52604-15-6Relevant articles and documents
An Efficient Route to Highly Substituted Indoles via Tetrahydroindol-4(5H)-one Intermediates Produced by Ring-Opening Cyclization of Spirocyclopropanes with Amines
Nambu, Hisanori,Hirota, Wataru,Fukumoto, Masahiro,Tamura, Takafumi,Yakura, Takayuki
, p. 16799 - 16805 (2017)
An efficient route to highly substituted indoles was developed. It included regioselective functionalization of tetrahydroindol-4(5H)-ones, prepared by ring-opening cyclization of cyclohexane-1,3-dione-2-spirocyclopropanes with primary amines, and subsequent oxidation. The 6-substituted indoles were synthesized from a readily available 5-substituted cyclohexane-1,3-dione-2-spirocyclopropane. The synthesis of 5- and 7-substituted indoles was achieved by regioselective electrophilic alkylation of tetrahydroindol-4(5H)-one, followed by oxidation. The 4-substituted indoles were synthesized by nucleophilic alkylation of the corresponding pyrrole derivative, which was prepared by partial oxidation of tetrahydroindol-4(5H)-one, and sequential oxidation. The synthesis of 4-substituted indoles was also accomplished by palladium-catalyzed coupling of 4-hydroxyindole-derived triflates. Furthermore, the synthesis of 4,5,6,7-tetrasubstituted indoles was achieved by using these regioselective alkylations.
Iron-Catalyzed Reductive Cyclization by Hydromagnesiation: A Modular Strategy Towards N-Heterocycles
Larin, Egor M.,Lautens, Mark,Loup, Joachim
, p. 22345 - 22351 (2021/09/09)
A reductive cyclization to prepare a variety of N-heterocycles, through the use of ortho-vinylanilides, is reported. The reaction is catalyzed by an inexpensive and bench-stable iron complex and generally occurs at ambient temperature. The transformation likely proceeds through hydromagnesiation of the vinyl group, and trapping of the in situ generated benzylic anion by an intramolecular electrophile to form the heterocycle. This iron-catalyzed strategy was shown to be broadly applicable and was utilized in the synthesis of substituted indoles, oxindoles and tetrahydrobenzoazepinoindolone derivatives. Mechanistic studies indicated that the reversibility of the hydride transfer step depends on the reactivity of the tethered electrophile. The synthetic utility of our approach was further demonstrated by the formal synthesis of a reported bioactive compound and a family of natural products.
Room-Temperature Palladium(II)-Catalyzed Direct 2-Arylation of Indoles with Tetraarylstannanes
Liu, Yuxia,Wang, Chao,Huang, Linjuan,Xue, Dong
supporting information, p. 1613 - 1618 (2020/09/15)
A palladium(II)-catalyzed direct 2-arylation of indoles by tetraarylstannanes with oxygen (balloon) as the oxidant at room temperature has been developed. Various tetraarylstannanes can be employed as aryl sources for 2-arylation of indoles in up to 89% yield, providing a practical and efficient catalytic protocol for accessing 2-arylindoles.
Mechanochemical Pd(II)-Catalyzed Direct and C-2-Selective Arylation of Indoles
Das, Dharmendra,Bhutia, Zigmee T.,Chatterjee, Amrita,Banerjee, Mainak
, p. 10764 - 10774 (2019/09/09)
A mechanochemical method for the preparation of synthetically useful 2-arylindoles is developed using Pd(II) as the catalyst in the absence of phosphine ligands in a ball-mill. The developed protocol is highly C-2 selective and tolerant of structural variations with electron-rich and electron-deficient substituents both in indoles and iodoarenes. Arylation is possible in both unprotected indoles and N-protected indoles with the electron-donating group with the former substrate being relatively slower to react and little less yielding. Indoles with a deactivated five-membered ring could also take part in the reaction with ease. The scalability of the reaction was demonstrated by conducting the reaction in the gram scale. In general, the reactions were achieved in a shorter time than the conventional methods.
