Chiral Calix[3]pyrrole Derivatives: Synthesis, Racemization Kinetics, and Ring Expansion to Calix[9]- and Calix[12]pyrrole Analogues.

Chiral pyrrolic macrocycles continue to attract interest. However, their molecular design remains challenging. Here, we report a calixpyrrole-based chiral macrocyclic system, calix[1]furan[1]pyrrole[1]thiophene (1), synthesized from an oligoketone.

Determination of the critical chain length for macromolecular crystallization using structurally flexible polyketones.

Critical chain length that divides small molecule crystallization from macromolecular crystallization is an important index in macro-organic chemistry to predict chain-length dependent properties of oligomers and polymers. However, extensive research on crystallization behavior of individual oligomers has been inhibited by difficulties in their synthesis and crystallization. Here, we report on the determination of critical chain length of macromolecular crystallization for structurally flexible polyketones consisting of 3,3-dimethylpentane-2,4-dione.

Alkali metal ion binding using cyclic polyketones.

Cyclic oligoketones composed of 3,3-dimethylpentane-2,4-diones showed crown ether-like alkali metal ion binding behavior with association constants up to 1.7 × 10 M in chloroform/acetonitrile (v/v, 9/1). The binding properties have been used for catalysis in the Finkelstein reaction in a low-polarity solvent.

Strain-Induced Ring Expansion Reactions of Calix[3]pyrrole-Related Macrocycles.

The recent discovery of calix[3]pyrrole, a porphyrinogen-like tripyrrolic macrocycle, has provided an unprecedented strain-induced ring expansion reaction into calix[6]pyrrole. Here, we synthesized calix[n]furan[3-n]pyrrole (n=1∼3) macrocycles to investigate the reaction scope and mechanism of the ring expansion. Single crystal X-ray analysis and theoretical calculations revealed that macrocyclic ring strain increases as the number of inner NH sites increases.

Calix[3]pyrrole: A Missing Link in Porphyrin-Related Chemistry.

A long-standing question in porphyrin chemistry is why pyrrole monomers selectively form tetrapyrrolic macrocycles, whereas the corresponding tripyrrolic macrocycles are never observed. Calix[3]pyrrole, a tripyrrolic porphyrinogen-like macrocycle bearing three sp-carbon linkages, is a missing link molecule that might hold the key to this enigma; however, it has remained elusive. Here we report the synthesis and strain-induced transformations of calix[3]pyrrole and its furan analogue, calix[3]furan.

Modular synthesis of oligoacetylacetones via site-selective silylation of acetylacetone derivatives.

Oligoacetylacetones consisting of 3,3-disubstituted pentane-2,4-diones were synthesized through a terminal silylation and oxidative coupling protocol. Highly selective formation of mono-enol silyl ethers of 3,3-disubstituted acetylacetones was achieved using 1,8-diazabicyclo[5.4.

Splitting and reorientation of π-conjugation by an unprecedented photo-rearrangement reaction.

A dodecahexaene analogue cross-conjugated with four carbonyl groups was prepared from an aliphatic tetraketone. Exposure to LED light (>420 nm) led to the splitting of the dodecahexaene conjugation into two hexatriene subunits, connected through a stereogenic carbon atom. The two triene subunits exhibited excitonic coupling in the UV-Vis absorption and CD spectra.

gem-Digold Acetylide Complexes for Catalytic Intermolecular [4 + 2] Cycloaddition: Having Two Gold Centers Is Better for Asymmetric Catalysis.

Gold(I)-catalyzed highly enantioselective intermolecular [4 + 2] cycloaddition is shown with ynones and cyclohexadiene. Various bicyclo[2.2.

Pre-evaluation of metal ions as a catalyst on chemiluminometric sequential injection analysis with luminol-H2O2 system.

Catalytic effect of metal ions on luminol chemiluminescence (CL) was investigated by sequential injection analysis (SIA). The SIA system was set up with two solenoid micropumps, an eight-port selection valve, and a photosensor module with a fountain-type chemiluminescence cell. The SIA system was controlled and the CL signals were collected by a LabVIEW program.