Monophosphine CAMP

Early work in asymmetric hydrogenation by Knowles [30] and Horner [31] was accompanied hand in hand by important breakthroughs by Kagan [32] and Knowles [33]. Two ligands feature prominently in this regard the tartrate-derived bidentate ligand DIOP (5, Equation 1) [32] and the chiral monophosphine CAMP (8, Equation 2), which can be prepared by resolution with menthol [33]. 

This achievement was unique in two respects 1) it was the first example of industrial application of a homogeneous enantioselective catalysis methodology and 2) it represented a rare example of very quick convergence of basic knowledge into commercial application. The monophosphine ligand CAMP was shortly replaced by the related diphosphine ligand DIPAMP which improved the selectivity for the I-DOPA system up to 95% ee [45]. 

Some chiral monophosphines were also prepared during the period 1971-1973. Camp (cyclohexyl o-anisyl methyl phosphine) led to a quite high ee (up to 90%) in asymmetric hydrogenation of W-acetyl dehydrophenylalanine [29] and neomenthyl diphenyl phosphine gave modest ee s in the reduction of various conjugated acids [30]. 

---