Modular synthesis of the ClickFerrophos ligand family and their use in rhodium- and ruthenium-catalyzed asymmetric hydrogenation

A series of diphosphine ClickFerrophos ligands (CF), based on a triazoleferrocene backbone, was synthesized in a four-step sequence via click chemistry methodology. In addition to the four previously synthesized ligands CF1, CF4, CF7 and CF10, six novel CF ligands CF2–3 and CF5–8 were prepared. Hydrogenation reactions of alkenes and ketones were significantly improved upon by using CF ligands as rhodium- or ruthenium-complexes in which the % ee values can be optimized by choosing the appropriate CF ligand depending on the substrate.

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(1Rp)-(Diphenylphosphino)-2-[(1S)-(1-[5-(diphenylphosphino)-4-phenyl-1H-1,2,3-triazol-1-yl]ethyl)ferroceneC44H37FeN3P2Ee = 100%[α]D25=+183 (c 0.31, CHCl3)Absolute configuration: (S,Rp)

(1Rp)-(Diphenylphosphino)-2-[(1S)-(1-[5-(diphenylphosphino)-4-(2-methylphenyl)-1H-1,2,3-triazol-1-yl]ethyl)ferroceneC45H39FeN3P2Ee = 100%[α]D25=+220 (c 0.32, CHCl3)Absolute configuration: (S,Rp)

(1Rp)-(Diphenylphosphino)-2-[(1S)-(1-[5-(diphenylphosphino)-4-(2-fluorophenyl)-1H-1,2,3-triazol-1-yl]ethyl)ferroceneC44H36FeFN3P2Ee = 100%[α]D25=+175 (c 0.33, CHCl3)Absolute configuration: (S,Rp)

(1Rp)-(Diphenylphosphino)-2-[(1S)-(1-[5-(diphenylphosphino)-1H-1,2,3-triazol-1-yl]ethyl)ferroceneC44H36FeFN3P2Ee = 100%[α]D25=+95 (c 0.34, CHCl3)Absolute configuration: (S,Rp)

(1Rp)-(Di-3,5-xylylphosphino)-2-[(1S)-(1-[5-(di-3,5-xylylphosphino)-4-phenyl-1H-1,2,3-triazol-1-yl]ethyl)ferroceneC52H53FeN3P2Ee = 100%[α]D25=+161 (c 0.36, CHCl3)Absolute configuration: (S,Rp)

(1Rp)-(Di-3,5-xylylphosphino)-2-[(1S)-(1-[5-(di-3,5-xylylphosphino)-4-(2-fluorophenyl)-1H-1,2,3-triazol-1-yl]ethyl)ferroceneC52H52FeFN3P2Ee = 100%[α]D25=+160 (c 0.31, CHCl3)Absolute configuration: (S,Rp)

(1Rp)-(Dicyclohexylphosphino)-2-[(1S)-(1-[5-(dicyclohexylphosphino)-4-phenyl-1H-1,2,3-triazol-1-yl]ethyl)ferroceneC44H61FeN3P2Ee = 100%[α]D25=+97 (c 0.31, CHCl3)Absolute configuration: (S,Rp)

(1Rp)-(Diphenylphosphino)-2-[(1S)-(1-[5-(di-3,5-xylylphosphino)-4-phenyl-1H-1,2,3-triazol-1-yl]ethyl)ferroceneC48H45FeN3P2Ee = 100%[α]D25=+160 (c 0.26, CHCl3)Absolute configuration: (S,Rp)

(1Rp)-(Diphenylphosphino)-2-[(1S)-(1-[5-(di-(3,5-ditrifluoromethylphenyl)phosphino)-4-phenyl-1H-1,2,3-triazol-1-yl]ethyl)ferroceneC48H33FeF12N3P2Ee = 100%[α]D25=+140 (c 0.31, CHCl3)Absolute configuration: (S,Rp)

(1Rp)-(Diphenylphosphino)-2-[(1S)-(1-[5-(dicyclohexylphosphino)-4-phenyl-1H-1,2,3-triazol-1-yl]ethyl)ferroceneC44H49FeN3P2Ee = 100%[α]D25=+150 (c 0.23, CHCl3)Absolute configuration: (S,Rp)