Synthesis of P-stereogenic BINAP bissulfide analogues

A synthetic route to BINAP disulfide analogues with chirality on one of the phosphorus atoms was developed. The synthesis of these ligands was achieved by step-wise palladium and nickel-catalysed coupling reactions of the precursor binaphthyl triflate with secondary phosphines and phosphine oxides, respectively. C2-Unsymmeric BINAP bissulfide analogues with the same aryl substituents were also synthesized for the sake of comparison. Preliminary studies of the reduction of these sulfides to the free phosphines are also described.

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(R,R)-2-(Methylphenylthiophosphinyl)-2′-(diphenylthiophosphinyl)-1,1′-binaphthylC39H31P2S2[α]D = +3 (c 1, CH2Cl2)Source of chirality: enantiopure backbone and flash chromatography separation of diastereomersAbsolute configuration: (R,R)

(S,R)-2-(Methylphenylthiophosphinyl)-2′-(diphenylthiophosphinyl)-1,1′-binaphthylC39H31P2S2[α]D = −86 (c 0.25, CH2Cl2)Source of chirality: enantiopure backbone and flash chromatography separation of diastereomersAbsolute configuration: (S,R)

(R)-2-(Bisanisylthiophosphinyl)-2′-(diphenylthiophosphinyl)-1,1′-binaphthylC46H37O2P2S2[α]D = −61 (c 1, CH2Cl2)Source of chirality: enantiopure backboneAbsolute configuration: (R)

(R)-2-(Bis-o-tolylthiophosphinyl)-2′-(diphenylthiophosphinyl)-1,1′-binaphthylC46H37P2S2[α]D = +26.5 (c 1, CH2Cl2)Source of chirality: enantiopure backboneAbsolute configuration: (R)