Silver‐Catalyzed Stereoselective Aminosulfonylation of Alkynes

Abstract

As ilver-catalyzed intermolecular aminosulfonylation of terminal alkynes with sodium sulfinates and TMSN 3 is reported. This three-component reaction proceeds through sequential hydroazidation of the terminal alkyne and addition of as ulfonyl radical to the resultant vinyl azide.T he method enables the stereoselective synthesis of aw ide range of bsulfonyl enamines without electron-withdrawing groups on the nitrogen atom. These enamines are found to be suitable for av ariety of further transformations.Alkynes are one of the most common and versatile functional groups in organic synthesis,and catalytic methods that enable their efficient transformation into other useful functionalities are therefore highly appealing in both academic research and industrial applications.[1] Direct difunctionalization reactions of alkynes,c apable of affording tri-and tetrasubstituted alkenes,h ave attracted much attention in recent years.[2] Among these,r adical-based 1,2-difunctionalizations of alkynes offer astraightforward means to construct functionalized alkenes by reaction with both carbon- [3] and heteroatom-centered radicals [4] with excellent step-and atomeconomy.[5] Mechanistically,ac ommon reaction pathway is observed involving initiation of the reaction by radical addition to the alkyne to generate av inyl radical intermediate,w hich is then coupled with another component to form the alkene product ( Figure 1a). However,s uch vinyl radical species are highly reactive and readily undergo hydrofunctionalization by H-atom abstraction, [6] which is as ignificant challenge in developing radical-based alkyne difunctionalization reactions.M oreover,a liphatic alkynes are generally unreactive in these processes,which is most likely due to the lack of a p-conjugation stabilizing effects of intermediate alkyl-substituted vinyl radicals compared to aryl-substituted analogues.[7] Consequently,c onceptually distinct approaches are in high demand. In the last years,t he nitrogenation of alkynes with trimethylsilylazide (TMSN 3 )has attracted much attention, where carbon-carbon triple bond cleavage leads to av ariety of nitrogen-containing molecules.[8] Building from our recent efforts on the activation of alkynes by silver catalysis, [9] we herein report an ew strategy to effect radicalbased difunctionalization of terminal alkynes through an unprecedented hydroazidation/ radical addition cascade (Figure 1b). Thek ey point for this successful transformation is that we discovered amild and efficient approach to generate sulfonyl radical from sodium sulfinate,t hus avoiding the initial competitive radical addition to alkynes.[6] To the best of our knowledge,t his is the first example of intermolecular alkyne aminosulfonylation, [10] resulting in stereoselective synthesis of b-sulfonyl N-unprotected enamines,w hich are useful synthetic intermediates whose applications are currently limited by al ack of practical synthetic methods for their preparation.[11] Moreover,only one report regarding the synthesis of N-unprotected enami...

Blue Light induced Coupling of N-Hydroxysulphonamides: An efficient and green Approach to Access Symmetrical Thiosulfonates

“…We observed that no product formation was occurring in the presence of eosin Y after 12 hours (table 1 entry We were astonished to see that only I2 (Iodine) could bring the desired conversion (Table 1, entry 10), and other catalytic conditions provided the desired product with low reaction yield or no reaction ( Table 1, entries 1-6). Encouraged by these findings, our studies were directed to look at the prospective different molar ratio of iodine and Cs2Co3 (cesium carbonate) with ethanol as a solvent ( Table 1, entry [11][12][13][14], but none of these could match the efficacy of model condition which provided thiosulfonate product 3(a-r) in good yield at room temperature in the presence of blue led light (Table 1, entry 10). To screen the effect of time, the model reaction was undertaken under the prevailing conditions in pressure tube using I2 as a catalyst at varying time duration.…”

“…[12]. Recently, the cross-coupling reaction of sulfonyl hydrazides with thiols (or sodium sulfinates with disulfides) has been developed for the preparation of thiosulfonates with the help of transitional metal catalysts [13], Sodium sulfinates [14] and sulfoxides [15] are also important organosulfur compounds. Alternatively, thiosulfonates can be obtained by thiosulfonate exchange reactions of sulfenamides, by the reaction of potassium thiosulfonates with diaryliodonium salts [16].…”

Synthetic exploration of sulfinyl radicals using sulfinyl sulfones

“…Many methodologies and sulfur sources have been developed to install a variety of sulfur functionalities into organic molecules [11][12][13][14] . Among these, the use of sulfur-centered radicals to access sulfur-containing compounds has attracted considerable attention due to their ease of generation and e ciency of reaction [15][16][17][18][19][20] . However, in contrast to the popularity of sulfonyl and thiyl radicals, the utilization of sul nyl radicals in synthetic chemistry has remained unexplored.…”

“…A single report suggested that their thermal decomposition might proceed via homolytic ssion, generating two distinct sulfur-centered radicals-a sul nyl radical and a sulfonyl radical 34 . As sulfonyl radicals are known to undergo facile addition to π-bonds [17][18][19] , sul nyl sulfones appeared to be well suited for our envisioned strategy. Here we describe the successful generation and use of sul nyl sulfones in radical addition / radical coupling reactions with a wide variety of unsaturated hydrocarbons (Fig.…”

Generation of Sulfonylated Tetrazoles through an Iron-Catalyzed Multicomponent Reaction Involving Sulfur Dioxide

“…Recently, our group described a copper-catalyzed four-component reaction of terminal alkynes, aryldiazonium tetrafluoroborates, DABCO·(SO 2 ) 2 , and potassium halide, giving rising to a range of β-halo alkenylsulfones ( Xiang et al., 2017 ). Inspired by this work and recent advances in the reactions of alkynes with trimethylsilyl azide via a radical process ( Liu et al., 2019b ; Wang et al., 2015 ; Wu et al., 2019 ; Xiong et al., 2019 ; Ning et al., 2017 ), we conceived that the sulfone-containing alkenyl azide intermediates might be accessed through the azidosulfonylation of alkynes with the insertion of sulfur dioxide via a radical process. Driven by the importance of tetrazole chemistry and our continuous interest in the insertion of sulfur dioxide, we envisioned that the incorporation of sulfonyl unit into tetrazoles for the construction of valuable sulfonylated tetrazoles might be beneficial for various biological evaluations.…”