Biginelli reactions have been monitored by direct infusion electrospray ionization mass spectrometry (ESI-MS) and key cationic intermediates involved in this three-component reaction have been intercepted and further characterized by tandem MS experiments (ESI-MS/MS). Density functional theory calculations were also used to investigate the feasibility of the major competing mechanisms proposed for the Biginelli reaction. The experimental and theoretical results were found to corroborate the iminium mechanism proposed by Folkers and Johnson, whereas no intermediates directly associated with either the more energy demanding Knoevenagel or enamine mechanisms could be intercepted.

Aryldiazonium tetrafluoroborates have been successfully employed in the direct and regioselective arylation of heteroaromatics such as indole, benzofuran and benzothiophene. The cationic aryl palladium intermediates derived from the aryldiazonium salts act as effective electrophiles in the process. These arylating reactions display operational simplicity and provide the arylated heterocycles regioselectively in moderate to excellent yields.

The superacid-promoted reactions of alpha-hydroxy and alpha-ketoamides have been studied. Ionization of these compounds leads to varied aryl-substituted oxyindole products. In some cases, electrocyclization can lead to substituted fluorene products. Dicationic, superelectrophilic intermediates are proposed as intermediates leading to the products from alpha-hydroxy and alpha-ketoamides.

The highly pyramidalized molecule bisnoradamantene is extremely reactive toward nucleophiles and dienes. In this work, we studied the electronic structure of bisnoaradamantene, as well as those of its cation and dication, which are previously unreported carbonium ions. According to QTAIM and MO analysis, there is a 3c-2e bonding system in the bisnoradamantenyl cation and a 4c-2e bonding system in the bisnoradamantenyl dication. A topological study indicated that, on going from bisnoradamantene to its dication, π-bond interaction with the bridgehead carbon atom increases. Additional study of the bisnoradamantanyl dication also indicated that it has two multicenter bonding systems. Comparison of the D3BIA and NICS aromaticity indices of these molecules and other derivatives indicates that these indices are well correlated, and analysis of these indices shows that the cationic and dicationic bisnoradamantenyl species are homoaromatic.

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Indole derivatives R 0140Superacid-Promoted Reactions of α-Ketoamides and Related Systems. -Treatment of aryl-substituted α-ketoamides with arenes and TfOH allows a new access to oxindoles of type (III). However, the naphthyl amide (VII) gives a benzoquinolinone. Starting from alkyl-substituted α-ketoamides, unsaturated amides like (X) are obtained. Reaction of the hydroxyamide (XI) with TfOH also provides an oxindole, but the diarylated analogues (XIII) yield fluorene derivatives. -(SAI, K. K. S.; ESTEVES, P. M.; DA PENHA, E. T.; KLUMPP*, D. A.; J.

Expeditious Synthesis of 3,4-Dihydroisocoumarins and Phthalides Using the Heck-Matsuda Reaction. -Reaction of diazonium salt (I) with electron-rich styrenes gives isocoumarins,whereas electron deficient-olefins provide phthalides. A one-pot procedure is developed for the preparation of the unsaturated analogue (IV). In the case of substrate (VII), extension of the reaction time allows complete deprotection to produce the phenolic product (VIII). -(DA PENHA, E. T.; FORNI, J. A.; BIAGOLI, A. F. P.; CORREIA*, C. R. D.; Tetrahedron Lett. 52 (2011) 48, 6342-6345, http://dx.

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