2,2,2-Trifluoroethoxy Aromatic Heterocycles: Hydrolytically Stable Alternatives to Heteroaryl Chlorides

Functional Hexafluoroisopropyl Group Used in the Construction of Biologically Important Pyrimidine Derivatives

A series of versatile 4-((1,1,1,3,3,3-hexafluoropropan-2-yl)oxy)pyridine intermediates have been developed to efficiently produce biaryls, amines, ethers, and thioethers. These hydrolysis-stable ether intermediates exhibit reactivity toward electron-donating groups and nucleophiles in cross-coupling and nucleophilic substitution reactions while surpassing the stability of corresponding aryl halides. In comparison to conventional coupling methods, this protocol offers an alternative pathway for accessing natural product and drug-like compounds without the need for metal catalysts. With assistance of this approach, we successfully obtained a potent P-glycoprotein inhibitor 4k (YS-370), a potent epidermal growth factor receptor inhibitor 4l (YS-363), and a promising lysine-specific demethylase 1 inhibitor 5g.

Selectfluor-Mediated Regioselective C-3 Alkoxylation, Amination, Sulfenylation, and Selenylation of Quinoxalin-2(1H)-ones

A Selectfluor-promoted oxidative coupling of quinoxalin-2(1H)-ones with alcohols, amines, thiols, and selenols leading to the formation of C-O, C-N, C-S, and C-Se bonds has been developed. The protocol provided good to excellent (53-95%) yields of a wide range of quinoxalin-2(1H)-ones decorated with alkoxy, alkylamino, alkylthio, and arylselenyl groups at the C3-position under metal- and photocatalyst-free conditions. The reaction is believed to proceed through a radical pathway. A broad substrate scope including bioactive molecules, mild reaction conditions, readily available coupling partners, high yields, scalability, step-economy, and metal- and photocatalyst-free conditions are the highlighting features of the method. The synthetic utility of the developed protocol was demonstrated by gram-scale synthesis, C3-alkoxylation of quinoxaline-2(1H)-one with natural alcohols, and synthesis of aldose reductase (ALR2) inhibitor and histamine-4 receptor antagonist in good yields.

Base-catalyzed aryl halide isomerization enables the 4-selective substitution of 3-bromopyridines

The base-catalyzed isomerization of simple aryl halides is presented and utilized to achieve the 4-selective etherification, hydroxylation and amination of 3-bromopyridines. Mechanistic studies support isomerization of 3-bromopyridines to 4-bromopyridines proceeds via pyridyne intermediates and that 4-substitution selectivity is driven by a facile aromatic substitution reaction. Useful features of a tandem aryl halide isomerization/selective interception approach to aromatic functionalization are demonstrated. Example benefits include the use of readily available and stable 3-bromopyridines in place of less available and stable 4-halogenated congeners and the ability to converge mixtures of 3- and 5-bromopyridines to a single 4-substituted product.