(S)-Phenylalanine-derived chiral phosphorus–olefin ligands in rhodium-catalyzed asymmetric 1,4-addition reactions

Chiral phosphorus–olefins (S)-1, (S)-4, and (S)-5 have been designed and synthesized. These ligands were all synthesized from (S)-phenylalanine derivatives and act as phosphorus–olefin bidentate ligands to rhodium. The coordination face of the olefin can be effectively controlled by the original chirality of (S)-phenylalanine in all cases; the rhodium complexes coordinated with these ligands have been employed as catalysts for the asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated ketones, to give 1,4-adducts with high enantioselectivities for cyclic enones and moderate enantioselectivities for acyclic enones.

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(S)-2-Benzyl-1-(diphenylphosphino)-4-methyl-2,5-dihydro-1H-pyrroleC24H24NP[α]D20=+209 (c 0.52, THF)Absolute configuration: (S)Source of chirality: (S)-Phenylalanine

(S)-2-Benzyl-4-(benzyloxymethyl)-1-(diphenylphosphino)-2,5-dihydro-1H-pyrroleC31H30NOP[α]D25=+187 (c 0.56, THF)Absolute configuration: (S)Source of chirality: (S)-Phenylalanine

(S)-2-Benzyl-1-(diphenylphosphino)-4-phenyl-2,5-dihydro-1H-pyrroleC29H26NP[α]D25=+224 (c 0.53, THF)Absolute configuration: (S)Source of chirality: (S)-Phenylalanine

(S)-6-Benzyl-1-(diphenylphosphino)-4-methyl-1,2,3,6-tetrahydropyridineC25H26NP[α]D30=-41.3 (c 1.00, THF)Absolute configuration: (S)Source of chirality: (S)-Phenylalanine

(S)-2-Benzyl-1-(diphenylphosphino)-3-methyl-2,5-dihydro-1H-pyrroleC24H24NP[α]D20=+209 (c 0.52, THF)Absolute configuration: (S)Source of chirality: (S)-Phenylalanine

(Acetylacetonato)((S)-2-benzyl-1-(diphenylphosphino)-4-methyl-2,5-dihydro-1H-pyrrole)rhodiumC29H31NO2PRh[α]D25=-20.5 (c 0.52, THF)Absolute configuration: (S)Source of chirality: (S)-Phenylalanine

(Acetylacetonato)((S)-6-benzyl-1-(diphenylphosphino)-4-methyl-1,2,3,6-tetrahydropyridine)rhodiumC30H33NO2PRh[α]D20=+69.6 (c 0.58, THF)Absolute configuration: (S)Source of chirality: (S)-Phenylalanine

(Acetylacetonato)((S)-2-benzyl-1-(diphenylphosphino)-3-methyl-2,5-dihydro-1H-pyrrole)rhodiumC29H31NO2PRh[α]D25=+91.6 (c 0.58, THF)Absolute configuration: (S)Source of chirality: (S)-Phenylalanine