126310 20241125101153.0 doi 10.1039/d3ob00284e sideral 133629 ART-2023-133629 eng Sierra, Sonia Synthesis of 1,2-diaminotruxinic d-cyclobutanes by BF₃-controlled [2 + 2]-photocycloaddition of 5(4<i>H</i>)-oxazolones and stereoselective expansion of d-cyclobutanes to give highly substituted pyrrolidine-2,5-dicarboxylates 2023 Access copy available to the general public Unrestricted The irradiation of (Z)-4-arylidene-5(4H)-oxazolones 1a–1u with blue light (465 nm) in the presence of the photosensitizer [Ru(bpy)3](BF4)2 (2.5 mol%) and the Lewis acid BF3·OEt2 (2 equiv.) in deoxygenated methanol at room temperature affords the corresponding 1,2-diaminotruxinic cyclobutane bis-amino esters 2a–2u stereoselectively as the δ-isomer. Characterization of cyclobutanes 2 shows that the photocycloaddition takes place by the coupling of two Z-oxazolones in a head-to-head 1,2-anti way. This change in the orientation of the coupling is promoted by O- or/and N-bonding of the BF3 additive. The δ-cyclobutanes 2 undergo a ring expansion when heated in methanol in the presence of NaOMe (1/1 molar ratio) to give densely substituted pyrrolidine-2,5-dicarboxylates 3 in a regio- and stereoselective way. The mechanism of the cyclobutane-to-pyrrolidine ring expansion has been elucidated using DFT methods. info:eu-repo/grantAgreement/ES/DGA/E11-20R info:eu-repo/grantAgreement/ES/DGA/E19-20R info:eu-repo/grantAgreement/ES/MCINN-FEDER/PGC2018-093451-B-I00 info:eu-repo/grantAgreement/ES/MICINN AEI PID2019-110008GB-I00 info:eu-repo/grantAgreement/ES/MICINN/PID2019-106394GB-I00 info:eu-repo/semantics/openAccess by-nc http://creativecommons.org/licenses/by-nc/3.0/es/ 2.9 2023 CHEMISTRY, ORGANIC 13 / 58 = 0.224 2023 Q1 T1 0.607 2023 Organic Chemistry 2023 Q2 Physical and Theoretical Chemistry 2023 Q2 Biochemistry 2023 Q3 5.5 2023 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion López, Rosa Gómez-Bengoa, Enrique Falvello, Larry R. Universidad de Zaragoza (orcid)0000-0002-0444-996X Urriolabeitia, Esteban P. 2010 760 Universidad de Zaragoza Dpto. Química Inorgánica Área Química Inorgánica 21, 15 (2023), 3203-3213 Org. biomol. chem. Organic & Biomolecular Chemistry 1477-0520 1931034 http://zaguan.unizar.es/record/126310/files/texto_completo.pdf Versión publicada 2660827 http://zaguan.unizar.es/record/126310/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:126310 articulos driver 2024-11-22-12:07:44 ARTICLE