Ketone enolates transition-metal catalyzed allylic

Ketone and ester enolates have historically proven problematic as nucleophiles for the transition metal-catalyzed allylic alkylation reaction, which can be attributed, at least in part, to their less stabilized and more basic nature. In Hght of these limitations, Tsuji demonstrated the first rhodium-catalyzed allylic alkylation reaction using the trimethly-silyl enol ether derived from cyclohexanone, albeit in modest yield (Eq. 4) [9]. Matsuda and co-workers also examined rhodium-catalyzed allylic alkylation, using trimethylsilyl enol ethers with a wide range of aUyhc carbonates [22]. However, this study was problematic as exemplified by the poor regio- and diastereocontrol, which clearly delineates the limitations in terms of the synthetic utihty of this particular reaction. 

E. Ketone Enolates as Nucleophiles in Transition-metal Catalyzed Allylic... 

Transition Metal-catalyzed Allylic Alkylation. Simple ketone enolates were found to be suitable nucleophiles for palladium-catalyzed allylic alkylations. The palladium-catalyzed asymmetric allylic alkylation of a-aryl ketones will take place in the presence of NaHMDS and allyl acetate to produce the desired a,a-disubstituted ketone derivative in high yields andee (eq 16). ... 

Transition metal catalyzed hydrosilylation of a, -unsaturated ketones and aldehydes (78) proceeds in a 1,4- and/or 1,2-fashion to give enol silyl ethers (79) (or the saturated carbonyl compounds 80 after acidic work-up) and/or allyl silyl ethers (81) (or allyl alcohols 82), respectively (equation 54). Monohydrosilanes combined with a Pt or Rh catalyst prefer 1,4-addition. This reaction is an alternative meth for the preparation of enol silyl ethers (79). Diphenylsilane with [RhCl(PPh3)3] catalyst reduces the car-... 

Several examples of transition metal catalysis for the synthesis of piperidines appeared this year. Palladium catalyzed intramolecular urethane cyclization onto an unactivated allylic alcohol was described as the key step in the stereoselective synthesis of the azasugar 1-deoxymannojirimycin . A new synthetic entry into the 2-azabicyclo[3.3.1]nonane framework was accomplished through a palladium mediated intramolecular coupling of amine tethered vinyl halides and ketone enolates in moderate yields . A palladium catalyzed decarboxylative carbonylation of 5-vinyl... 

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