MOP-Phen ligands

The most active palladium catalyst system developed for the asymmetric hydrosilylation of cyclopentadiene (Scheme 23) involves the use of the (/ )-MOP-phen ligand (38), which shows significant enhancement of enantioselectivity compared to (R)-MeO-MOP (80% ee from (38), 39% ee from (36a)).114 Other phosphine ligands that afford active palladium catalysts for the same transformation include the /3-7V-sulfonylaminoalkylphosphine (39) and phosphetane ligand (40) (Equation (13)).115-117 A comparison of the enantioselectivities of these ligands for the palladium-catalyzed hydrosilylation of cyclopentadiene is given in Table 8. 

Transpositional reduction of allylic carbonates. Pd-catalyzed Sn2 reduction (HCOOH as hydride donor) of allylic carbonates proceeds enantioselectively in the presence of chiral ligands based on binaphthyl. Chiral allylsilanes are readily available in this manner using an MOP-phen ligand. ... 

Asymmetric hydrogenolysis of allylic esters with formic acid with satisfactory ee was observed[387], Geranyl methyl carbonate (594) was reduced to 570 with formic acid using l,8-bis(dimethylamino)naphthalene as a base and MOP-Phen as the best chiral ligand, achieving 85% ee. 

Significantly better results in addition of non-stabilized nucleophiles have come from hydrogenolysis reactions using formate as a hydride donor as shown in Scheme 8E.46. The racemic cyclic acetate and prochiral linear carbonates were reduced in good enantioselectivities by monophosphine ligands (/ )-MOP (16) and (Zf)-MOP-phen (17), respectively [195]. The chirality of the allylsilane can be efficiently transferred to the carbinol center of the homoallylic alcohol by the subsequent Lewis acid catalyzed carbonyl addition reaction 1196], The analogous... 

In a recent study, a significant improvement was accomplished in the asymmetric palladium-catalyzed 1,4-hydrosilylation of cyclic 1,3-dienes with the use of chiral ligand (/ )-MOP-phen (Scheme 8-2) [18]. Thus hydrosilylation of cyclopentadiene gave 5 in 99% yield with an enantiomeric excess of 80%, which is the highest reported ee value for Pd-catalyzed hydrosilylations of 1,3-dienes. With 1,3-cyclohexadiene, the yield of the... 

Asymmetric hydrogenolysis of allylic carbonates was realized by the use of chiral ligand, (R)-MOP-Phen, with l,8-bis(dimethylamino)naphthalene (NRj) as a base to afford the optically active tenninal olefins (Scheme 7). 

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