DBU-Mediated Domino Annulation Reaction of 2-Amino-4H-chromen-4-ones and Aromatic Aldehydes for Synthesis of Polysubstituted 3-Hydroxy-5H-chromeno[2,3-b]pyridinones

Hexafluoroisopropanol (HFIP) has been extensively applied in organic synthesis as a versatile reaction media. However, the application of HFIP as an catalyst in organic synthesis has been rarely studied. Presented here, is the example of HFIP‐catalyzed Mannich‐type reaction between quinoxalin‐2(1H)‐ones and difluoroenoxysilanes. The developed protocol tolerates various substituents under mild reaction conditions, providing a divergent approach to the construction of difluoro‐substituted 3,4‐dihydroquinoxalin‐2(1H)‐ones and monofluoroquinoxalin‐2(1H)‐ones in 51–92% yields.

HFIP‐Catalyzed Mannich Reaction: Divergent Synthesis of Difluoro‐Substituted 3,4‐Dihydroquinoxalin‐2(1H)‐ones and Monofluoroquinoxalin‐2(1H)‐ones

Xiong

Zhang

et al. 2023

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.