Dmitry N. Platonov

The cyclopropyliminium rearrangement of 2-cyclopropyl-4-nitrobenzimidazoles

Abstract2-Cyclopropyl-4(7)-nitrobenzimidazoles undergo the cyclopropyliminium rearrangement into two isomeric 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazoles, one isomer considerably dominating over the other. This reaction is more regioselective than those involving 5- or 6-substituted analogs, which is due to the electronic and steric effects of the nitro group as well as to stabilization of one intermediate by hydrogen bonding between the adjacent NH and NO2 fragments.

Estimating electron affinity from the lifetime of negative molecular ions: Cycloheptatriene derivatives

Cycloheptatriene derivatives are studied by means of resonance electron capture negative ion mass spectrometry (REC NIMS). The average lifetimes of molecular negative ions (NIs) are measured with respect to electron autodetachment. Using the Arrhenius approach, electron affinity EAa of the molecules under study is estimated, and the effective temperature of the resulting negative molecular ions is determined as a function of the electron energy. It is assumed that the dissociation of negative molecular ions in the ground electronic state is a process similar to that of the thermal degradation of molecules.

Hepta(methoxycarbonyl)cycloheptatriene halo derivatives

A reaction of potassium hepta(methoxycarbonyl)cycloheptatrienide with chlorine and bromine gave high yields of the corresponding chloroand bromohepta(methoxycarbonyl)cycloheptatrienes; the fluoro derivative was obtained by the exchange reaction of the corresponding bromide with silver fluoride. In contrast to the mentioned halides, the iodo derivative has proved unstable. Thermolysis of bromohepta(methoxycarbonyl)cycloheptatriene was studied, as well as its conversion to the azido and methoxy derivatives upon treatment with NaN3 or methanol.

Generation of 1-aryl-3-methoxycarbonylnitrilimines and their reaction with halogen-containing unsaturated compounds

Thermal decomposition of 1-(4-methoxyphenyl)- and 1-(4-fluorophenyl)hepta(methoxycarbonyl)-3a,7a-dihydroindazoles at 135 °C in the presence of allyl or propargyl halides leads to the elimination of hexamethyl benzenehexacarboxylate and the formation of the corresponding pyrazolines or pyrazoles as the products of 1,3-dipolar cycloaddition of 1-aryl-3-methoxycarbonylnitrilimines to the multiple bonds of the substrates used. In the case of vinyl halides, the products of the target reactions are either obtained in low yields or nonexistent, with a side conversions taking place instead. Thus, for example, in the case of 1,1-dichloro-4-methylpenta-1,3-diene, besides hexamethyl benzenehexacarboxylate, 3,5,5-trichloro-2-methylpent-4-en-2-ol and arylchlorohydrazones MeO2CC(Cl)=N-NHAr were unexpectedly isolated as the main products, as well.

Design of Multi-Component Reactions

Multi-component reactions (MCRs) have now been well established as a powerful synthetic tool for creating molecular complexity and diversity and are undoubtedly well suited for the drug discovery program. Another potential that has probably received less attention among synthetic chemists is the opportunity offered by MCRs for the development of new fundamentally important transformations (reactions). Indeed, although an MCR is composed of a series of known bimolecular reactions, the overall transformation could be novel. Consequently, it provides chemists the opportunities to uncover transformations that were otherwise difficult to realize. In this talk, we will present our recent work in this field, including: (1) the oxidative homologation of aldehydes to amides, (2) the oxidative coupling of aldehydes and isocyanides to α-ketoamides, (3) oxidative isocyanide-based MCRs, and (4) the enantioselective Passerini reaction.