Iodine‐Promoted One‐Pot Multicomponent Chemoselective Reaction for C‐C/C‐N and C‐C/C‐S Bond Formation Using Thiols

Tunable Regioselective Allylic Alkylation/Iodination of Imidazoheterocycles in Water

The switchable roles of allylic alcohol and molecular iodine as reagents and catalysts have been demonstrated in the regioselective allylic alkylation and iodination of imidazoheterocycles employing the mixture of allylic alcohol-I2. First, we have explored the catalytic activity of iodine for the allylation of imidazoheterocycles using allylic alcohol in an aqueous medium. The allylation of a library of imidazoheterocycles and other electron-rich heterocycles like indole, pyrazole, 4-hydroxy coumarin, and 6-amino uracil has been achieved by employing this methodology. The efficiency of the I2 catalyst for N-allylation of azoles has also been demonstrated. Next, we have shown that this mixture of allylic alcohol and I2 could be beneficial for the iodination of imidazoheterocycles under room temperature. Mechanistic studies indicate that the activation of allylic alcohol by molecular iodine took place probably through halogen bonding, and NMR studies show that the reaction did not proceed through allylic ether formation.

Regioselective synthesis of indazolo[2,3-a]quinazolines enabled by I2/S-facilitated annulation relay dehydrogenative aromatization of cyclohexanones

A method for concise and efficient synthesis of indazolo[2,3-a]quinazolines has been developed via a sequential annulation of 3-aminoindazoles and dehydrogenative aromatization of cyclohexanones. This high regioselectivity is attributed to the fact that the Mannich reaction is superior to the aldol reaction in this system. It is worth mentioning that this convenient process is successfully extended to 3-aminopyrazoles for assembling another class of medicinally prevalent pyrazolo[1,5-a]quinazolines.

Iodine-Promoted Oxidative Cyclization of Acylated and Alkylated Derivatives from Epoxides toward the Synthesis of Aza Heterocycles

A new method for directly synthesizing acylated and alkylated quinazoline derivatives by the epoxide ring-opening reaction in the presence of I₂/DMSO with 2-aminobenzamide is described herein. The developed mild protocol is efficient and displays a wide variety of functional group tolerance and substrate-controlled high selectivity, and the application of a continuous flow technique allows for faster reaction time and higher yields. Moreover, the robustness of the method is applicable in gram-scale synthesis.