Copper-Catalyzed Regioselective Imidation of 2-Pyridones.

We demonstrate a ligand- and glovebox-free regioselective direct C(3)-H imidation of 2-pyridones and also benzylic-type imidation of 2-pyridones bearing a methyl substituent employing Cu(OAc)2·H2O as the catalyst and N-fluorobenzenesulfonimide (NFSI) as an imidating reagent. A broad range of imidated 2-pyridone derivatives is made up to excellent yields. The present strategy operates well on a gram scale, and the ensuing product can be readily subjected to mono- and bis-desulfonylation reactions.

Direct Trideuteromethylation of Sulfenate Anions Generated In Situ from ß-Sulfinyl Esters: An Access to Trideuteromethyl Sulfoxides.

Deuterated organic molecules have immense value in the pharmaceutical industry. Here, we present a synthetic strategy for direct trideuteromethylation of sulfenate ions derived in situ from ß-sulfinyl esters in the presence of a base utilizing inexpensive and abundant CD3OTs as the electrophilic trideuteromethylating agent. This protocol provides straightforward access to an array of trideuteromethyl sulfoxides in yields of 75-92% with a high degree of deuteration. The ensuing trideuteromethyl sulfoxide can be readily modified into trideuteromethyl sulfone and sulfoximine.

Palladium-Catalyzed Regioselective C3-Allylic Alkylation of 2-Aryl Imidazopyridines with MBH Carbonates.

Imidazopyridine is an important framework that constitutes several pharmaceutical drugs and biologically active molecules. Herein, we present the palladium-catalyzed regioselective C3-allylic alkylation of 2-aryl imidazopyridines with MBH carbonates. This strategy furnishes a broad spectrum of C3-allylated imidazopyridines, and their structures have been unequivocally established using X-ray analysis. Besides, the reaction can be easily scaled up on a gram scale, and the ensuing product can be smoothly manipulated into synthetically useful entities.

Heteroarylation of Sulfenate Ions In Situ Generated from ß-Sulfinyl Esters under Transition-Metal-Free Conditions.

Heteroaryl sulfoxides are an integral part of several bioactive molecules and pharmaceuticals. We have described a transition-metal-free route for the direct sulfinylation of 2-halobenzothiazoles and 2-halobenzimidazoles using ß-sulfinyl esters as the source of the sulfenate ion in the presence of a Brønsted base such as LiOtBu, and the corresponding heteroaryl sulfoxides were isolated in yields of 30 to 94%. Moreover, we hypothesized a plausible concerted nucleophilic aromatic substitution (cSNAr) pathway for the direct incorporation of sulfinyl functionality into the 2-haloheteroarenes.

Regioselective allenylation and propargylation of various para-quinone methides using alkynyl azaarenes as pronucleophiles.

We have developed Brønsted base-mediated regioselective allenylation and propargylation of various para-quinone methides using unfunctionalized 2-alkynyl azaarenes as pronucleophiles. The appropriate choice of a base provides an opportunity to achieve either an allenylated product or the propargylated product. The use of KOtBu as a Brønsted base promotes the formation of allenylated products, whereas NaN(SiMe3)2 furnishes the propargylated products. Besides, the current strategy is scalable and can be performed on a gram scale.

Palladium-Catalyzed Direct C2-Biarylation of Indoles.

Biaryl and indole units are important structural motifs in several bioactive molecules and functional materials. We have accomplished straightforward access to C2-biarylated indole derivatives through palladium-catalyzed C-H activation strategy with a broad range of substrate scope in yields of 24 to 92%. Besides, the UV/visible absorption and fluorescence properties of the ensuing products were explored. The calculated higher dihedral angle and rotational barrier values for the selected C2-biarylated indoles show that these compounds may display atropisomerism at room temperature.

Base-promoted 1,6-conjugate addition of alkylazaarenes to para-quinone methides.

1,1,2-Triarylethanes embedded with an azaarene unit were prepared in a single step at ambient temperature via the sodium hexamethyldisilazide mediated 1,6-conjugate addition of unactivated alkylazaarenes on para-quinone methides (p-QMs). The extent of this methodology was investigated with a wide range of p-QMs and alkylazaarenes, and the respective products were obtained in moderate to excellent yields. The regioselective 1,6-conjugate addition of the trialkylazaarene precursor on para-quinone methide was also presented. Besides, we showcased the direct synthesis of the 1,1,2-triarylethane derivative from aldehyde via the in situ generation of para-quinone methide.