Tris(trimethylsilyl)silane and visible-light irradiation: a new metal- and additive-free photochemical process for the synthesis of indoles and oxindoles

Abstract

A combined tris(trimethylsilyl)silane and visible-light-promoted intramolecular reductive cyclization protocol for the synthesis of indoles and oxindoles has been developed. This straightforward and efficient method shows tolerance towards a broad spectrum of functional-groups and enables rapid and practical synthesis of functionalized nitrogen-based heterocycles in high yields under additive and metal-free, mild photochemical conditions.

Silyl Radical Activation of Alkyl Halides in Metallaphotoredox Catalysis: A Unique Pathway for Cross-Electrophile Coupling

“…Notably, entry 6 indicates that the silyl radical is likely not generated via a silane-aryl halide energy-transfer complex as previously proposed. 17 …”

7-Methyl-5-[(4-methylbenzene)sulfonyl]-2H,5H-[1,3]dioxolo[4,5-f]indole: crystal structure and Hirshfeld analysis

“…Not surprisingly, considerable effort is continually being made to develop new and efficient methods for their synthesis. Recently, the development of a useful method for the synthesis of indoles and oxindoles was described (da Silva et al, 2015). The protocol was based on a combination of tris(trimethylsilyl)silane, as the hydride source, and visible light to promote intramolecular reductive cyclization of suitable precursors.…”

Synthesis of Benzothiazoles via Photooxidative Decarboxylation of α‐Keto Acids

“…Afterwards, UV‐Vis experiments suggested the formation of EDA (electron donor‐acceptor) complex between α‐keto acid and 2‐aminothiophenol by clearly shifting the absorption curve of 1 a + 2 a with reference to 1 a and 2 a (Figure ) . The formation of EDA complex was further justified by a change in the physical appearance of the solution of 1 a + 2 a (pale yellow) as compared to that of separate solutions of 1 a and 2 a (colourless) (Figure ).…”

“…In view of the results obtained from control experiments, UV‐Vis studies and literature precedence, the plausible mechanism is given in Scheme . First of all, EDA complex between 1 a and 2 a is formed.…”