Current Organic Chemistry - Volume 20, Issue 10, 2016

Calixarenes are supramolecular structures characterized by their “calix” shape and their easy synthetic accessibility. They are amphiphilic in nature, thus they can bear in their structure both hydrophobic and hydrophilic features as well as charged groups. They are characterized by architectural plasticity responsible for their unique fine-tuned properties that can be shaped for an array of applications. Herein, we will focus, on their diverse available applications, and give special emphasis on biocatalysis and cancer therapy as two modern directions and emerging fields of interest that have been sporadically explored in the literature and can pave the way for the discovery of novel therapeutics. This review provides the first exhaustive examination on the enhanced catalytic activity and selectivity of calixarene-based encapsulated biocatalysts towards the synthesis of bioactive molecules. The application of functionalized calixarenes in cancer therapy is also analyzed towards the spatiotemporal control they can offer in targeted drug delivery.

As one of the most important chemical reactions, SN2 reactions play a central role in both synthetic chemistry and the development of mechanistic paradigms. Most of the previous attention has centered on substitution at carbon, whereas displacement at nitrogen is clearly less studied and less understood. The SN2@N reactions have enormous synthetic potential, especially in heterocyclic chemistry, which is a cornerstone of medicinal chemistry, and has been receiving increasing attention, both experimentally and computationally. In this review, we outline the experimental and theoretical studies on the gas-phase SN2 reactions at nitrogen in recent years, and make comprehensive comparisons between gasphase SN2 at carbon and at nitrogen. Some new structure-energy relationships have been proposed. Meanwhile, the similarities and differences of the α-Effect, which refer to the increased nucleophilicity relative to a given basicity for nucleophiles with one or more pairs of unshared electrons adjacent to the attacking atom, between the gas-phase SN2@C and SN2@N reactions are discussed.

Benzofuran derivatives and benzofuransare presented as scaffolds in complex molecules and have attracted much attention and prevalent interest due to their interesting biological activity. They also exist in several numbers of naturally occurring compounds and exhibiting biological activity. In this review, we will try to underscore the reactivity of benzofurans through comprehension and giving a full perspective to the readers.

The mechanism for the T3P®-promoted derivatizations of five-membered cyclic phosphinic acids was studied by theoretical calculations using the DFT method at the B3LYP/6- 31g(d,p)\\6-311g(2d,2p) level in order to elucidate the role of T3P® and interpret the experimental results. The esterification and amidation of 1-hydroxy-3-methyl-3-phospholene 1-oxide, along with the esterification of 1-hydroxy-3,4-dimethylphospholane oxide with special regard to the diastereoselectivity of the latter reaction were investigated. While the direct derivatizations with butanol and butylamine were found to be slightly exothermic and endothermic, respectively, in the presence of the T3P® reagent, the energetics of the derivatizations became by -59.2 kJ mol-1 and -31.6 kJ mol-1 exothermic, respectively. In the latter case, the reactions take place via the adduct of the cyclic phosphinic acid and the T3P® reactant. The unexpected diastereoselectivity observed in the T3P®-assisted esterification of the 1-hydroxy- 3,4-dimethylphospholane oxide was explained by a steric effect.

Nano-ferroferric oxide (Nano-Fe3O4) can be used as a ferrite absorbing material when exposed to microwave absorption due to its high magnetic permeability. However, a single nanometer-sized material has a narrow frequency range for its reflection absorption wave during the secondary polymerization process used for preparing nanomaterials. In this study, mesoporous materials and nano-Fe3O4 were used to prepare a nano-Fe3O4 mesoporous composite, which employs the complex permeability of the material to improve the absorption performance of the composites. The materials were characterized and the influence of absorption performance from chemical coprecipitation and encapsulation of suspension polymerization were investigated. The experimental results indicate that suspension polymerization produces materials with enhanced microwave absorption compared to chemical coprecipitation. In addition, results show that “microscopic structure trigger loss of resonance” is critical for the absorbance of composite materials. Furthermore, the eigen frequency of nano-Fe3O4was calculated.