A Comparative Study of Redox-Active Dithiafulvenyl-Functionalized 1,3,6,8-Tetraphenylpyrene Derivatives

A series of 1,3,6,8-tetraphenylpyrene (TPPy) derivatives substituted with redox-active 1,4-dithiafulvenyl (DTF) groups was synthesized and characterized. The conformational properties of these DTF-TPPys and their TPPy precursors were assessed by X-ray single-crystal and nuclear magnetic resonance analyses. Their electronic and redox properties were examined by ultraviolet-visible absorption, fluorescence, and cyclic voltammetric analyses. The DTF substitution was found to strongly modify the absorption, emission, and electrochemical properties, while detailed effects can be linked to substitution patterns and alkyl side chains attached to the DTF groups. Furthermore, the DTF-TPPy derivatives showed sensitivity to acids; in particular, the vinylic proton of DTF group could undergo efficient proton/deuterium exchange with D₂O in an acidic medium.

One-Pot and Two-Chamber Methodologies for Using Acetylene Surrogates in the Synthesis of Pyridazines and Their D-Labeled Derivatives

Acetylene surrogates are efficient tools in modern organic chemistry with largely unexplored potential in the construction of heterocyclic cores. Two novel synthetic paths to 3,6-disubstituted pyridazines were proposed using readily available acetylene surrogates through flexible C₂ unit installation procedures in a common reaction space mode (one-pot) and distributed reaction space mode (two-chamber): (1) an interaction of 1,2,4,5-tetrazine and its acceptor-functionalized derivatives with a CaC₂ -H₂ O mixture performed in a two-chamber reactor led to the corresponding pyridazines in quantitative yields; (2) [4+2] cycloaddition of 1,2,4,5-tetrazines to benzyl vinyl ether can be considered a universal synthetic path to a wide range of pyridazines. Replacing water with D₂ O and vinyl ether with its trideuterated analog in the developed procedures, a range of 4,5-dideuteropyridazines of 95-99% deuteration degree was synthesized for the first time. Quantum chemical modeling allowed to quantify the substituent effect in both synthetic pathways.

Recent advances in dithiafulvenyl-functionalized organic conjugated materials

This review highlights the recent studies of advanced organic π-conjugated materials that contain 1,4-dithiafulvene (DTF) as a redox-active component.

Computational Mechanistic Analysis of Intramolecular Cycloadditions of the 1,3-Dithiolium Cation with Adjacent Alkene and Allene Functional Groups

In this work, the molecular mechanisms for the intramolecular cycloaddition reactions of the 1,3-dithiolium cation with adjacent alkenyl and allenyl groups were investigated by density functional theory calculations. Transition states for the mechanistic steps were searched, and their connections to corresponding reactive intermediates were validated by the intrinsic reaction coordinate method. Our studies demonstrate that both the alkenyl and allenyl groups can readily react with a neighboring 1,3-dithiolium cation first through a one-step asynchronous [3 + 2] cycloaddition path, with moderate activation energy barriers (ca. 20-30 kcal/mol) to overcome. Subsequent to the intramolecular dithiolium-alkene/allene cycloadditions, the resulting intermediates continue to undergo a series of reactions, including rearrangement, ring opening, and deprotonation to eventually yield the thermodynamically favored products, which carry a fused tricyclic molecular skeleton, 3,8-dihydro-2H-indeno[2,1-b]thiophene. Detailed geometric and energetic properties for all of the stationary points (transition states and intermediates) on the reaction potential surfaces have been calculated and examined. Key transition states and reactive intermediates were subjected to quantum theory of atoms in molecules and natural bonding orbital calculations to elucidate their bonding features and the stabilizing effects arising from orbital interactions. Finally, a comparative study using the continuum solvation model based on the charge density was conducted to evaluate the solvent effects on the intramolecular dithiolium-alkene/allene cycloadditions, which are the rate-limiting steps of the overall reactions. The results show that different organic solvents (polar and nonpolar) do not lead to much variations in the heights of activation energy barriers and hence indicate that solvent effects are actually insignificant on the reactions.