Difluorphos

SYNPHOS AND DIFLUORPHOS AS LIGANDS FOR RUTHENIUM-CATALYZED HYDROGENATION OF ALKENES AND KETONES... 

Ruthenium(II) complexes bearing atropisomeric diphosphine ligands have proved to be efficient systems for the hydrogenation of a wide range of prochiral substrates. A new catalytic system has been developed based on ruthenium complexes having SYNPHOS and DIFLUORPHOS as chiral diphosphanes (Figure 3.6). 

SYNTHESIS OF IN SITU GENERATED [RuBr2((5)-SYNPHOS)] AND [RuBr2((S)-DIFLUORPHOS)]... 

Table 3.7 Asymmetric ruthenium-catalyzed hydrogenations using SYNPHOS-Ru(II) and DIFLUORPHOS-Ru(II) catalysts.

DIFLUORPHOS (117b) has been prepared by the same chemistry shown in Scheme 12.43 with similar yields, with the exception that the resolution of rac-7b had failed with DBTA. Resolution could only be performed by chiral preparative HPLC.145146... 

The group of Yamamoto reported the catalytic enantioselective hetero-Diels-Alder reactions of azo compound 209 and dienes 208 (Scheme 2.54).87 In a ligand screening the use of BINAP (87) gave higher conversion and enantioselectivity than both Segphos (211) and Difluorphos (212). Interestingly, the optimal silver... 

The allylation reaction between ketones and allylsilanes was achieved in 2005. Yamamoto and Wadamoto developed the asymmetric allylation reaction in the presence of AgF-Difluorphos (Scheme 9.6).12 The reaction of ketones and allyltrimethoxysilane in the presence of AgF and Difluorophos afforded the corresponding tertiary homoallyhc alcohols with high enantioselectivities. Additionally, a,(3-unsaturated ketones could be used as substrates, and this catalytic system could be applied for the asymmetric crotylation reaction to obtain anti adducts preferentially (Schemes 9.7 and 9.8). When a,p-unsaturated ketones were used as substrates, 1,2-addition products were obtained exclusively. As described before, the anti adducts were obtained predominately, regardless of the geometry of crotyltrimethoxysilane. 

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