Iridium-Catalyzed Transfer Hydrogenation for Construction of Quinolines from 2-Aminobenzyl Alcohols with Enones in Water

Abstract

Herein, we describe a method for the synthesis of functionalized quinolines from 2-aminobenzyl alcohols with α, β-unsaturated ketones. This method exhibits various functional groups tolerance, high-efficiency, environmentally benign and can be performed on a gram scale. Control experiment suggests this transformation is accomplished by iridium complex-catalyzed transfer hydrogenation, which is then followed by the Friedländer cyclization. The results display the alkali is essential for the high selectivities of this catalytic system.

Cyclometalated iridium complexes-catalyzed acceptorless dehydrogenative coupling reaction: construction of quinoline derivatives and evaluation of their antimicrobial activities

“…Aromatic secondary alcohols substituted with electron-donating groups led to higher chemoselectivities and yields of the products (Table 3, entries 2-5) than the aryl secondary alcohols and aminobenzyl alcohol with electron-withdrawing groups (Table 3, entries 8, 11, 12, 15, 16, 19, 20, 23, and 24). Meanwhile, the heteroaromatic secondary alcohols 2i-n could also be employed in the cyclometalated iridium-catalyzed system obtaining the products 3ai-an with excellent yield and chemoselectivity (Table 3, entries [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. The results showed that the yield and chemoselectivity was higher when the heteroaromatic secondary alcohols and aminobenzyl alcohols have electron-donating groups (Table 3, entries 27, 30, 31, 34, 35, 39, and 42).…”

“…In previous studies [39][40][41][42], we found that cyclometalated iridium catalysts can effectively catalyze the dehydrogenation of alcohols to produce carbonyl compounds and hydrogen gas. Therefore, we used cyclometalated iridium complex (TC-6) to catalyze the ADC reaction of o-aminobenzyl alcohols 1 and aryl/heteroaryl/alkyl secondary alcohols 2 that allowed for the efficient synthesis of a series of quinolines 3 (up to 95% yield and >99:1 selectivity) (Figure 2).…”

Recent Advances in the Use of 2‐Aminobenzyl Alcohols in the Synthesis of Quinolines, Quinazolines and Other N‐Heterocycles

“…Another synthesis of quinolines via the reaction of 2-aminobenzyl alcohols with enones was reported by Luo et al in the same year. [42] The reaction was carried out in the presence of 0.1 mol% of an iridium catalyst and 1.0 equivalent of tBuOK in toluene, and two products of quinoline and tetrahydroquinoline were obtained with a relatively ratio of 99:1 in most cases.…”

Synthesis of unsymmetrically tetrasubstituted pyrroles and studies of AIEE in pyrrolo[1,2-a]pyrimidine derivatives

“…On the basis of the widely used synthesis of commercially available chalcones, 13 we have developed an efficient method for the synthesis of polysubstituted NH-pyrroles directly from α,β-unsaturated sulfonimines, which have been shown by Loh, 14 Smith, 15 and Yoshikai 16 to be good precursors for the construction of multisubstituted pyridines (Fig. 1b).…”