperature distribution, outlet water temperature and the thermal and electrical efficiencies. The model is used to study the effect of flow rate on the efficiencies. It is found that both efficiencies improve as the flow rate increases up to a point (0.03 m/s), and after that point remain at relatively constant levels. However, as the flow rate increases the outlet water temperature decreases, reducing the quality of the extracted thermal energy. In addition to the thermal and electrical modeling, finite element analysis is used to estimate the fatigue life of the module based on the different temperature profiles obtained from the thermal model at flow rates of 0.01 m/s and 0.03 m/s. Results show that for the higher flow rate, the outlet water temperature decreases, but the fatigue life improves. Based on the fatigue life model predictions, it is shown that the thickness of die attach layer must be increased for high outlet temperature applications of the hybrid CPV/T collector

Select steroid hormone glucuronide metabolites can cause toll-like receptor 4 activation and enhanced pain

Abstract not availableSusannah S. Lewis, Mark R. Hutchinson, Morin M. Frick, Yingning Zhang, Steven F. Maier, Tarek Sammakia, Kenner C. Rice, Linda R. Watkin