Development of an axially chiral sp3P/sp3NH/sp2N-combined linear tridentate ligand—fac-selective formation of Ru(II) complexes and application to ketone hydrogenation
A newly developed chiral linear tridentateligand, R-PN(H)N (R=H or Ph), possesses Ph2P and PyCH2NH groups at C(2) and C(2′) positions of the 1,1′-binaphthyl skeleton without or with a C(3)-Ph substituent. The steric effect of C(3)-Ph and the electronic effect of the DMSO co-ligand realize the facial selective generation of fac-RuCl2(Ph-PN(H)N)(dmso) and fac-[Ru(H-PN(H)N)(dmso)3](BF4)2, respectively
Efficient Enantioselective Synthesis of Methyl Esters of α-Unsubstituted β-Hydroxy Acids via Asymmetric Aldol-Type Addition of Chiral Boron Enolates of (Methylthio)acetic Acid to Aldehydes
The aldol-type addition of chiral boron enolates of (methylthio)-acetic acid to various aldehydes gives α-(methylthio)-β-hydroxy acids stereoselectively and with good yields. The desulfenylation of methyl esters of the condensation adducts allows methyl esters of α-unsubstituted β-hydroxy acids to be obtained with high ee. Derivatives of (+)-2- and (+)-3-carene were used as chiral inducers. The enantioselectivity and diastereoselectivity of the aldol-type addition are efficaciously controlled by the SMe group in the α-position of the enolate and by the type of chiral ligand used.
Face off: The rutheniumcomplexes of a new axially chiral PNN ligand (L) are highly efficient in the presence of dimethylsulfoxide (DMSO) for hydrogenation of both functionalized and unfunctionalized tert‐alkyl ketones. DMSO is thought to narrow down the many possible complex stereoisomers into a single facial L/Ru complex, thus enhancing the reactivity, selectivity, and productivity.