title: Enantioselective Ring-Opening Polymerization of rac-Lactide Dictated by Densely Substituted Amino Acids.
abstract: Organocatalysis is becoming an important tool in polymer science because of its versatility and specificity. To date a limited number of organic catalysts have demonstrated the ability to promote stereocontrolled polymerizations. In this work we report one of the first examples of chirality transfer from a catalyst to a polymer in the organocatalyzed ring-opening polymerization (ROP) of rac-lactide (rac-LA). We have polymerized rac-LA using the diastereomeric densely substituted amino acids (2S,3R,4S,5S)-1-methyl-4-nitro-3,5-diphenylpyrrolidine-2-carboxylic acid (endo-6) and (2S,3S,4R,5S)-1-methyl-4-nitro-3,5-diphenylpyrrolidine-2-carboxylic acid (exo-6), combined with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a cocatalyst. Both diastereoisomers not only showed the ability to synthesize enriched isotactic polylactide with a Pmhigher than 0.90 at room temperature but also were able to preferentially promote the polymerization of one of the isomers (l or d) with respect to the other. Thus, exo-6 preferentially polymerized l-lactide, whereas endo-6 preferred d-lactide as the substrate. Density functional theory calculations were conducted to investigate the origins of this unique stereocontrol in the polymerization, providing mechanistic insight and explaining why the chirality of the catalyst is able to define the stereochemistry of the monomer insertion.
authors.affiliation: POLYMAT, University of the Basque Country UPV/EHU , Joxe Mari Korta Center, Avda. Tolosa 72, 20018 Donostia/San Sebastian, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Sanchez-Sanchez
authors.affiliation: Departamento de Química Orgánica I and Instituto de Innovación en Química Avanzada (ORFEO-CINQA), University of the Basque Country UPV/EHU , P° Manuel Lardizabal 3, 20018 Donostia/San Sebastian, Spain.
authors.forename: Ivan
authors.initials: I
authors.lastname: Rivilla
authors.affiliation: Departamento de Química Orgánica I and Instituto de Innovación en Química Avanzada (ORFEO-CINQA), University of the Basque Country UPV/EHU , P° Manuel Lardizabal 3, 20018 Donostia/San Sebastian, Spain.
authors.forename: Maddalen
authors.initials: M
authors.lastname: Agirre
authors.affiliation: POLYMAT, University of the Basque Country UPV/EHU , Joxe Mari Korta Center, Avda. Tolosa 72, 20018 Donostia/San Sebastian, Spain.
authors.forename: Andere
authors.initials: A
authors.lastname: Basterretxea
authors.affiliation: Department of Polymer Science and Technology, Institute of Polymer Materials, University of the Basque Country UPV/EHU , P° Manuel Lardizabal 3, 20018 Donostia/San Sebastian, Spain.
authors.forename: Agustin
authors.initials: A
authors.lastname: Etxeberria
authors.affiliation: POLYMAT, University of the Basque Country UPV/EHU , Joxe Mari Korta Center, Avda. Tolosa 72, 20018 Donostia/San Sebastian, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Veloso
authors.affiliation: POLYMAT, University of the Basque Country UPV/EHU , Joxe Mari Korta Center, Avda. Tolosa 72, 20018 Donostia/San Sebastian, Spain.|Ikerbasque, Basque Foundation for Science , E-48011 Bilbao, Spain.|Department of Polymer Science and Technology, Institute of Polymer Materials, University of the Basque Country UPV/EHU , P° Manuel Lardizabal 3, 20018 Donostia/San Sebastian, Spain.
authors.forename: Haritz
authors.identifier: 0000-0002-6268-0916
authors.initials: H
authors.lastname: Sardon
authors.affiliation: POLYMAT, University of the Basque Country UPV/EHU , Joxe Mari Korta Center, Avda. Tolosa 72, 20018 Donostia/San Sebastian, Spain.|Ikerbasque, Basque Foundation for Science , E-48011 Bilbao, Spain.
authors.forename: David
authors.identifier: 0000-0002-0788-7156
authors.initials: D
authors.lastname: Mecerreyes
authors.affiliation: Departamento de Química Orgánica I and Instituto de Innovación en Química Avanzada (ORFEO-CINQA), University of the Basque Country UPV/EHU , P° Manuel Lardizabal 3, 20018 Donostia/San Sebastian, Spain.|Donostia International Physics Center (DIPC) , P° Manuel Lardizabal 4, 20018 Donostia/San Sebastian, Spain.
authors.forename: Fernando P
authors.identifier: 0000-0002-4526-2122
authors.initials: FP
authors.lastname: Cossío
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D004146:Dioxanes / Q000737:chemistry*; D015394:Molecular Structure; D011091:Polyesters / Q000138:chemical synthesis* / Q000737:chemistry; D058105:Polymerization; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D004146:Dioxanes; D011091:Polyesters; C033616:poly(lactide); C091880:dilactide