Synthesis of chiral S,N-thioimidazoline ligands for palladium-catalyzed asymmetric allylic alkylations

A series of chiral S,N-thioimidazoline ligands have been synthesized using 2-bromobenzoic acid or 1-bromo-2-naphthoic acid as starting materials. The obtained ligands were evaluated in the Pd-catalyzed asymmetric allylic alkylations and exhibited high catalytic efficiency: yields of up to 94% and enantioselectivities of up to 86% were achieved under the optimized conditions.

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(S)-2-(2-Bromophenyl)-4-isopropyl-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC19H21BrN2[α]D20 = −92 (c 1.22, CH2Cl2)Absolute configuration: (S)

(S)-2-(2-Bromophenyl)-4-phenyl-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC22H19BrN2[α]D20 = −131 (c 1.70, CH2Cl2)Absolute configuration: (S)

(S)-2-(1-Bromonaphthalen-2-yl)-4-(tert-butyl)-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC24H25BrN2[α]D20 = −14 (c 0.19, CHCl3)Absolute configuration: (S)

(S)-4-(tert-Butyl)-2-(2-(phenylthio)phenyl)-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC20H23BrN2[α]D20 = −48 (c 1.10, CH2Cl2)Absolute configuration: (S)

(S)-2-(1-Bromonaphthalen-2-yl)-4-isopropyl-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC23H23BrN2[α]D20 = −49 (c 0.22, CHCl3)Absolute configuration: (S)

(S)-2-(1-Bromonaphthalen-2-yl)-4-phenyl-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC26H21BrN2[α]D20 = −156 (c 0.11, CHCl3)Absolute configuration: (S)

(S)-4-Isopropyl-2-(2-(phenylthio)phenyl)-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC25H26N2S[α]D20 = −37 (c 0.48, CHCl3)Absolute configuration: (S)

(S)-4-Phenyl-2-(2-(phenylthio)phenyl)-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC28H24N2S[α]D20 = −76 (c 0.71, CHCl3)Absolute configuration: (S)

(S)-4-Isopropyl-2-(1-(phenylthio)naphthalen-2-yl)-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC29H28N2S[α]D20 = −4 (c 0.41, CHCl3)Absolute configuration: (S)

(S)-4-Phenyl-2-(1-(phenylthio)naphthalen-2-yl)-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC32H26N2S[α]D20 = −108 (c 0.65, CHCl3)Absolute configuration: (S)

(S)-4-(tert-Butyl)-2-(2-(phenylthio)phenyl)-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC26H28N2S[α]D20 = −18 (c 0.50, CHCl3)Absolute configuration: (S)

(S)-2-(2-(Isopropylthio)phenyl)-4-phenyl-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC25H26N2S[α]D20 = −64 (c 0.1, CH2Cl2)Absolute configuration: (S)

(S)-4-(tert-Butyl)-2-(1-(phenylthio)naphthalen-2-yl)-1-(p-tolyl)-4,5-dihydro-1H-imidazoleC30H30N2S[α]D20 = +31 (c 0.53, CHCl3)Absolute configuration: (S)