Reaction of 3‐(1‐Arylsulfonylalkyl)‐indoles with Easily Enolisable Derivatives Promoted by Potassium Fluoride on Basic Alumina

Abstract

Active methylene compounds and nitro derivatives react with 3-(1-arylsulfonylalkyl)-indoles in the presence of potassium fluoride on basic alumina at room temperature leading to the corresponding adducts in good yields. Under basic conditions, sulfonylindoles suffer elimination of arenesulfinic acid leading to an intermediate vinylogous imine that promptly adds stabilized carbanions. The obtained 3-indolyl derivatives are pivotal intermediates for the synthesis of indole-based alkaloids and amino acids.

YCl3-Catalyzed Highly Selective Ring Opening of Epoxides by Amines at Room Temperature and under Solvent-Free Conditions

“…We also investigated the preparation of β-amino alcohols from a cyclic epoxide, cyclohexene oxide (1d) using 2a as nucleophilic amine; the corresponding reaction gave full conversion of 1d ( Table 2, entry 9). The reaction of 1a with indole (2e), a very commonly studied heterocyclic amine due to its structural features and biological importance [39][40][41][42][43][44], gave only a 30% conversion of 1a (Table 2, entry 5) but, interestingly, 91% regioselectivity (Table 2, entry 10). Since the most reactive position of 2e is C3, the C3-attack is favored to give 3ae and 4ae.…”

Sulfonyl Azoles in the Synthesis of 3-Functionalized Azole Derivatives

“…The pronounced acidity of the hydrogen atoms located between the carbonyl groups makes the corresponding enolate anion very easy to generate using basic reagents of modest strength. As a matter of fact, KF on basic alumina is the best promoter for the addition of a series of malonic acid derivatives to sulfonyl indoles (Scheme ) 64. Curiously, not only are stronger basic systems unnecessary for the described process, but, as an example, the same reaction carried out using NaH in THF gives reduced yields of related adducts.…”

A Two‐Step Synthesis of Unsymmetrical 1,4‐Disubstituted Carbazoles from Sulfonylindoles Under Heterogeneous Catalysis

“…[13] Particularly, these sulfonyl derivatives may react with nitroalkanes, in the presence of a basic promoter, leading to the corresponding 3-(2-nitroalkyl)indoles. [14] Although a large variety of functionalized nitroalkanes successfully react with sulfonylindoles 6, bnitro ketones 2 (EWG = NO 2 , R 2 = Me, Et) gave disappointing results in the same reaction under different solvent/base combinations. The failure is probably ascribable to a preliminary retro-Michael reaction suffered by b-nitro ketones under basic conditions which leads to a decomposition of the nitro derivative.…”