Fast regioselective sulfonylation of pyridine/quinoline N-oxides induced by iodine

Abstract

Fast sulfonylation of pyridine/quinoline N-oxides induced by iodine is demonstrated herein. The regioselective protocol occurs under metal-free conditions in a short reaction time (10 min), exhibiting high efficiency (up to 92% yield) and good compatibility (up to 33 examples). A gram-scale reaction was conducted with only a slight loss of production.

Iodine‐Triggered Aerobic Oxysulfonylation of Styrenes

“…Control experiments were performed to understand the mechanism of the iodine‐catalyzed, oxysulfonylation reaction (Figure and Figure 4). Under aerobic conditions and at 1 atm, a near quantitative yield of 3aa was obtained from styrene 1a and tosyl hydrazide 2a .…”

Sulfonyl Hydrazides in Organic Synthesis: A Review of Recent Studies

“…Indole derivatives were not amendable to this procedure. Xiang and He respectively depicted the sulfonylation of heteroaromatic N‐oxides, which might use hypoiodites (generated in situ from [I] and oxidant) as a means of substrate activators. The I 2 /H 2 O 2 ‐promoted protocol accomplished in a short reaction time (10 minutes) and still worked in a gram‐scale (Scheme ).…”

Metal‐free Deoxygenative 2‐Amidation of Quinoline N‐oxides with Nitriles via a Radical Activation Pathway

“…Subsequently, the effect of reaction media on the efficiency was surveyed. It was found that 1,2-dibromoethane (DBE) was the most suitable solvent for the present reaction, while other solvents gave lower yields or trace amount of 3 aa (entries [8][9][10][11][12][13]. To our delight, the desired 3 aa was formed in 91% yield without DBE but under otherwise optimal conditions (entry 14).…”

“…Minisci-type radical addition [4] (Scheme 1b) pathway under metal-free conditions represents a highly attractive approach because of excellent regioselectivity and high efficiency. However, compared with the wellestablished functionalization of quinoline N-oxides activated by various electrophiles (sulfonyl chlorides, [5] acyl chlorides, [6] anhydrides, [7] PyBroP, [8] H-phosphonate, [9] iodine reagents, [10] boron reagents, [11] etc. [12] ), the regioselective nucleophilic substitution of Noxides activated by a free radical activator have not been reported.…”