Stabilization of Near Identical Hydrogen Bonded Octameric Water Clusters in Crystal Structures of Three Distinct Non-Charged Polyamide Macrocyclic Host Molecules

In this paper, we present a comparative analysis of the solid state structures of three well-resolved hydrates of macrocyclic host molecules 1a, 1b, and 2 containing an intrannular amide-aryl substituent (lariat arm) connected to a fixed 26-membered ring in a normal (-NHCOAr, hosts 1a and 1b) or reverse manner (-CONHAr, host 2). Despite different chemical structures, these hosts crystallize as isostructural tetrahydrates in the same P-1 space group. Moreover, their crystals exhibit identical hydrogen bond motifs resulting in a stabilization of an almost identical unusual octameric water cluster built from the cyclic tetramer core and four water molecules, attached sequentially in an “up-and-down” manner. Further analysis reveals that, among the series, the structure of host 2 provides the most suitable environment for the accommodation of this type of water cluster.

Enhanced Synthesis of oxo-Verdazyl Radicals Bearing Sterically-and Electronically-Diverse C3-Substitents

The synthetic viability of the hydrazine- and phosgene-free synthesis of 1,5-dimethyl oxo-verdazyl radicals has been improved via a detailed study investigating the influence of the aryl substituent on the tetrazinanone...

Carbene-Catalyzed Enantioselective Annulation of Dinucleophilic Hydrazones and Bromoenals for Access to Aryl-Dihydropyridazinones and Related Drugs

4,5-Dihydropyridazinones bearing an aryl substituent at the C6-position are important motifs in drug molecules. Herein, we developed an efficient protocol to access aryl-dihydropyridazinone molecules via a carbene-catalyzed asymmetric annulation between...

Enantioselective N-heterocyclic carbene-catalysed intermolecular crossed benzoin condensations: improved catalyst design and the role of in situ racemisation

A N-heterocyclic carbene catalyst incorporating a bulky yet electron-deficient N-aryl substituent promotes chemoselective and enantioselective intermolecular crossed benzoin condensations.

N-Heterocyclic Carbene Triazolium Salts Containing Brominated Aromatic Motifs: Features and Synthetic Protocol

In this work, we provide a brief overview of the role of N-aryl substituents on triazolium N-heterocyclic carbene (NHC) catalysis. This synopsis provides context for the disclosed synthetic protocol for new chiral N-heterocyclic carbene (NHC) triazolium salts with brominated aromatic motifs. Incorporating brominated aryl rings into NHC structures is challenging, probably due to the substantial steric and electronic influence these substituents exert throughout the synthetic protocol. However, these exact characteristics make it an interesting N-aryl substituent, because the electronic and steric diversity it offers could find broad use in organometallic- and organo-catalysis. Following the synthetic reaction by NMR guided the extensive modification of a known protocol to enable the preparation of these challenging NHC pre-catalysts.

Synthesis and Spectral Study of a New Family of 2,5-Diaryltriazoles Having Restricted Rotation of the 5-Aryl Substituent

Efficient synthesis of 2,5-diaryl substituted 4-azido-1,2,3-triazoles by the reaction of sodium azide with dichlorosubstituted diazadienes was demonstrated. The optical properties of the prepared azidotriazoles were studied to reveal a luminescence maximum in the 360–420 nm region. To improve the luminescence quantum yields a family of 4-azido-1,2,3-triazoles bearing ortho-propargyloxy substituents in the 5 position was prepared. Subsequent intramolecular thermal cyclization permits to construct additional triazole fragment and obtain unique benzoxazocine derivatives condensed with two triazole rings. This new family of condensed heterocycles has a flattened heterocyclic system structure to provide more conjugation of the 5-aryl fragment with the triazole core. As a result, a new type of UV/“blue light-emitting” materials with better photophysical properties was obtained.

Synthesis of amphiphilic asymmetrical dithienylethenes with aryl groups at the reactive carbons

A synthetic route for the preparation of amphiphilic asymmetrical dithienylethenes that incorporate methyl groups at the 4- and 4′-positions and an aryl group at one of the reactive carbons has been developed. The presence of a bulky aryl substituent ensures a relatively large change in molecular geometry upon photoisomerization, whereas the presence of methyl groups provide enhanced photostability. Notably, a substituent effect was systematically revealed en route to the preparation of the dithienylethene precursors. In particular, this formal substitution reaction was significantly inhibited due to steric hindrance, stemming from the presence of aryl and methyl groups at the alpha positions of the preformed thienyl carbanionic carbon, and an aryl group on the monosubstituted perfluorocyclopentene derivative.