An enaminone-directed benzannulation/macrocyclization approach to cyclophane ring systems

A straightforward and modular preparative approach to 1,3,5-triaroylbenzene-based functionalized cyclophane ring systems has been developed. The key cyclophane-forming macrocyclization reaction was accomplished during the course of a regioselective cross-benzannulation between bis(aryl ethynyl) ketone and enaminone reactants. Macrocyclic products with ring sizes ranging from 18- to 22-membered were successfully constructed. The composition of the tether connecting the two aryl ethynyl ketone fragments can be easily varied; consequently, this method is suitable for construction of a diverse range of structurally distinct cyclophane products. To illustrate this feature, cyclophanes possessing xylyl, alkyl, di(ethylene triamine), and di(ethylene oxy) bridging units were synthesized in isolated yields of 11-46%. Three new cyclophanes (calixarene-like macrocyles 8 and 9, as well as crownophane 18) were structurally characterized by X-ray diffractometry.     

Effects of Gold and Silver Nanoparticles on Optical Bistability of Titanium Dioxide Nanocolloid

Physics of the Solid State - In this study, titanium dioxide (TiO2) nanocolloid was synthesized through sol–gel method, and nonlinear optical properties were studied using z-scan method. The...     

Modular synthesis of triaroylbenzene-derived crownophanes

An isomeric series of homologous crownophanes (i.e., macrocycles possessing structural features of crown ethers and cyclophanes) has been prepared via a concise and modular synthetic route. Macrocyclization is achieved in reasonable yield during the course of an enaminone-triggered benzannulation with bis(aryl ethynyl ketone) reaction partners. The crownophanes examined were active alkali cation binding agents in the gas phase, but failed to exhibit ionophoric properties in solution. On the basis of X-ray crystallographic analysis, it is concluded that the cyclophane framework of these macrocycles is too large and rigid to allow efficient interaction with the cations examined.