Iridium complex-catalyzed allylic alkylation

✍ Scribed by Ryo Takeuchi

• Book ID: 104323684
• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 197 KB
• Volume: 19
• Category: Article
• ISSN: 0277-5387
• DOI: 10.1016/s0277-5387(99)00407-6

✦ Synopsis

An iridium complex was found to be an efficient catalyst for allylic alkylation of allylic acetates with a stabilized carbon nucleophile. Two unique features of iridium complex catalysis are found. (1) Regioselective alkylation at the substituted allylic terminus: the reaction of (E)-2-alkenyl acetates or 1-substituted 2-propenyl acetates with sodium salt of diethyl malonate in the presence of a catalytic amount of [Ir(COD)Cl] 2 /P(OPh) 3 (P/Irs1-2) gave products alkylated at the substituted allylic terminus with 95-99% selectivities. 31 P NMR and 13 C NMR revealed that a catalytically active species is Ir(COD)(P(OPh) 3 )Cl. The p-acceptor property of P(OPh) 3 promotes a carbonium ion character at the substituted allylic terminus. Therefore, the nucleophile is directed to this position. (2) Retention of Z geometry in the allylic alkylation of (Z)-2-alkenyl acetates; the reaction of (Z)-2-alkenyl acetates gave a product alkylated at the unsubstituted allylic terminus with the retention of Z geometry predominantly. Retention of Z geometry in allylic alkylation is also possible by iridium catalysis.