Theoretical Study of Gold-Catalyzed Cyclization of 2-Alkynyl-N-propargylanilines and Rationalization of Kinetic Experimental Phenomena

• DOI: 10.1021/acs.joc.6b02092
• Publication Date: 2016-09-07T21:26:50Z
• Authors: Yeqing Duan; Yuxia Liu; Siwei Bi; Baoping Ling; Yuan-Ye Jiang; Peng Liu
• Keywords: Indoline; Allene; Propargyl; Limiting

Gold-catalyzed cyclization of 2-alkynyl-N-propargylanilines provides a step-economic method for the construction three-dimensional indolines. In this article, M06 functional density theory was employed to gain deeper insights into reaction mechanism and associated intriguing experimental observations. The found first undergo Au(I)-induced form an indole intermediate, 1,3-propargyl migration, substitution with substrate 2-alkynyl-N-propargylaniline (R1) generate intermediate product P1, allene species. Subsequently, Au(I)-catalyzed conversion P1 final P2, indoline compound, occurs through direct rather than via previously proposed four-membered carbocycle intermediate. Thereafter, water-assisted oxygen heterocycle formation proton transfer product. calculated activation free energies indicate that is 5.9 times slower P2 formation, in accordance fact rate-limiting. Futhermore, phenomenon can be accessed only after almost all R1 converts although rate-limiting rationalized by employing energetic span model. We initial facile highly stable key phenomenon.