Sequential Knoevenagel [4+1] Cycloaddition–Condensation–Aza-Friedel–Crafts Intramolecular Cyclization: A 4-Center-3-Component Reaction Toward Tunable Fluorescent Indolizine Tetracycles

The visible-light-induced synthesis of 5-phosphoryl-functionalized pyrroles has been established by eosin Y catalysis, and different electron-donating or electron-withdrawing group substituted secondary Hphosphine oxides and phenacylmalononitriles showed good reactivity toward the reaction, affording the cascade phosphinoylation/cyclization products in 82-98% yields via PÀ C/CÀ N annulation. Step-by-step control experiments and 31 P NMR tracking experiments were further performed to gain the insights of the plausible reaction mechanism and kinetic reaction process. This reaction may have implications for the construction of C(sp 2 )À P bonds in organophosphorus chemistry.

Visible‐Light‐Induced Cascade Phosphinoylation/Cyclization of Phenacylmalononitriles with SecondaryH‐phosphine Oxides

Xiong

Shi

et al. 2022

Access to 2‐Sulfonyl‐4‐arylphenols and 2,6‐Bis‐sulfonyl 5‐Aryl‐4‐arylidene‐2‐cyclohexenones via Metal Triflates‐Catalyzed Domino Cyclocondensation of 1,3‐Bis‐sulfonylacetones and 3‐Arylacroleins

Chang,

Hsueh

2023

Herein, metal triflates–catalyzed one‐pot domino cyclocondensation of 1,3‐bis‐sulfonylacetones and 3‐arylacroleins via (3+3) or (3+2+1) annulation has been proposed to construct diversified 2‐sulfonyl‐4‐arylphenols and 2,6‐bis‐sulfonyl 5‐aryl‐4‐arylidene‐2‐cyclohexenones. In this effective reaction, C−C and C=C bonds are formed via a cascade process and 3‐arylacrolein acts as a C3 and C1 synthon during the formation of a six‐membered ring system under mild conditions. A plausible mechanism has been proposed and discussed.

One‐Pot Synthesis of Sulfonylated 5‐Aroyl‐2‐Arylpyridines via Ruthenium‐Catalyzed and K₂S₂O₈‐Mediated Domino Annulation of β‐Ketosulfones with DMF

Chang,

Yang,

Chen

2024

Ruthenium‐catalyzed and K2S2O8‐mediated synthesis of diverse sulfonylated 5‐aroyl‐2‐arylpyridines was developed through one‐pot stepwise annulation of two molecules of β‐ketosulfones and N,N‐dimethylformamide (DMF) under the sealed tube conditions. In the overall process, DMF acts as the synthon of one carbon and one imino moiety in the construction of pyridine skeleton via cascade formation of single (C‐C/C‐N) and double (C=C/C=N) bonds under refluxing DMF conditions. Plausible reaction mechanism is proposed and discussed.