Dihydropyrimidin-2-(1H)-ones have been synthesized in excellent yields in short reaction time at ambient temperature in the absence of any added catalyst by the reaction of aromatic or aliphatic aldehydes with ethyl acetoacetate (EAA) and urea (or thiourea) in room temperature ionic liquid (IL) under ultrasound irradiation. The evidence for the role of IL in promoting this multicomponent reaction has been given. Based on this evidence, a plausible mechanistic pathway has been postulated.

The O-acetylation of alcohols with acetic anhydride to the corresponding esters has been achieved in excellent isolated yields in short reaction time at ambient conditions under ultrasonic irradiation in the absence of any added catalyst using a room temperature ionic liquid as the medium as well as a promoter for the reaction. The products could be isolated by distillation or selective extraction from the non-volatile ionic liquid, which could be recycled giving rise to a process with minimal waste.

The Sonogashira reaction proceeds at ambient temperature (30 degrees C) in acetone or room-temperature ionic liquid, 1,3-di-n-butylimidazolium tetrafluoroborate ([bbim]BF4), as solvent under ultrasound irradiation to give enhanced reaction rates, excellent chemoselectivity, and high yields in the absence of a copper cocatalyst and a phosphine ligand. TEM analysis showed the formation of stable, crystalline, and polydispersed Pd(0) nanoparticles as catalyst for the reaction.

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The condensation reaction involving an aldehyde and diketone was efficiently promoted by the Ionic liquid, [Hbim]BF(4) (IL) as a reaction medium with methanol as co-solvent at ambient temperature under ultrasonic irradiation to afford the corresponding 1,8-dioxo-octahydro-xanthene (xanthene) derivatives in excellent yields. The advantages of this method include among others the use of a recyclable, non-volatile ionic liquid, which promotes this protocol under ambient temperature without the requirement of any added catalyst. The reaction times and yields are compared with p-TSA catalyzed synthesis of xanthenes under thermal conditions, which is also reported for the first time under our reaction conditions.

ABSTRACT. An efficient and simple method was developed for the synthesis pyrimidine-5-carboxamides using UO2(NO3)2.6H2O catalyst under conventional and microwave irradiation. The synthesis of dihydropyrimidine using uranyl nitrate had shown many advantages such as easy work up, shorter reaction times and higher yields using acetonitrile as a solvent. The structures of the synthesized compounds were confirmed by FT-IR, 1 H NMR, 13 C NMR and mass spectral data. All the synthesized compounds screened for in vitro antioxidant and antibacterial activity and the results are reported.

The rearrangement of methyl 2-(methy1thio)benzenesulfonate (1) to the zwitterionic 2-(dimethylsu1fonium)benzenesulfonate (2) is known to proceed in solution by intermolecular Me transfers. The same rearrangement has been observed to occur in crystalline 1, but the crystal structure shows that the molecular packing is not conducive to intermolecular Me transfer. The reaction has been carried out with mixed crystals composed of 1 and deuteriomethylated (DJ-1. By fast-atom-bombardment mass spectroscopy, it has been shown that the product consists of a 1:2:1 mixture of the non-, tri-, and hexadeuterated species, the mixture expected, if the solid-state reaction proceeds by intermolecular Me transfers. From this result, together with the slower rates of conversion in the single crystal compared with the melt, it can be concluded that the reaction must occur not topochemically but rather at defects such as microcavities, surfaces, and other irregularities in the ordered crystal arrangement.Bergman and coworkers [l] have shown that the Me-transfer reaction of methyl 2-(dimethy1amino)benzenesulfonate (3) to the corresponding zwitterionic trimethylammonium sulfonate (4) proceeds much faster in the crystalline state than in solution or in the melt. They determined the crystal structure of 3 and showed that it contained a particularly favourable arrangement of molecules for intermolecular Me transfer; the rate acceleration in the crystal was then explained as a topochemical effect [ 2 ] . During a sabbatical leave in Ziirich, one of us (K.V.) noticed that the atomic displacement parameters obtained in the crystal structure analysis of 3 indicated a librational motion of the molecules that could move the reacting centers along the putative reaction coordinate (an indication that has recently been confirmed by a redetermination of the crystal structure at 193 and 255 K[3]). Following this observation, K.V. became interested in the question of determining the crystal structure of methyl 2-(methy1thio)benzenesulfonate (1) and studying its solid-state behaviour. It was already known from the Zurich study of S, reactions involving endocyclic transition states [4][5][6] that the Me-transfer reaction leading from 1 to the zwitterionic product 2-(dimethylsulfonium)benzenesulfonate (2) proceeds not intra-but intermolecularly in solution.

Abstract. M r = 251.34, monoclinic, P21/n, a =