Triazine-Based Cationic Leaving Group: Synergistic Driving Forces for Rapid Formation of Carbocation Species

Temperature-Assisted Generation of Arylmethyl Radicals from Bis(arylmethyl)tin Dichlorides: Efficient Reagents for C s p 3 ${{{\bf C}}_{{{\bf s p}}^{3}}}$ - C s p 2 ${{{\bf C}}_{{{\bf s p}}^{2}}}$ Bond-Forming Reactions

The oxidative-addition reaction between an arylmethyl chloride (RCH₂ Cl; R=1-C₁₀ H₇ , 2,4,6-Me₃ C₆ H₂ , 4-MeC₆ H₄ , 3-MeC₆ H₄ , C₆ H₅ , 4-ClC₆ H₄ ) and tin powder in boiling toluene produces bis(arylmethyl)tin dichlorides, [(RCH₂ )₂ SnCl₂ ] in good yields. At 160 °C in mesitylene bis(1-naphthylmethyl)tin dichloride undergoes Sn-C homolytic cleavage to generate two 1-naphthylmethyl radicals (1-C₁₀ H₇ CH₂ ⋅) which were trapped by TEMPO (C₉ H₈ NO⋅). Subsequently, the radicals (RCH₂ ⋅) produced in this manner were utilized for efficient substitution reactions with electron-rich arenes (R'H; R'=2,4,6-Me₃ C₆ H₂ , 1,2,4,5-Me₄ C₆ H, 1,2,3,4,5-Me₅ C₆ ) to obtain a variety of unsymmetrical diarylmethanes (RR'CH₂ ). The addition of one equivalent of iodine (I₂ ) to the reaction mixture resulted in a significant increase in the yields of coupled products.

Design, Synthesis, and Utility of Defined Molecular Scaffolds

A growing theme in chemistry is the joining of multiple organic molecular building blocks to create functional molecules. Diverse derivatizable structures—here termed “scaffolds” comprised of “hubs”—provide the foundation for systematic covalent organization of a rich variety of building blocks. This review encompasses 30 tri- or tetra-armed molecular hubs (e.g., triazine, lysine, arenes, dyes) that are used directly or in combination to give linear, cyclic, or branched scaffolds. Each scaffold is categorized by graph theory into one of 31 trees to express the molecular connectivity and overall architecture. Rational chemistry with exacting numbers of derivatizable sites is emphasized. The incorporation of water-solubilization motifs, robust or self-immolative linkers, enzymatically cleavable groups and functional appendages affords immense (and often late-stage) diversification of the scaffolds. Altogether, 107 target molecules are reviewed along with 19 syntheses to illustrate the distinctive chemistries for creating and derivatizing scaffolds. The review covers the history of the field up through 2020, briefly touching on statistically derivatized carriers employed in immunology as counterpoints to the rationally assembled and derivatized scaffolds here, although most citations are from the past two decades. The scaffolds are used widely in fields ranging from pure chemistry to artificial photosynthesis and biomedical sciences.

Larvicidal Activity of Cinnamic Acid Derivatives: Investigating Alternative Products for Aedes aegypti L. Control

The mosquito Aedes aegypti transmits the virus that causes dengue, yellow fever, Zika and Chikungunya viruses, and in several regions of the planet represents a vector of great clinical importance. In terms of mortality and morbidity, infections caused by Ae. aegypti are among the most serious arthropod transmitted viral diseases. The present study investigated the larvicidal potential of seventeen cinnamic acid derivatives against fourth stage Ae. aegypti larvae. The larvicide assays were performed using larval mortality rates to determine lethal concentration (LC₅₀). Compounds containing the medium alkyl chains butyl cinnamate (7) and pentyl cinnamate (8) presented excellent larvicidal activity with LC₅₀ values of around 0.21-0.17 mM, respectively. While among the derivatives with aryl substituents, the best LC₅₀ result was 0.55 mM for benzyl cinnamate (13). The tested derivatives were natural compounds and in pharmacology and antiparasitic studies, many have been evaluated using biological models for environmental and toxicological safety. Molecular modeling analyses suggest that the larvicidal activity of these compounds might be due to a multi-target mechanism of action involving inhibition of a carbonic anhydrase (CA), a histone deacetylase (HDAC2), and two sodium-dependent cation-chloride co-transporters (CCC2 e CCC3).

Development of a Storable Triazinone-Based Reagent for O- p-Methoxybenzylation under Mild Heating Conditions

A new triazinone-based reagent for O- p-methoxybenzylation has been developed. In spite of its stability in solid form, this reagent converts a free alcohol into the corresponding p-methoxybenzyl ether with mild heating (50-60 °C) in a solution. High functional group tolerance can be achieved because the reaction does not require the addition of an acidic or basic activator.

Cooperation of the Neutral and the Cationic Leaving Group Pathways in Acid-Catalyzed O-Benzylation of TriBOT

The reaction profile of acid-catalyzed O-benzylation with 2,4,6-tris(benzyloxy)-1,3,5-triazine (TriBOT) was analyzed to study the reaction kinetics. The first-order kinetic constant for the formation of benzyl cation species from N-protonated TriBOT (neutral leaving group pathway) was estimated and compared with that of the model compound for TriBOT. Since rapid consumption of TriBOT in the late stage could not be explained solely by this pathway, cooperation of another reaction mechanism, the cationic leaving group pathway, was proposed to rationalize the rate acceleration.