Modification of Chiral Monodentate Phosphine Ligands (MOP) for Palladium-Catalyzed Asymmetric Hydrosilylation of Cyclic 1,3-Dienes

Preparation of New Ferrocenylmonophosphine Ligands Containing Two Planar Chiral Ferrocenyl Moieties and Their Use for Palladium-Catalyzed Asymmetric Hydrosilylation of 1,3-Dienes

“…For styrene derivatives, 2-(diphenylphosphino)-1,1'-binaphthyl (H-MOP; 2a) [5] and its analog 2b containing the bis[3,5bis(trifluoromethyl)phenyl]phosphino group [6] are more effective than MeO-MOP at giving the hydrosilylation products of over 95% ee. For the asymmetric hydrosilylation of 1,3-dienes, which is a very useful asymmetric transformation because it produces enantiomerically enriched allylic silanes, we found that MOP ligand 2c substituted with a 3,5-dimethyl-4-methoxyphenyl group at the 2' position [7] and its long-chainalkylated version 2d [8] are better than others. The ligand 2d showed 91% ee for the hydrosilylation of cyclopentadiene.…”

“…The hydrosilylation proceeded in a 1,4-fashion to give (Z)-4-(trichlorosilyl)-dec-2-ene (11a) as a major product with over 80% selectivity, together with a minor amount of regioisomers (E)-2-(trichlorosilyl)-dec-3-ene (12a) and (Z)-1-(trichlorosilyl)-dec-2ene (13a), the ratio being slightly dependent on the ligand employed (Entries 1 ± 4 in the Table 1). The enantiomer excess of 11a was measured by HPLC analysis (Chiralcel OD-H) of the homoallyl alcohol 14a [7] obtained by the reaction with benzaldehyde in DMF, which proceeds via a six-membered cyclic transition state [17], and the absolute configuration was determined by correlation with the known hydroxy ester 15 [18]. The highest enantioselectivity (87% ee) was observed with ligand 9d where Ar at the Patom is 3,5-(CF 3 ) 2 C 6 H 3 (Entry 4) an the enantioselectivity decreased in the order 9d (Ar 3,5-(CF 3 The reaction at À 58 with 9d gave the allylsilane (S)-11a of 93% ee (Entry 5).…”

Synthesis of Enantioenriched Allylic Silanes via Nickel-Catalyzed Reductive Cross-Coupling

“…Chiral allylic silanes are most commonly prepared through diastereoselective or stereospecific transformations, 7 which include the Claisen rearrangement of vinyl silanes, 8 bis-silylation of allylic alcohols, 9 silylene insertion of allylic ethers, 10 and the alkenylation of 1,1-silaboronates. 11 In addition, several enantioselective transition metal-catalyzed reactions have been developed, including the hydrosilylation of dienes, 12 the silylboration of allenes 13 , the insertion of metal carbenoids into Si-H bonds, 14 and conjugate addition 15 and allylic substitution 16 reactions. Asymmetric transition metal-catalyzed cross-coupling, in which the critical silicon-bearing C(sp 3 ) stereogenic center is established in the C–C bond forming step, represents an alternative and highly modular approach to chiral allylic silanes.…”

Asymmetric Synthesis of Chiral 1,3‐Disubstituted Allylsilanes via Copper(I)‐Catalyzed 1,4‐Conjugate Silylation of α,β‐Unsaturated Sulfones and Subsequent Julia‐Kocienski Olefination

“…Basically, these strategies are classified into two types, including transformations with organic molecules bearing a pre‐installed silyl group [ 8‐21 ] or introductions of silicon to organic compounds. [ 22‐34 ] In the latter cases, the simultaneous induction of chirality and silicon species under asymmetric catalysis is particularly attractive due to the higher synthetic efficiency. However, most of the reported methodologies were limited to the asymmetric synthesis of chiral allylsilanes without C 3 ‐substituent or specific 1,3‐disubstituted allylsilanes (Scheme 1a).…”