Facile Preparation of Benzo[4,5]thieno[2,3-b]pyridines and Naphtho[b-4,5]thieno[2,3-b]pyridines via the Reaction of Barton Esters and Benzynes

Abstract

Titled compounds were prepared in a one-pot synthesis by generating symmetrically substituted benzyne intermediates by the diazotization of anthranilic acids in the presence of Barton esters. Unsymmetrically substituted aryne either gave mixtures of regioisomers or failed. However, nitro and methyl derivatives of titled compounds could be obtained as single products using appropriately substituted Barton esters.

o-Silylaryl Triflates: A Journey of Kobayashi Aryne Precursors

“…474 In 2002, Biehl et al investigated the reaction between Barton esters and arynes. Following their early study on Barton esters with arynes generated from anthranilic acids, 475 they reported a reaction between acetic acid 2-selenoxo-2H-pyridin-1-yl esters 6-86, namely, Barton 2-selenoxo esters and arynes generated from different precursors (Scheme 88). 476 Among them, the reactions with o-silylaryl triflates could afford benzo[b]seleno [2,3-b]pyridines in moderate yields.…”

Facile synthesis of 4H-naphtho[2,3-e] derivatives of 1,3-thiazines and 1,3-selenazines and naphtho[2',3':4,5] derivatives of selenolo[2,3-b]pyridines and thieno[2,3-b]pyridines via 2,3-didehydronaphthalene

“…These novel results suggested that the reaction of the corresponding selenium and sulfur derivatives, such as Barton esters with arynes under similar conditions, might be worthy of study. Earlier we have reported the 4H-1,3-benzoselenazines10, benzo [4,5]thieno [2,3-b]pyridines 11 and benzo [4,5]selenolo [2,3-b]pyridines 12 by the reaction of various benzynes with the respective selenium, sulfur containing…”

“…The reaction of benzyne (4) with the esters 8 and 10 giving 9 and 11, respectively, probably proceeds by the usual cycloaddition pathway previously reported. 11 However, the reaction of 4 with thiaazabutadienes (2) and with selenoazadienes (6) to give 5 and 7 is worthy of discussion. We 12 have shown that the reaction of selenoazadienes with benzynes generated by the reaction of 2-trimethylsilylphenyl triflates with CsF at room temperature gave extremely polar compounds which LC/MS showed to be N-oxide derivatives.…”

Arynes as Radical Acceptors: TEMPO‐Mediated Cascades Comprising Addition, Cyclization, and Trapping

“…[8a] The low-lying LUMO of arynes should also make them ideal radical acceptors; however, cascades comprising arynes as acceptors are nearly unexplored. [12] The main challenge in such transformations lies in the low concentrations of both aryne and radical, as both reaction components are highly reactive intermediates. [13] Therefore, coupling of a radical with an aryne in a chain reaction is highly challenging and, not surprisingly, only very few aryne radical reactions have been reported, mostly discovered as unexpected processes.…”