Wübbolt S, Oestreich M. Catalytic Electrophilic C-H Silylation of Pyridines Enabled by Temporary Dearomatization.
Angew Chem Int Ed Engl 2015;
54:15876-9. [PMID:
26593854 DOI:
10.1002/anie.201508181]
[Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 10/15/2015] [Indexed: 11/09/2022]
Abstract
A CH silylation of pyridines that seemingly proceeds through electrophilic aromatic substitution (SE Ar) is reported. Reactions of 2- and 3-substituted pyridines with hydrosilanes in the presence of a catalyst that splits the SiH bond into a hydride and a silicon electrophile yield the corresponding 5-silylated pyridines. This formal silylation of an aromatic CH bond is the result of a three-step sequence, consisting of a pyridine hydrosilylation, a dehydrogenative CH silylation of the intermediate enamine, and a 1,4-dihydropyridine retro-hydrosilylation. The key intermediates were detected by (1) H NMR spectroscopy and prepared through the individual steps. This complex interplay of electrophilic silylation, hydride transfer, and proton abstraction is promoted by a single catalyst.
Collapse