C-2/C-3 Annulation and C-2 Alkylation of Indoles with 2-Alkoxycyclopropanoate Esters

Abstract

Abstract:The annulation reaction between various indoles and 2-alkoxycyclopropanoate esters is reported. Both high efficiency and complete stereochemical control was observed in some cases with this annulation process. A single stereocenter on the cyclopropane controls the diastereoselective formation of up to four new stereocenters. A different reaction course was observed with 3-substituted indole substrates, and an intervening C-3 to C-2-migration process arose that gives synthetically useful C-2 alkylation indole products.

Ring Opening of Donor–Acceptor Cyclopropanes with N-Nucleo­philes

“…[137][138][139][140][141][142][143][144][145] In these cases, the chemoselectivity mainly depends upon the sites where substituents are located in the indole. However, reaction of 3-methyl-1H-indole (N-unsubstituted skatole) with a cyclopropane-1,1-dicarboxylate 1a under harsh conditions resulted in N-alkylation proceeding along with formal (3+2)-cycloaddition and leading to product 164 (Scheme 89).…”

Synthesis of 5-Azaindoles via a Cycloaddition Reaction between Nitriles and Donor−Acceptor Cyclopropanes

“…We have shown previously that other functional groups can react in formal dipolar cycloadditions with DA cyclopropanes, including electron deficient pyridines 9 and indoles. 22 While not intended to be exhaustive, Table 4 shows that the 3,4-cyclopropanopiperidine reacts analogously to afford fused azaindoles very efficiently. The reactions with both 4-cyanopyridine and 2-cyanopyridine gave their respective tetrahydropyridoindolizines (Table 3, entries a and b), and both underwent oxidation with SeO2 to the pyridoindolizine.…”

Indole and its alkyl‐substituted derivatives protect erythrocyte and DNA against radical‐induced oxidation

“…Indole is an important substrate used in organic synthesis [1], and its physiological activity attracts much scientific attention as well [2]. Therefore, many derivatives of indole have been synthesized and their biological activities have been determined by in vivo or in vitro methods [3,4].…”