Temperature Dual Enantioselective Control in a Rhodium-Catalyzed Michael-Type Friedel-Crafts Reaction: A Mechanistic Explanation

Méndez, Isabel ; Rodríguez-Martínez, Ricardo (Universidad de Zaragoza) ; Polo, Víctor (Universidad de Zaragoza) ; Passarelli, Vicenzo ; Lahoz, Fernando J. (Universidad de Zaragoza) ; García-Orduña, Pilar (Universidad de Zaragoza) ; Carmona, Daniel

Resumen: By changing the temperature from 283 to 233 K, the S (99% ee)orR (96 % ee)enantiomer of the Friedel–Crafts (FC) adduct of the reaction between N-methyl-2-methylindole and trans-b-nitrostyrene can be obtained by using (S Rh ,R C )-[(h 5 -C 5 Me 5 )Rh{(R)-Prophos}(H 2 O)][SbF 6 ] 2 as the catalyst precursor.This catalytic systempresents two otheruncom - mon features:1)The ee changes with reactio ntime showing trends that depend on the reactiontemperature and 2) an increase in the catalyst loading results in adecrease in the ee of the S enantiom er.Detection and characteriza tion of the intermediate metal-nitroalkene and metal–aci-nitro complexes, the free aci-nitro compound, and the FC adduct-complex, together with solution NMR measuremen ts, theo- retical calculations, and kinetic stu dies have allowed us to propose two plausible alternative catalytic cycles. On the basis of these cycles,all the above -mentioned observations can be rationalized. In particular,the reversibility of one of the cycles toget her with the kinetic resolution of the intermediate aci-nitro complexes accountfor the high ee values achieved in both antipodes.Onthe other hand, the results of kinetic measurements explain the unusual effect of the increment in catalyst loading.

Idioma: Inglés

DOI: 10.1002/chem.201601301

Año: 2016

Publicado en: Chemistry - A European Journal 22, 31 (2016), 11064-11083
ISSN: 0947-6539

Factor impacto JCR: 5.317 (2016)

Categ. JCR: CHEMISTRY, MULTIDISCIPLINARY rank: 29 / 166 = 0.175 (2016) - Q1 - T1

Factor impacto SCIMAGO: 2.351 - Chemistry (miscellaneous) (Q1)

Financiación: info:eu-repo/grantAgreement/ES/MINECO/Consolider-Ingenio/CSD2006-0015
Financiación: info:eu-repo/grantAgreement/ES/MINECO/CTQ2012-32095
Financiación: info:eu-repo/grantAgreement/ES/MINECO/CTQ2015-66079-P

Tipo y forma: Article (PostPrint)

Área (Departamento): Área Química Inorgánica (Dpto. Química Inorgánica)
Área (Departamento): Área Química Física (Dpto. Química Física)