Transition Metal-Free sp3 C-H Functionalization of Arylacetic Acids for the Synthesis of 1,3,5-Triazines

Sustainable Synthesis of Substituted 1,3,5-Triazines by [ONO]-Pincer-Supported Nickel(II) Complexes via an Acceptorless Dehydrogenative Coupling Strategy

A facile, cost-effective, and sustainable synthesis of substituted triazines from primary alcohols by newly synthesized nickel pincer-type complexes (1-3) has been described. Herein, we report the synthesis of a set of three well-defined Ni(II) O^N^O pincer-type complexes, structurally characterized by analytical, spectral, and X-ray diffraction techniques. Further, the nickel complexes are explored as efficient catalysts (4 mol %) for the construction of 2,4,6-substituted 1,3,5-triazines from readily available alcohols via an acceptorless dehydrogenative coupling (ADC) strategy. A wide range of substituted triazine derivatives (33 examples) has been synthesized from the coupling of alcohols and benzamidine/guanidine hydrochloride with a maximum isolated yield of 92% under mild conditions, with eco-friendly H2O and H2 gas as the only byproducts. A plausible mechanism has been proposed based on a sequence of control experiments. Interestingly, the short synthesis of the antiulcer drug irsogladine and the large-scale synthesis of 2,4-diphenyl-6-(p-tolyl)-1,3,5-triazine highlight the convenience of the current methodology.

Triazines: Syntheses and Inverse Electron-demand Diels-Alder Reactions

Triazines are an important class of six-membered aromatic heterocycles possessing three nitrogen atoms, resulting in three types of regio-isomers: 1,2,4-triazines (a-triazines), 1,2,3-triazines (v-triazines), and 1,3,5-triazines (s-triazines). Notably, the application of triazines as cyclic aza-dienes in inverse electron-demand Diels-Alder (IEDDA) cycloaddition reactions has been established as a unique and powerful method in N-heterocycle synthesis, natural product preparation, and bioorthogonal chemistry. In this review, we comprehensively summarize the advances in the construction of these triazines via annulation and ring-expansion reactions, especially emphasizing recent developments and challenges. The synthetic transformations of triazines are focused on IEDDA cycloaddition reactions, which have allowed access to a wide scope of heterocycles, including pyridines, carbolines, azepines, pyridazines, pyrazines, and pyrimidines. The utilization of triazine IEDDA reactions as key steps in natural product synthesis is also discussed. More importantly, a particular attention is paid on the bioorthogonal application of triazines in fast click ligation with various strained alkenes and alkynes, which opens a new opportunity for studying biomolecules in chemical biology.

A donor design strategy for triazine-carbazole blue thermally activated delayed fluorescence materials

Enhancing the delayed emission proportion by incorporating bulky substituent at the 1-site of carbazole donors is proved to be effective and practical strategy to improve the EL performance of cyaphenine-carbazole type blue TADF emitters.

Aminomethyl Transfer (Mannich) Reactions Between an O-Triethylsilylated Hemiaminal and Anilines, Rn C6 H5-n NH2 Leading to New Diamines, Triamines, Imines, or 1,3,5-Triazines Dependent upon Substituent R

The reactions of the Mannich reagent Et₃ SiOCH₂ NMe₂ (1) with a variety of anilines (mono-substituted RC₆ H₄ NH₂ , R=H, 4-CN, 4-NO₂ , 4-Ph, 4-Me, 4-MeO, 4-Me₂ N; di-substituted R₂ C₆ H₃ NH₂ , R₂ =3,5-(CH₃ )₂ , 3,5-(CF₃ )₂ ; tri-substituted R₃ C₆ H₂ NH₂ , R₃ =3,5-Me₂ -4-Br and a "super bulky" aniline (Ar*NH₂ ) [Ar*=2,6-bis(diphenylmethyl)-4-tert-butylphenyl]) led to the formation of a range of products dependent upon the substituent. With electron-withdrawing substituents, previously unknown diamines, RC₆ H₄ NH(CH₂ NMe₂ ) [R=CN (2 a), NO₂ (2 b)] and R₂ C₆ H₃ NH(CH₂ NMe₂ ) [R₂ =3,5-(CF₃ )₂ (2 c)] were formed. Further reaction of 2 a, b, c with 1 yielded the corresponding triamines RC₆ H₄ N(CH₂ NMe₂ )₂ (R=CN (3 a), NO₂ (3 b) and R₂ C₆ H₃ N(CH₂ NMe₂ )₂ , R₂ =3,5-(CF₃ )₂ (3 c). The new polyamines were characterized by NMR spectroscopy, and for 2 a, 2 c_, and 3 c, by single crystal XRD. In the case of electron-donating groups, R=4-OMe, 4-NMe₂ , 4-Me, 3,5-Me₂ , 3,5-Me₂ -4-Br, and for R=4-Ph, the reactions with 1 immediately led to the formation of the related 1,3,5-triazines, R=4-MeO (5 a), 4-Me₂ N (5 b), 4-Me (5 c), 3,5-Me₂ (5 d), 3,5-Me₂ -4-Br (5 e), 4-Ph (5 f), 4-Cl (5 g). The "super bulky" aniline rapidly produced a single product, namely the corresponding imine Ar*N=CH₂ (4) which was also characterized by single crystal XRD. Imine 4 is both thermally and oxidatively stable. All reactions are very fast, thus based upon the presence of Si we are tempted to denote the reactions of 1 as examples of "Silick" chemistry.