Ernest W. Robb

Microwave-Induced Organic Reaction Enhancement (More) Chemistry: Techniques for Rapid, Safe and Inexpensive Synthesis

Synthetic organic reactions have been conducted under microwave irradiation in open vessels in unaltered domestic microwave ovens. Reaction times vary from a few seconds for sub-milligram reactions to about 15 minutes for reactions carried out on a scale of hundreds of grams. Promising results have been obtained for several condensations, as well as the Bischler-Napieralski reaction, the Wolff-Kishner reduction, free radical dehalogenation reactions, and other standard synthetic operations. Rapid catalytic transfer hydrogenation using ammonium formate as the source of hydrogen has been conducted at about 100-130 °C under microwave irradiation.Meaningful, safe and inexpensive synthetic experiments for undergraduate and pre-college students have been developed and tested. The MORE chemistry techniques make it possible to use simple apparatus and very short reaction times.Commercial microwave ovens are now essential equipment in our research and teaching laboratories [1-3]. These ovens are relatively inexpensive, easy to move from one laboratory and set up in another, and safe to operate. Glass, plastics, and ceramics are essentially transparent to microwaves whereas many organic compounds are dipolar in nature and absorb microwave energy readily. We have found that untraditional experimental arrangements are possible for conducting a wide variety of organic reactions in open vessels inside domestic microwave ovens. Depending on the quantity of reactants, most reactions (on a scale of milligrams to several grams) can be completed in minutes instead of hours. One important element of our “Microwave-induced Organic Reaction Enhancement” (MORE) chemistry is the proper choice of a microwave energy transfer agent as the reaction medium.

A neural network approach to infrared spectrum interpretation

The simple linear neural network model was investigated as a method for automated interpretation of infrared spectra. The model was trained using a database of infrared spectra of organic compounds of known structure. The model was able to learn, without any prior input of spectrum-structure correlations, to recognize and identify 76 functional groupings with accuracies ranging from fair to excellent. The effect of network input parameters and of training set composition were studied, and several sources of spurious correlations were identified and corrected.

Neural network models for infrared spectrum interpretation

A neural network model having a layer of hidden units is described which can identify functional groups in organic compounds, based on their infrared spectra. This network shows substantially better performance than the simple linear model reported earlier. The effect of the training set size and composition, the number of hidden units used, and the training time were studied.

Microwave-assisted rapid synthesis of α-amino-β-lactams

Abstract A rapid and convenient approach to α-amino-β-lactams has been developed using the tetrachlorophthalimido group as a masked amino substituent. Reaction between glycine and tetrachlorophthalic anhydride in DMF for about 90 sec in a domestic microwave oven led to an imidoacetic acid in high yield; the corresponding acid chloride reacted with Schiff bases to provide mixtures of trans and cis β-lactams. Nearly exclusive formation of trans β-lactams could be achieved in some cases in a few minutes by conducting β-lactam formation under strong microwave irradiation. Facile conversion to α-amino-β-lactams was realized in 5–10 minutes via solventless reaction of these α-amino-β-lactams with ethylenediamine at room temperature.

b-Lactam Formation via Enolate Addition: An Unexpected Methelenation Reaction

The condensation of ethyl phenylacetate or ethyl β-hydroxybutyrate with Schiff bases in presence of an excess of lithium diisopropylamide or lithium hexamethyldisilazide leads to unsaturated amines instead of the expected β-lactams