Synthesis of a water-soluble cationic chiral diamine ligand bearing a diguanidinium and application in asymmetric transfer hydrogenation

A novel water-soluble cationic N-monosulfonated chiral diamine ligand diguanidinium 1c was easily prepared from (R,R)-DPEN and its rhodium complex and was successfully applied in the asymmetric transfer hydrogenation of prochiral ketones and imines in water by using sodium formate and formic acid as co-hydrogen donors. Various substrates were reduced with high yields and good to excellent enantioselectivities (up to >99% ee).

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(1R,2R)-1,2-Bis(3-nitrophenyl)ethylenediamineC14H14N4O4Ee >99%[α]D25=+109.3 (c 1.0, CH3OH)Source of chirality: (1R,2R)-1,2-diphenylethylenediamineAbsolute configuration: (1R,2R)

(1R,2R)-N-(p-Toluenesulfonyl)-1,2-bis(3-nitrophenyl)ethylenediamineC21H20N4O6SEe >99%[α]D28=+32.9 (c 0.98, CH3OH)Source of chirality: (1R,2R)-1,2-bis(3-nitrophenyl)ethylenediamineAbsolute configuration: (1R,2R)

(1R,2R)-N-(p-Toluenesulfonyl)-N′-tert-butyloxycarbonyl-1,2-bis(3-nitrophenyl)-ethylenediamineC26H28N4O8SEe >99%[α]D20=+22.4 (c 0.51, CH3OH)Source of chirality: N-((1R,2R)-2-amino-1,2-bis(3-nitrophenyl)-ethyl)-4-methylbenzenesulfonamideAbsolute configuration: (1R,2R)

(1R,2R)-N-(p-Toluenesulfonyl)-N′-tert-butyloxycarbonyl-1,2-bis(3-aminophenyl)ethylenediamineC26H32N4O4SEe >99%[α]D20=+47.1 (c 0.54, CH3OH)Source of chirality: tert-butyl-(1R,2R)-2-(4-methylphenylsulfonamido)-1,2-bis(3-nitrophenyl)ethylcarbamateAbsolute configuration: (1R,2R)

(1R,2R)-N-(p-Toluenesulfonyl)-N′-tert-butyloxycarbonyl-1,2-bis(3-N,N′-di-tert-butyloxycarbonylguanidinophenyl)ethylenediamineC48H68N8O12SEe >99%[α]D20=+41.7 (c 0.7, CH3OH)Source of chirality: tert-butyl-(1R,2R)-1,2-bis(3-aminophenyl)-2-(4-methylphenylsulfonamido)ethylcarbamateAbsolute configuration: (1R,2R)

(1R,2R)-N-(p-Toluenesulfonyl)-1,2-bis(3-guanidinophenyl)-1,2-ethylenediamine trifluoroacetic acid saltC29H31F9N8O8SEe >99%[α]D20=+19.8 (c 0.64, CH3OH)Source of chirality: N-(p-toluenesulfonyl)-N-tert-butyloxycarbonyl-1,2-bis(3-N,N′-di-tert-butyloxycarbonylguanidinophenyl)ethylenediamineAbsolute configuration: (1R,2R)