Ruthenium compounds with chiral ligand

The intermediate sulfonimide derived from saccharin by addition of an alkyllithium compound is also the starting material for sultams mimicking the behavior of camphorsultams. The sultams arc readily obtained from, e.g., 3-methylbenzisothiazole 1,1-dioxide, by ruthenium-catalyzed enantioselective reduction, using BINAP as a chiral ligand, in enantiomerically pure form 79. Thus, both enantiomers can be obtained by using the appropriate enantiomer of the control ligand. Like the camphorsultams, the saccharin derivatives readily form amides with carboxylic acids which can be alkylated via the carbanion (Section D.1.1.1.3.1.) or, if unsaturated carboxylic acids are used, may react as chiral dienophiles in Diels—Alder reactions (Section D.l.6.1.1.1.). 

BINAP does not have a chirality center, but nevertheless, it is a chiral compound because the single bond joining the two ring systems does not experience free rotation (as a result of steric hindrance). BINAP can be used as a chiral ligand to form a complex with ruthenium, producing a chiral catalyst capable of achieving very pronounced enandoselectivity ... 

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