Iodine‐Mediated Sulfonylation of Quinoline N‐Oxides: a Mild and Metal‐Free One‐Pot Synthesis of 2‐Sulfonyl Quinolines

Abstract

A synthetic strategy for an iodine‐mediated sulfonylation of quinoline N‐oxides has been developed. A wide variety of 2‐sulfonyl quinoline derivatives were synthesized by reacting various quinoline N‐oxides with different sodium sulfinates in the presence of sub‐stoichiometric amounts of I2 in one pot, after 2 h at room temperature.

Recent Advances in the Synthesis of C2‐Functionalized Pyridines and Quinolines Using N‐Oxide Chemistry

“…Interestingly, Zhao's group found that this reaction could even be performed without TBHP. Moreover, I 2 is an effective activating agent and can be regenerated by air oxidation of the iodide ion produced in the reaction (Scheme 47B) [72] …”

“…Moreover, I 2 is an effective activating agent and can be regenerated by air oxidation of the iodide ion produced in the reaction (Scheme 47B). [72] In 2017, an efficient, ultrasound-accelerated onepot synthesis of 2-sulfonylquinolines in water was developed by He's group (Scheme 48). [73] Ultrasound irradiation aided in the zinc-dust-mediated reduction of the sulfonyl chloride to a zinc bissulfinate compound, group later reported a TsCl-promoted aqueous sulfonylation that proceeds via the traditional Reissert-type mechanism (Scheme 49).…”

A Direct C2‐Selective Phenoxylation and Alkoxylation of Quinoline N‐Oxides with Various Phenols and Alcohols in the Presence of H‐Phosphonate

“…However, this DABCO‐promoted cyclization reaction employs an unstable starting compound, o ‐alkynylaryl isocyanide, which was synthesized through the dehydration of N ‐formylamide by the use of a harsh reagent, POCl 3 , and a large excess of ( i Pr) 2 EtN (8 equiv.). Recently, quinoline N ‐oxides have been well studied in the selective construction of C2–C, C2–N, and C2–S bonds. Comparatively, there are only few reports in the literature concerning the selective construction of C2–O bonds .…”

“…In our previously reports, we described the H ‐phosphonate‐mediated C2‐selective amination, alkylation, and sulfonation of quinoline N ‐oxides towards 2‐substituted quinolines and found that H ‐phosphonate played a key role in the activation of C2–H covalent bonds. [17a], [17b], [18b] Therefore, we continuously committed our efforts to explore our practical methodology for the selective construction of the challenging C2–O bond. Herein, we would like to disclose the highly efficient one‐pot synthetic method for the synthesis of 2‐aroxy(alkoxy)quinolines in the presence of H ‐phosphonate and CCl 4 under mild conditions (Scheme e).…”

Copper-Catalyzed Deoxygenative C2-Sulfonylation of Quinoline N-Oxides with DABSO and Phenyldiazonium Tetrafluoroborates for the Synthesis of 2-Sulfonylquinolines via a Radical Reaction

“…He's group (Scheme 1b) 6 and Zeng's group 7 independently disclosed the reaction of quinoline N-oxides with sulfonyl hydrazides, and a series of the corresponding products was efficiently obtained. In the presence of iodine as catalyst, deoxygenative and regioselective 2-sulfonylation of quinoline N-oxides with sodium sulfinate salts was developed by Zhao's group (Scheme 1c) 8 and Yotphan's group, 9 providing the desired products in moderate to high yield at room temperature. Although various methods for the deoxygenative sulfonylation of quinoline N-oxides have been established, there are few examples providing a method for the direct construction of 2-sulfonylquinolines via a radical pathway.…”