Highly efficient [3 + 2] reaction of 3-vinylindoles with 3-indolylmethanols by Brønsted-acid catalysis

Abstract

This paper describes a highly efficient [3 + 2] reaction between 3vinylindoles and 3-indolylmethanols. Novel 2,3-bisindolylmethanes were prepared as single diastereoisomers in high yields with the promotion of 1 mol% 2-hydroxy-3,5-dinitrobenzoic acid.Scheme 1 Our strategy for constructing 2,3 0 -bisindoles.

(5,6‐Dihydro‐1,4‐dithiin‐2‐yl)methanol as a Versatile Allyl‐Cation Equivalent in (3+2) Cycloaddition Reactions

“…To the best of our knowledge, dehydrative heterocyclic‐carbinol (3+2) cycloadditions have so far only been observed in indolecarbinols by Moody and co‐workers, as well as in some follow‐up studies,, including a very recent three‐component reaction reported by Wu and co‐workers . Furthermore, some benzyl alcohols can undergo similar reactions that resemble the classical cationic styrene‐dimerization process, as in the cyclopentannulation of styrenes with quinone methides or benzyl alcohols, as described by Angle et al .…”

Formal Asymmetric Organocatalytic [3+2] Cyclization between Enecarbamates and 3‐Indolylmethanols: Rapid Access to 3‐Aminocyclopenta[b]indoles

“…Among them, the direct inverse electron demand [3+2] cycloaddition of electron rich olefin with alkylideneindolenine intermediates3 generated from indolylarylmethanols under acid conditions have been recognized as one of the most efficient and convergent methods (Scheme ). However, to date, there are only limited successful enantioselective strategies that could realize this direct [3+2] dipolar cycloaddition route 4a–c. In 2014, Guo and co‐workers established a chiral phosphoric acid‐catalyzed formal [3+2] cycloaddition reaction of 3‐indolylarylmethanols and 3‐vinylindole, which could concisely furnish cyclopenta[ b ]indole in one synthetic operation, albeit with moderate selectivity (enantiomeric excess ( ee ) <10 %) 4c.…”

“…However, to date, there are only limited successful enantioselective strategies that could realize this direct [3+2] dipolar cycloaddition route 4a–c. In 2014, Guo and co‐workers established a chiral phosphoric acid‐catalyzed formal [3+2] cycloaddition reaction of 3‐indolylarylmethanols and 3‐vinylindole, which could concisely furnish cyclopenta[ b ]indole in one synthetic operation, albeit with moderate selectivity (enantiomeric excess ( ee ) <10 %) 4c. Subsequent to this, Shi et al.…”

Alkylideneindoleninium Ions and Alkylideneindolenines: Key Intermediates for the Asymmetric Synthesis of 3‐Indolyl Derivatives

“…Guo and co‐workers described a [3+2] reaction between 3‐indolylmethanols 77 and 3‐vinylindoles 78 catalyzed by chiral phosphoric acid 11 f to furnish 2,3‐bisindolylmethanes 79 as single diastereoisomers in high yields, albeit in low enantioselectivity (5–10 % ee ). These results might be rationalized by remote chiral control, that is, the reaction sites are far away from the chiral centers of the catalysts (Scheme ) 26. Mechanistically, the active vinylogous iminium ion I from 77 undergoes Michael addition with 105 to form a new vinylogous iminium ion II , which undergoes an intramolecular Friedel–Crafts reaction to yield the 2,3‐bisindole compounds 79 .…”