Transition-metal free highly selective aerobic oxidation of hindered 2-alkylindoles

Abstract

a b s t r a c tA novel and easy access to highly complex 3-oxoindolin-2-ylidene derivatives from the exposure of Ugiadducts bearing an indolyl moiety in Cs 2 CO 3 /DMF to air is reported. This is the first example of aerobic oxidation of 2-alkylindoles to 3-oxoindolin-2-ylidenes. Some advantages of this method are the use of air as oxygen source, transition metal-free reagents and simple conditions, a multicomponent and one-pot process and highly regio-and stereoselective manner to trans-3-oxoindolin-2-ylidenes.

An efficient and practical approach for the synthesis of indoloquinolines and indolo/pyrroloquinoxalines via a Cu-catalyzed Ugi-C/Ugi-N-arylation sequence

“…In continuation of our research interest on multicomponent reactions and indole/pyrrol chemistry, 5,12,[34][35][36][37][38][39][40][41][42][43][44][45] we focused on the preparation of three different products including indolo/pyrrolo [1,2-a]quinoxaline, 7H-indolo[2,3-c]quinoline, and 14H-indolo [2,3-c] [1,4]oxazino [4,3-a]quinolin-4-one, using the posttransformation of Ugi adducts under a copper catalyst. In the rst step, the Ugi condensation of aromatic aldehydes, anilines, acids, and isocyanides leads to the formation of bis-amides in methanol at room temperature (Table 1).…”

Aerobic Oxidative Functionalization of Indoles

“…[132] Jiao and co-workers established a base-promoted method for the aerobic oxidation and α-hydroxylation of carbonyl compounds with O 2 as the oxygen source. [133] Inspired by this reaction, the aerobic oxidation of 2-alkylindoles under Cs 2 CO 3 /DMF con- ditions was reported by Shiri et al [134] Hence, a novel and easy access to highly complex 3-oxoindolin-2ylidenes was discovered. In this protocol, the Ugi adducts bearing an indolyl moiety was generated in situ to enable a multi-component and one-pot process in a highly regio-and stereoselective manner to give target products (Scheme 59).…”

Highly regio- and diastereoselective synthesis of oxo-1,2,3,4-tetrahydropyrazino[1,2-a]indoles, based on a post-Ugi condensation: joint experimental and computational study

“…We are interested in heterocyclic chemistry [36][37][38][39][40][41][42][43][44][45] and reported the synthesis of several heterocyclic systems via MCRs [46][47][48][49][50][51][52][53]. We have also recently reported the synthesis of various heterocyclic systems via the appropriate post-Ugi-adducts reaction [54][55][56][57][58]. Herein, we wish to report a transition metal-free catalyzed and highly region-and diastereoselective approach towards the synthesis of oxo-1,2,3,4tetrahydropyrazino[1,2-a]indoles.…”