Chelation-assisted carbon–carbon bond activation by Rh(I) catalysts

✍ Scribed by Chul-Ho Jun; Choong Woon Moon; Hyuk Lee; Dae-Yon Lee

• Book ID: 104421981
• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 207 KB
• Volume: 189
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/s1381-1169(02)00202-9

✦ Synopsis

Herein described is the chelation-assisted C-C bond activation of unstrained ketones under the co-catalyst system of Rh(PPh 3 ) 3 Cl and 2-amino-3-picoline (1). This reaction is based on the strategy we recently developed in hydroacylation with aldehydes in which 2-aminopyridine derivatives function as chelation-assistant tools. Unstrained ketones having a ␤-hydrogen gave rise to alkyl-exchanged ketones via this C-C bond activation under an excess of external olefins. In the absence of external olefins, cycloheptanone underwent a ring contraction to generate five-and six-membered cyclic ketones. Instead of unstrained ketones, sec-alcohols were also employed as a substrate for this C-C bond activation via hydrogen transfer. The reaction of allylamine derivatives under [Rh(C 8 H 14 ) 2 Cl] 2 and PCy 3 afforded symmetric dialkyl ketones via a series of reaction such as olefin isomerization, C-H bond activation, and C-C bond activation. The key intermediate, the imine derived from 1 was generated from a primary amine through dehydrogenation followed by transimination. Consequently, the Rh(I)-catalyzed C-C bond activation of unstrained ketones and their equivalents was demonstrated by utilizing a chelation-assistance strategy.