Synthesis of New Bis-Arsine Chiral Ligands Based on Natural Carbohydrates

SOL C. PARAJÓN PUENZO; JOAQUÍN ARATA BADANOA; MARTIN G. LOPEZ VIDAL; OSCAR VARELA; SANDRA E. MARTÍN

Congreso; 15th Brazilian Meeting on Organic Synthesis (15th BMOS); 2013

SYNTHESIS OF NEW BIS-ARSINE CHIRAL LIGANDS BASED ON NATURAL CARBOHYDRATESSol C. Parajón Puenzoa,b; Joaquín Arata Badanoa; Martin G. Lopez Vidala; Oscar Varelab; Sandra E. MartínaaINFIQC, Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina -bDpto. Química Orgánica, CIHIDECAR-CONICET-UBA, Facultad de Ciencias Exactas y Naturales, Buenos Aires, Argentina*e-mail spuenzo@mail.fcq.unc.edu.arKeywords: Ligand, Cross-Coupling, INTRODUCTIONTransition-metal-catalyzed asymmetric allylic substitutions have become some of the most powerful tools for asymmetric C−C and C−heteroatom bond formation. ,1b Chiral diphosphine ligands have been one of the largest classes of ligands used in asymmetric substitutions. The most important chiral ligand designed specifically for this type of reaction is called Trost ligand (1) which has been employed with very good results. Based on this structure, a similar family of ligands (2) have been prepared by our research group where the significant change was that a phosphine atom was replaced for an arsine atom. Arsines have several examples where arsine complexes show more effective catalysis or more selectivity than phosphines in transition-metal-catalyzed reactions.2Figure 1. Phosphine and arsine Trost modular ligands.In the past 10 years significant attention has been turned towards the use of chiral ligands based on natural carbohydrates like the chiral scaffold (3).3 RESULTS AND DISCUSSIONAfter a Fischer sterification of carboxylic acid 4, the ester 5 obtained was allowed to react by a Stille reaction in order to incorporate to arsine group. Through hydrolysis of arsine ester 6 was obtained the carboxylic acid 7.Treatment of D-Glucosamine (8) with Acetic anhidride led to conversion into the N-acetyl glucosamine and the free anomeric hydroxyl group was protected with benzyl alcohol giving the product (9), as the last protective reaction was the treatment with benzaldehyde in order to protect the 4,6-O-benzylidene derivative and the desprotection of amine, it gave the carbohydrate (10). This key sugar intermediate was used as chiral scaffold.Condensation of the free hydroxyl group and the free amine of the carbohydrate with acid (7) afforded the ligand 11.   Figure 2. Synthesis of bis-arsine LigandCONCLUSIONThe sugar-based amino precursor 5 has been synthesized straightforward from D-Glucosamine. This building block was employed as key intermediate in the synthesis of new Bis-Arsine Ligand.ACKNOWLEDGEMENTSWe are indebted to ANPCyT, UBA, UNC and CONICET for their financial support.REFERENCES1. a) Trost, B. M.; Crawley, M. L. Chem. Rev. 2003, 103, 2921-2943. b) Trost, B. M. J. Org. Chem. 2004, 69, 5813-5837.2. Uberman, P. M.; Lanteri, M. N.; Parajon Puenzo, S. C.; Martín, S. E. Dalton Trans. 2011, 40, 9229−9237 b) Uberman, P. M.; Caira M. R.; Martín, S. E., Organometallics 2013, 32, 3220−3226.3. Reviews: a) M. Dieguez, C. Claver and O. Pa`mies, Eur. J. Org. Chem., 2007, 4621; b) M. Dieguez, O. Pamies and C. Claver, Chem.Rev., 2004, 104, 3189.