Photocatalyst-free hypervalent iodine reagent catalyzed decarboxylative acylarylation of acrylamides with α-oxocarboxylic acids driven by visible-light irradiation

Abstract

A hypervalent iodine(iii) reagent catalyzed carbonylarylation of acrylamides with α-oxocarboxylic acids driven by visible-light without a photoredox catalyst has been developed. The reactions generate the corresponding products in good yields at room temperature. Experiments indicate that a blue LED (450-455 nm) is the most effective energy for the cleavage of the oxygen-iodine bond to initiate the reaction. Mechanistic studies further demonstrate that the reaction undergoes a cascade decarboxylative radical addition/cyclization process along with releasing CO2 and H2.

Visible‐Light‐Mediated Stereoselective 1,2‐Iodoalkylation of Alkynes

“…Atom transfer radical addition (ATRA) of haloalkanes to alkenes and alkynes serves as an atom-economical method of simultaneously forming CÀC and CÀX bonds, and it has been recognized as a useful tool in organic chemistry. [1][2][3] Besides, these methods constantly employed harsh conditions and lack broad functional group tolerance. By using light irradiation, the radical process could be initiated via a direct energy transfer, [5n-p] otherwise, a photocatalyst was always required to activate the reactants which were not able to absorb the visible light (Scheme 1, Equation (a)).…”

“…On the other hand, there are relatively fewer examples of an organic transformation driven by visible-light without a photocatalyst. [2] Currently reported visible-light-induced organic reactions in the absence of photocatalysts deeply relied on the formation of electron-donor-acceptor (EDA) complex. [3] Thus, the development of effective photocatalyst-free transformations with substrates that were not capable of forming EDA complex is a challenging goal in organic synthesis but yet remains largely unexplored.…”

“…By using light irradiation, the radical process could be initiated via a direct energy transfer, [5n-p] otherwise, a photocatalyst was always required to activate the reactants which were not able to absorb the visible light (Scheme 1, Equation (a)). [1][2][3] Besides, these methods constantly employed harsh conditions and lack broad functional group tolerance. To the best of our knowledge, only a few examples induced by visible light in the absence of photocatalyst/initiator was reported to date (Scheme 1, Equation (b)).…”

Metal‐Free Oxidative Decarboxylative Heteroannulation of Alkynyl Carboxylic Acids with Sulfinates and tert‐Butyl Nitrite toward 2,2‐Disulfonyl‐2H‐Azirines

“…The possible reaction mechanism for this decarboxylative tandem heteroannulation protocol was proposed in Scheme 3 on the basis of the present results and previous reports. [3,[9][10][11][12][13] Initially, the hydrogen atom abstraction from alkynyl carboxylic acid 1 by TBHP or t-BuONO [11] generates the propargyl benzoate radical A. [12] Meanwhile, the reaction of sodium sulfinate 2 with t-BuONO affords the sulfonyl radical, NO radical and t-BuONa.…”

“…[12] Meanwhile, the reaction of sodium sulfinate 2 with t-BuONO affords the sulfonyl radical, NO radical and t-BuONa. [13] Subsequently, addition of the sulfonyl radical across the C � In summary, we have developed a novel practical oxidative radical mediated decarboxylative tandem heteroannulation of alkynyl carboxylic acids with sodium sulfinates and t-BuONO, in which t-BuONO serves as the nitrogen source to allow nitrogenincorporation for accessing sulfonylated 2H-azirines with the formation of two CÀ S bonds, one CÀ N bond and one C=N bond. Preliminary mechanistic studies revealed that the reaction might invove a radical process.…”