Palladium-Catalyzed Asymmetric Allylic Alkylation of α-Aryl Ketones

✍ Scribed by Barry M. Trost; Gretchen M. Schroeder; Jesper Kristensen

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 115 KB
• Volume: 41
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/1521-3773(20020916)41:18<3492::aid-anie3492>3.0.co;2-p

✦ Synopsis

The generation of quatenary chiral centers through catalytic asymmetric alkylation of ketone enolates has been the subject of investigation in recent years. [1] The palladiumcatalyzed asymmetric allylic alkylation (AAA) of prochiral nucleophiles represents one such strategy for the creation of quaternary chiral centers. [2] Given the success of stabilized nucleophiles such as b-ketoesters in palladium-catalyzed AAA [3, 4] we inquired whether simple ketone enolates, perhaps the most important class of nucleophiles, would function. Previously, we reported the AAA of a'-blocked a-alkylcycloalkanones. [3a] Herein we report the palladium-catalyzed AAA of a series of a'-unblocked enolates: aryl ketone enolates.

Initial studies examined the reaction of 2-phenylcyclohexanone (1 a) with allyl acetate (2) using the conditions developed in our previous work with a'-blocked a-alkylcycloalkanones: 2 equivalents of LDA, 1 equivalent of trimethyltin chloride, 2.5 % [(h 3 -C 3 H 5 PdCl) 2 ], and 5 % L ST in DME as solvent [Eq. ( 1)]. Unfortunately, under these standard