A mechanochemical method for the preparation of synthetically useful 2-arylindoles is developed using Pd(II) as the catalyst in the absence of phosphine ligands in a ball-mill. The developed protocol is highly C-2 selective and tolerant of structural variations with electron-rich and electron-deficient substituents both in indoles and iodoarenes. Arylation is possible in both unprotected indoles and Nprotected indoles with the electron-donating group with the former substrate being relatively slower to react and little less yielding. Indoles with a deactivated five-membered ring could also take part in the reaction with ease. The scalability of the reaction was demonstrated by conducting the reaction in the gram scale. In general, the reactions were achieved in a shorter time than the conventional methods.

An efficient and environmentally sustainable method for the synthesis of imidazo[1,2- a ]pyridine derivatives by domino A 3 -coupling reaction catalyzed by Cu(II)–ascorbate was developed in aqueous micellar media in the presence of sodium dodecyl sulfate (SDS). The catalyst, a dynamic combination of Cu(II)/Cu(I), was generated in situ in the reaction mixture by mixing CuSO 4 with sodium ascorbate and aided a facile 5- exo -dig cycloisomerization of alkynes with the condensation products of 2-aminopyridines and aldehydes to afford a variety of imidazo[1,2- a ]pyridines in good overall yields. A simple experimental setup, water as the “green” medium, and inexpensive catalyst and auxiliary are some of the merits of this protocol.

A new AIE-based fluorimetric probe (TPE-PMI) has been successfully developed utilizing Gabriel reaction for the selective detection of hydrazine in solid, liquid and vapour phases.

An efficient mechanochemical method for manganese-catalyzed regioselective C−H bond alkenylation of indoles with alkynes is developed. Recently, mechanochemical C−H bond activation has received due attention and the use of low-valent first-row transition metals in C−C cross-coupling via C−H activation under mechanochemical conditions is an additional feather to the cost-effectiveness of such useful synthetic protocols.The present method allows direct C-2 alkenylation of indoles in a mixer mill, employing a commercially available low-valent manganese catalyst, MnBr(CO) 5 , providing a sustainable route to hydroindolation on alkynes. The developed protocol is highly C-2-selective by the presence of a heteroaromatic N atom as a directing group (namely, pyridyl) and tolerant of structural variations with electron-rich and electron-deficient substituents both in the indoles and in the alkynes. Silica as the grinding media and the presence of a catalytic amount of acid and DIPEA as the base worked favorably to afford a variety of 2-alkenyl indoles in excellent yields at ambient conditions. The terminal alkynes offered better results than internal alkynes in terms of yields and reactivity. The scalability of the reaction was demonstrated by conducting the reactions in the gram scale. A short study indicated that a little tweak in conditions can be useful for double alkenylation to afford carbazole derivatives in moderate yields. A low E-factor along with a clean reaction profile, an easy experimental setup, the absence of an anhydrous condition, and being devoid of toxic organic solvents proclaims its advantage over the available conventional methods.

A green and efficient mechanochemical method for the synthesis of a series of 2‐arylimidazo[1,2‐a]pyridines was developed using an electrical grinder. I2 catalyzed mechanochemical grinding facilitates the cyclocondensation reaction between various aryl methyl ketones and 2‐aminopyridines to afford 2‐arylimidazo[1,2‐a]pyridines in good yields at ambient temperature. The method was successfully used for the gram‐scale synthesis of a marketed drug, zolimidine. The noticeable advantages of this environmentally sustainable protocol include mild conditions, simple instrumentation, inexpensive catalyst, atom economy, short reaction time etc.