Facile synthesis of 2-arylmethylindoles and 2-vinylic indoles through palladium-catalyzed heteroannulations of 2-(2-propynyl)aniline and 2-(2-propynyl)tosylanilide

Abstract

A facile method for the general synthesis of 2-arylmethylindoles has been developed through the reaction of 2-(2-propynyl)aniline or 2-(2-propynyl)tosylanilide with aryl iodides in the presence of Pd(OAc)2, PPh3, and DBU. 2-(2-Propynyl)tosylanilide is found to be reactive also towards electron deficient alkenes in the presence of Pd(OAc)2 and sodium iodide under an oxygen atmosphere, providing easy access to 2-vinylic indoles which possess exclusive E-stereochemistry in the side chain double bond. Operational simplicity, compatibility of the various functional groups, and ease of product formation are the hallmarks of these methods. A mechanism has been proposed to explain the product formation.

Palladium-catalyzed incorporation of atmospheric CO2: efficient synthesis of functionalized oxazolidinones

“…In situ generated Pd(0) 20 undergoes oxidative addition with aryl iodide present in the reaction media to give [ArPd(dppf)I] ( I ) (Cycle B). In the case of terminal alkynes, and in the presence of a catalytic amount of copper, transmetalation of I with copper acetylide II (Cycle A) delivers Pd–alkynyl intermediate III , which upon reductive elimination produces substituted propargylamine IV , as experimentally confirmed by the results reported in eqn (3A).…”

Synthesis of Indoles via Intermolecular and Intramolecular Cyclization by Using Palladium-Based Catalysts

“…Moreover, the benzene ring with electron-donating substituents afforded bette yields for an electron-withdrawing substitute [217]. the side chain C=C (Scheme 74) [218]. Furthermore, Chowdhury et al synthesized (E)-2arylmethylidene-N-tosylindolines (243) and their respective quinoline derivatives by reacting 1-(2-tosylaminophenyl)prop-2-yn-1-ols (241) and aryl iodides (Ar-I) (242) under Pd catalyzed conditions, i.e., PdCl2/Ph3P as a catalyst, n-Bu4NBr as a phase transfer catalyst, and K2CO3 as a base in solvent DMF.…”

Recent advances in the synthesis of indoles from alkynes and nitrogen sources

“…On the one hand, the reaction of (2-propynyl)anilines with aryl halides, catalyzed by Pd(OAc) 2 , PPh 3 and DBU, led to the direct formation of 2-arylmethylindoles 206 in good yields in a single step (Scheme 167). 194 On the other hand, when (2-aminoaryl)propynols were used as substrates in the reaction with PdCl 2 , PPh 3 , K 2 CO 3 , and n-Bu 4 NBr in DMF, the products obtained were (arylmethylidene)indolinols 207. The hydrogenolysis employing Pd/C and cyclohexene in refluxing ethanol afforded 2-arylmethylindoles 206 in a two-step reaction (Scheme 167).…”