Vinylpyridines as Building Blocks for the Photocatalyzed Synthesis of Alkylpyridines

Abstract

The photocatalyzed addition of several hydrogen donors (ethers, aldehydes, alkanes, amides) onto vinylpyridines was achieved. This approach provided access to alkylpyridines, which are important building blocks for the preparation of compounds with biological activity. The strategy was very simple and straightforward because it required only a small amount of a cheap decatungstate salt as photocatalyst. As an added advantage, the reaction could be performed under sunlight irradiation as well as under flow conditions.

A Lewis Base Catalysis Approach for the Photoredox Activation of Boronic Acids and Esters

“…Interestingly, 2‐ and 4‐vinylpyridines were successfully alkylated at the β‐carbon atom ( 3 am and 3 an ), providing examples of reactions with challenging N‐heteroaromatic compounds 17. These results could be extended to a 2‐pyridyl‐containing 1,1‐disubstituted olefin ( 3 ao ), showcasing the possibility to generate pheniramine analogues and the potential application of the method for antihistaminic drug discovery 18. Finally, flavone natural products can also be alkylated, albeit in lower yield ( 3 aq and 3 ar ).…”

Eosin Y as a Direct Hydrogen‐Atom Transfer Photocatalyst for the Functionalization of C−H Bonds

“…Vinylpyridines can also be utilized as building blocks for alkylation to introduce the biologically important pyridine moiety (40). [12] Substituents including electron-rich or electron-deficient aryl rings (41-43), heterocycles (44, 45), and alkyl chains (46)w ere all tolerated. Diene Michael acceptors could be successfully applied to give 1,4-addition type products (47).…”

Advances in the Synthesis of Imine‐Containing Azaarene Derivatives via Photoredox Catalysis

“…[23] In 2017, Ravelli et al focused on using vinylpyridines as building blocks for the synthesis of alkylpyridines, in which a decatungstate salt {TBADT, (nBu 4 N 4 ) 4 [W 10 O 32 ], λ max = 323 nm} was selected as the HAT-based photocatalyst (Scheme 7B). [21] They first attempted the reactions between 2-, 4-or 3vinylpyridine (12 a-c) and diverse nucleophiles (RH, 22-34). Under the irradiation of x W phosphor-coated lamps (λ IRR centred at 310 nm), the corresponding products were obtained in up to 92 % yield.…”

“…In the works of Ravelli and Wang, aldehydes were used as the precursors of acyl radicals; as a result, carbonyls were introduced into azaarene‐containing molecular architectures. In 2017, Ngai and co‐workers developed a reductive coupling method that provided efficient access to γ‐secondary alcohol/amine‐bearing azaarene derivatives .…”