Catalytic CH Bond Addition of Pyridines to Allenes by a Rare-Earth Catalyst

• Published in: Chemistry : a European journal Vol. 21; no. 23; pp. 8394 - 8398
• Main Authors: Song, Guoyong, Wang, Baoli, Nishiura, Masayoshi, Hou, Zhaomin
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.06.2015; WILEY‐VCH Verlag; Wiley
• Subjects: alkenylation; allenes; Bonding; Catalysis; Catalysts; Cationic; Chemistry; Chemistry, Multidisciplinary; CH addition; Derivatives; Physical Sciences; Pyridines; Rare earth metals; Scandium; Science & Technology; ACTIVATION; ALKYL; COMPLEXES; REACTIVITY; scandium; POLYMERIZATION; SELECTIVE ALKENYLATION; ALLYLATIONS; alkenylation; allenes; pyridines; C-H addition; INSERTION REACTIONS; COPOLYMERIZATION; DERIVATIVES; CH addition
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.201501121

The catalytic CH addition of pyridines to allenes has been achieved for the first time by using a half‐sandwich scandium catalyst, thus constituting a straightforward and atom‐economical route for the synthesis of alkenylated pyridine derivatives. The reaction proceeded regio‐ and stereoselectively, affording a new family of alkenylated pyridine compounds which are otherwise difficult to synthesize. A cationic Sc‐η2‐pyridyl species was isolated and confirmed to be a key catalyst species in this transformation. Keep it allene: Half‐sandwich scandium dialkyls combined with a borate compound act as an efficient catalyst for the CH bond addition of pyridines to various terminal allenes, leading to formation of a new family of alkenylated pyridine derivatives in high yields and excellent regio‐ and stereoselectivity. A cationic scandium pyridyl species (see scheme) was isolated and confirmed to be a key active catalyst species.