Preparation of unsymmetrical ketones from tosylhydrazones and aromatic aldehydes via formyl C–H bond insertion

Preparation of ketones by insertion of diazo compounds into the formyl C−H bond of an aldehyde is an attractive procedure, but use of structurally diverse diazo compounds is hampered by preparation and safety issues. A convenient procedure for the synthesis of unsymmetrical ketones from bench-stable tosylhydrazones and aryl aldehydes is reported. The procedure can be performed in one pot from the parent carbonyl compound and needs only a base, with no additional promoters being required

GeoTagger: A Collaborative and Participatory Environmental Inquiry System

This note focuses on the motivation, approach, and the initial prototype implementation of Geotagger: a collaborative participatory environmental inquiry system. We situate the need for such a technology, and discuss related work - much of which is situated in the realm of citizen science. Our work uniquely distinguishes itself from many other citizen science applications in that it supports limited data collection and analysis, with the additional benefit of supporting social interactions and engagement through conversations about observed data. This is accomplished by creating friends and groups which are collaborators in the observational inquiry process

Azomethine ylides from nitrones: Using catalytic nBuLi for the totally stereoselective synthesis of trans-2-alkyl-3-oxazolines

The cycloaddition of azomethine ylide N-oxides (nitrone ylides) with aldehydes provides 3-oxazolines in a completely stereoselective manner in the presence of a catalytic amount of n-butyllithium. The process involves an initial nucleophilic attack on the aldehyde, followed by intramolecular oxygen addition to the nitrone moiety and lithium-assisted elimination of water, regenerating the catalytic species. Various Li-based catalytic systems are possible and the in situ generated water is required for continuing the catalytic cycle. The best results are observed with 20 mol % of n-butyllithium, whereas the use of stoichiometric amounts inhibit the rate of catalysis. Experimental, spectroscopic, and computational mechanistic studies have provided evidence of lithium-ion catalysis and rationalized several competing catalytic pathways.This work was supported by the Spanish Ministerio de Economía y Competitividad (MINECO) (project number CTQ2013-44367-C2-1-P), the Fondos Europeos para el Desarrollo Regional (FEDER), and the Gobierno de Aragón (Zaragoza, Spain, Biorganic Chemistry Group ,E-10). V. J.-N. thanks MINECO for a pre-doctoral grant (FPI program).Peer Reviewe