[Acid-base catalysis of chiral Pd complexes: development of novel asymmetric reactions].
Using a unique character of the chiral palladium complexes 1 and 2, several types of novel catalytic asymmetric reactions have been developed. In contrast to the conventional Pd(0)-catalyzed reactions, these complexes function as an acid-base catalyst. Thus active methine compounds were activated to form chiral palladium enolates, which underwent the enantioselective Michael reaction and Mannich-type reaction with up to 99% ee. Interestingly, these palladium enolates acted cooperatively with a strong protic acid activating the electrophiles, formed concomitantly during the formation of the enolates, whereby the C-C bond-forming reaction was promoted. In addition, this palladium enolate chemistry was also applicable to the electrophilic asymmetric fluorination reactions, and thus various carbonyl compounds including beta-ketoesters, beta-ketophosphonates, and oxindoles were fluorinated in a highly enantioselective manner (up to 98% ee). It is advantageous that these reactions were carried out in environmentally friendly alcoholic solvents such as ethanol, and exclusion of air and moisture is not necessary.
Hamashima
Yoshitaka
Y
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan. yhamashi@tagen.tohoku.ac.jp
D000143:Acids; D002384:Catalysis; D002625:Chemistry, Organic; D004952:Esters / Q000737:chemistry; D000431:Ethanol; D005461:Fluorine / Q000737:chemistry; D007211:Indoles / Q000737:chemistry; D055601:Organic Chemistry Phenomena; D009942:Organometallic Compounds / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D012997:Solvents; D013237:Stereoisomerism
D000143:Acids; D004952:Esters; D007211:Indoles; D009942:Organometallic Compounds; D012997:Solvents; D005461:Fluorine; D000431:Ethanol; D010165:Palladium