Enantioselective synthesis of chiral 1,2-diamines by the catalytic ring opening of azabenzonorbornadienes: application in the preparation of new chiral ligands

In the presence of a rhodium catalyst (5 mol %) generated in situ from [Rh(cod)Cl]2 and (S,S′)-(R,R′)-C2-ferriphos-tolyl, the asymmetric ring-opening reaction of N-Boc-azabenzonorbornadienes with dibenzylamine proceeded with excellent enantioselectivity (up to >99% ee) to give the corresponding 1,2-diamine scaffolds in high yields. The sequential deprotection of the ring-opened products and treatment with tartaric acid gave the enantiomerically pure 1,2-diamine tartrate salts. These salts were used for the preparation of new chiral ligands such as the salen-type ligands and Trost-type ligands.

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(S,S)-N,N′-Bis(3,5-di-tert-butylsalicylidene)-1,2-diamino-1,2,3,4-tetrahydro-tetramethylnaphthaleneC40H54N2O2Ee >99%[α]D25=+265.8 (c 1.00, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S,S

(S,S)-N,N′-Bis(3,5-di-tert-butylsalicylidene)-1,2-diamino-1,2,3,4-tetrahydro-5,8-dimethyl-tetramethylnaphthaleneC42H58N2O2Ee >99%[α]D25=+219.8 (c 1.00, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S,S

(S,S)-N,N′-Bis(3,5-di-tert-butylsalicylidene)-1,2-diamino-1,2,3,4-tetrahydro-5,6,7,8-tetramethyl-tetramethylnaphthaleneC44H62N2O2Ee >99%[α]D25=+185.0 (c 1.00, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S,S

(S,S)-N,N′-Bis(3,5-di-tert-butylsalicylidene)-1,2-diamino-1,2,3,4-tetrahydro-6,7-dimethyl-tetramethylnaphthaleneC42H58N2O2Ee >99%[α]D25=+220.2 (c 1.00, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S,S

(−)-1N,2N-Bis[2′-(diphenylphosphino)benzoyl]-(1S,2S)-diamino-1,2,3,4-tetrahydronaphthaleneC48H40N2O2P2Ee >99%[α]D25=-29.8 (c 1.00, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: 1S,2S

(+)-1N,2N-Bis[2′-(diphenylphosphino)benzoyl]-(1S,2S)-diamino-5,8-dimethyl-1,2,3,4-tetrahydronaphthaleneC50H44N2O2P2Ee >99%[α]D25=+94.0 (c 1.00, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: 1S,2S

(+)-1N,2N-Bis[2′-(diphenylphosphino)benzoyl]-(1S,2S)-diamino-1,2,3,4-tetrahydro-5,6,7,8-tetramethylnaphthaleneC52H48N2O2P2Ee >99%[α]D25=+58.4 (c 1.00, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: 1S,2S

(−)-1N,2N-Bis[2′-(diphenylphosphino)benzoyl]-(1S,2S)-diamino-6,7-dimethyl-1,2,3,4-tetrahydronaphthaleneC50H44N2O2P2Ee >99%[α]D25=-28.9 (c 1.00, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: 1S,2S