Katsuyuki Ogura

Palladium(0)/LiCl promoted cross-coupling reaction of (4-pyridyl)stannanes and aromatic bromides: Easy access to poly(4-pyridyl)-substituted aromatics

Abstract A PdCl 2 (PPh 3 ) 2 /LiCl catalyst effectively promoted the cross-coupling reaction of trimethyl(4-pyridyl)stannane and aromatic polybromides to offer easy access to poly(4-pyridyl)-substituted aromatic compounds.

Enantiomeric recognition of alkyl phenyl sulfoxides by crystalline (R)-phenylglycyl-(R)-phenylglycine

Abstract The inclusion compounds of several alkyl phenyl sulfoxides by (R)-phenylglycyl-(R)-phenylglycine [ (R,R)- 1 ] were prepared by two different methods (sorption and crystallization). Alkyl phenyl sulfoxides entered crystalline (R,R)- 1 with high S-enantioselectivity except for methyl phenyl sulfoxide which was recognized with high and reverse enantioselectivity (R-from in 92% ee). From the X-ray crystallographic study of an inclusion compound of bis[(o-methylsulfinyl)benzyl]ether (3) and (R,R)- 1 , it is deduced that the reversal of enantioselectivity was achieved by the conformational change of phenyl groups on the dipeptide layer.

Novel reaction of allylic alcohols with a hexafluoropropene-diethylamine adduct (PPDA) to form α-fluoro-α-(trifluoromethyl)-γ,δ-unsaturated amides

Abstract Treatment of allylic alcohols ( 1 ) with a hexafluoropropene-diethylamine adduct (PPDA) gave α-fluoro-α-(trifluoromethyl)-γ,δ-unsaturated amides ( 2 ), which were shown to be important precursors for synthesizing a variety of fluoro(trifluoromethyl)methylene-containing compounds.

Stereoselective formation of α-fluoro-α-trifluoromethyl-γ-lactones starting from γ-hydroxy-α,β-unsaturated sulfones and a hexafluoropropene-diethylamine adduct (PPDA)

Abstract ( E )-3-Hydroxy-1-alkenyl p -tolyl sulfones ( 1 ) reacted with a hexafluoropropene-diethylamine adduct (PPDA) to afford α-fluoro-α-(trifluoromethyl)-β-[( p -tolylsulfonyl)methyl]-γ-lactones ( 2 ). This reaction is so stereoselective that only one diastereomer of 2 is detected in the reaction mixture. A plausible mechanism for this intriguing reaction is discussed.

Highly stereoselective radical addition to 3-hydroxy-1-(methylthio)-1-(p-tolylsulfonyl)-1-alkenes and its application to the preparation of optically active compounds

Abstract Efficient 1,2-asymmetric induction was realized in the addition of a 1-hydroxyalkyl radical (R2C-OH) to 3-hydroxy-1-(methylthio)-1-(p-tolylsulfonyl)-1-alkenes and their acetates (1): Irradiation of 1 and benzophenone in an alcohol (R2CHOH) gave an adduct (2) with a high syn selectivity. Optically active 1 is easily obtainable by means of Lipase PS-catalyzed transesterification and, therefore, the present radical asymmetric induction provides a synthetic route leading to various chiral compounds.

Asymmetric recognition of 1-arylethylamines by (R)-phenylglycyl-(R)-phenylglycine and its mechanism

Abstract An unprotected dipeptide, ( R )-phenylglycyl-( R )-phenylglycine, which is insoluble in water, was shown to be an excellent resolving reagent for racemic 1-arylethylamines. By simply stirring the mixture of the dipeptide and racemic 1-phenylethylamine in presence of water, asymmetric recognition occurred to give a salt of ( S )-1-phenylethylamine (95% ee) and the dipeptide. X-Ray crystallographic study of the salt elucidated the crystal structure of the diastereomeric salt, where hydrogen bonding and hydrophobic interaction between the dipeptide and amines play important roles in the construction of layers.