Intramolecular Pd-catalyzed carboetherification and carboamination. Influence of catalyst structure on reaction mechanism and product stereochemistry

The intramolecular Pd-catalyzed carboetherification of alkenes affords 2-indan-1-yltetrahydrofuran products in moderate to good yield with good to excellent levels of diastereoselectivity. The stereochemical outcome of these reactions is dependent on the structure of the Pd catalyst. Use of PCy(3) or P[(4-MeO)C(6)H(4)](3) as the ligand for Pd leads to syn-addition of the arene and the oxygen atom across the double bond, whereas use of (+/-)-BINAP or DPP-benzene affords products that result from anti-addition. The catalyst-induced change in stereochemistry is likely due to a change in reaction mechanism. Evidence is presented that suggests the syn-addition products derive from an unprecedented transannular alkene insertion of an 11-membered Pd(Ar)(OR) complex. In contrast, the anti-addition products appear to arise from Wacker-type anti-oxypalladation. Studies on analogous Pd-catalyzed intramolecular carboamination reactions, which afford 2-indan-1-ylpyrrolidines that result from syn-addition, are also described.     

Recent developments in multiphysics computational models of physiological flows

A mini-symposium on computational modeling of fluid–structure interactions and other multiphysics in physiological flows was held at the 11th World Congress on Computational Mechanics in July 2014 in Barcelona, Spain. This special issue of Theoretical and Computational Fluid Dynamics contains papers from among the participants of the mini-symposium. The present paper provides an overview of the mini-symposium and the special issue.     

Iterated nearest neighbors and finding minimal polytopes

We introduce a new method for finding several types of optimalk-point sets, minimizing perimeter, diameter, circumradius, and related measures, by testing sets of theO(k) nearest neighbors to each point. We argue that this is better in a number of ways than previous algorithms, which were based on high-order Voronoi diagrams. Our technique allows us for the first time to maintain minimal sets efficiently as new points are inserted, to generalize our algorithms to higher dimensions, to find minimal convexk-vertex polygons and polytopes, and to improve many previous results. We achieve many of our results via a new algorithm for finding rectilinear nearest neighbors in the plane in timeO(n logn+kn). We also demonstrate a related technique for finding minimum areak-point sets in the plane, based on testing sets of nearest vertical neighbors to each line segment determined by a pair of points. A generalization of this technique also allows us to find minimum volume and boundary measure sets in arbitrary dimensions. Portions of this paper were presented at the 3rd and 4th ACM-SIAM Symposia on Discrete Algorithms [17], [19]. This paper includes work done while Jeff Erickson was at the University of California at Irvine. David Eppstein's research was partially supported by NSF Grant CCR-9258335.     

DNA microarray technology used for studying foodborne pathogens and microbial habitats: minireview

Microarray analysis is an emerging technology that has the potential to become a leading trend in bacterial identification in food and feed improvement. The technology uses fluorescent-labeled probes amplified from bacterial samples that are then hybridized to thousands of DNA sequences immobilized on chemically modified glass slides. The whole gene or open reading frame(s) is represented by a polymerase chain reaction fragment of double-strand DNA, approximately 1000 base pair (bp) or 20-70 bp single-strand oligonucleotides. The technology can be used to identity bacteria and to study gene expression in complex microbial populations, such as those found in food and gastrointestinal tracts. Data generated by microarray analysis can be potentially used to improve the safety of our food supply as well as ensure the efficiency of animal feed conversion to human food, e.g., in meat and milk production by ruminants. This minireview addresses the use of microarray technology in bacterial identification and gene expression in different microbial systems and in habitats containing mixed populations of bacteria.     

Use of statistical design of experiments in the optimization of amide synthesis utilizing polystyrene-supported N-hydroxybenzotriazole resin

Two fields that routinely perform reaction optimization studies are chemical development (prior to scale-up) and medicinal or combinatorial chemistry (prior to analogue synthesis or library production). To date, the use of statistical design of experiments (DoE) in conjunction with automated synthesizers has been applied in process research to a greater extent than in the medicinal or combinatorial laboratories. We have applied DoE in conjunction with an automated synthesizer to optimize the synthesis of amides employing resin-bound N-hydroxybenzotriazole (PS-HOBt) active esters as intermediates. This methodology allowed the rapid development of an improved protocol for the parallel synthesis of amides by conversion of carboxylic acids to PS-HOBt esters followed by treatment with appropriate amines. Product isolation involved only simple filtration and evaporation.     

Acid-catalyzed oxygen-transfer reactions of ortho-alkenyldimethylbenzylamine oxides

Several ortho-alkenyldimethylbenzylamine oxides were found to rearrange in strong acid media to mixtures of aminophthalans and conjugated aminoketones     

Bach-flat asymptotically locally Euclidean metrics

We obtain a volume growth and curvature decay result for various classes of complete, noncompact Riemannian metrics in dimension 4; in particular our method applies to anti-self-dual or Kähler metrics with zero scalar curvature, and metrics with harmonic curvature. Similar results were obtained for Einstein metrics in [And89], [BKN89], [Tia90], but our analysis differs from the Einstein case in that (1) we consider more generally a fourth order system in the metric, and (2) we do not assume any pointwise Ricci curvature bound.