An Approach to the Construction of Benzofuran-thieno[3,2-b]indole-Cored N,O,S-Heteroacenes Using Fischer Indolization

Abstract

A series of 6H-benzofuro­[2′,3′:4,5]­thieno­[3,2-b]­indoles were readily synthesized from methyl 3-aminothieno­[3,2-b]­benzofuran-2-carboxylates using a one-pot procedure with Fischer indolization as the key step. At the same time, 3-aminothieno­[3,2-b]­benzofuran-2-carboxylates were prepared from 3-chlorobenzofuran-2-carbaldehydes in three steps, including replacement of the Cl atom at the C-3 position of these starting substrates onto the -SCH2CO2Me moiety, conversion of the CHO group at the C-2 position into the CN group, followed by base-promoted cyclization of the formed carbonitrile. The present route was elaborated by us because we failed to obtain directly the desired 3-aminothiophene-2-carboxylate by reaction of 3-chlorobenzofuran-2-carbonitrile with methyl thioglycolate in the presence of various bases. In turn, 3-chlorobenzofuran-2-carbaldehydes were prepared from benzofuran-3­(2H)-ones following the Vilsmeier–Haack–Arnold reaction.

Facile Access to α-Substituted β-Thio Enals from 1,2,3-Triazines and Thiols

“…13 C NMR (125 MHz, CDCl 3 ):  = 189.8, 155. 4,134.8,128.9,128.8,128.0,126.4,36.8. HRMS (ESI): m/z [M + H] + calcd for C 10 H 11 OS: 179.0525; found: 179.0522.…”

“…-Substituted -thio enals are a class of unique structure that exhibits ubiquitous biological activities (Scheme 1a). [1][2][3][4] However, despite of their importance, the selective preparation of this class of -substituted -thio enals remains challenging, and is accompanied by multistep synthetic procedures. 5 Taking the synthesis of ,-dithio enals as an example, compared with -thiolation, the relatively more difficult -thiolation usually requires catalyst and base mediation.…”

A general approach to construct selenopheno[3,2-b]indole-cored molecules using Fischer indolization

“…Previously, in a series of our works, we have suggested a convenient strategy for the construction of various thieno [3,2-b] indoles and thieno [3,2-b]indole-fused molecules based on the Fischer indole synthesis. 25 In the context of this strategy, the thieno [3,2-b]indole fragment of the desired molecule was constructed by Fischer indolization of the thiophen-3(2H)-one arylhydrazone part in intermediate C, formed in situ by the reaction of thiophen-3(2H)-ones A 26-29 or 3-aminothiophenes B [30][31][32][33][34] with arylhydrazines. In turn, substrates A and B were generated respectively from 3-hydroxy-or 3-aminothiophene-2-carboxylates.…”

Green methodologies for the synthesis of 2-aminothiophene

“…In fact, 2-aminothiophenes continue to raise an interest in both organic synthesis and medicinal chemistry. Interestingly, the synthesis of 2-aminothiophenes is a lot more well known than the synthesis of 3-aminothiophene, mostly because 2-aminothiophenes synthetic routes are, for now, more accessible than 3-aminothiophene (Han et al 2018 ; Novanna et al 2019 ; Batsyts et al 2019 ; Irgashev et al 2021 ). For example, the main strategy to synthesize 3-amiothiophenes is Thorpe–Ziegler cyclization, which often requires precursor synthesis (Dagoneau et al 2019 ).…”