title: Short Access to Belt Compounds with Spatially Close C=C Bonds and Their Transannular Reactions.
abstract: Two domino Diels-Alder adducts were obtained from 3,7-bis(cyclopenta-2,4-dien-1-ylidene)-cis-bicyclo[3.3.0]octane and dimethyl acetylenedicarboxylate or N-methylmaleimide under microwave irradiation. From the first adduct, a C20H24 diene with C2v symmetry was obtained by Zn/AcOH reduction, hydrolysis, oxidative decarboxylation, and selective hydrogenation. Photochemical [2+2] cycloaddition of this diene gave a thermally unstable cyclobutane derivative, which reverts to the diene. However, both the diene and the cyclobutane derivatives could be identified by X-ray diffraction analysis upon irradiation of the diene crystal. New six-membered rings are formed upon the transannular addition of bromine or iodine to the diene. The N-type selectivity of the addition was examined by theoretical calculations, which revealed the distinct susceptibility of the doubly bonded carbon atoms to the bromine attack.
authors.affiliation: Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia and Institut de Biomedicina (IBUB), Universitat de Barcelona, Av. Joan XXIII 27-31, 08028 Barcelona (Spain). camps@ub.edu.
authors.forename: Pelayo
authors.initials: P
authors.lastname: Camps
authors.affiliation: Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia and Institut de Biomedicina (IBUB), Universitat de Barcelona, Av. Joan XXIII 27-31, 08028 Barcelona (Spain).
authors.forename: Tània
authors.initials: T
authors.lastname: Gómez
authors.affiliation: Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia and Institut de Biomedicina (IBUB), Universitat de Barcelona, Av. Joan XXIII 27-31, 08028 Barcelona (Spain).
authors.forename: Ane
authors.initials: A
authors.lastname: Otermin
authors.affiliation: Departament de Cristallografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona, Martí Franquès s/n. 08028 Barcelona (Spain) and Unitat de Difracció de RX, Centres Científics i Tecnològics de la Universitat de Barcelona (CCiTUB), Solé i Sabarís 1-3, 08028 Barcelona (Spain).
authors.forename: Mercè
authors.initials: M
authors.lastname: Font-Bardia
authors.affiliation: Departament de Fisicoquímica, Facultat de Farmàcia and Institut de Biomedicina (IBUB), Universitat de Barcelona, Prat de la Riba 171, 08921 Santa Coloma de Gramenet (Spain).
authors.forename: Carolina
authors.initials: C
authors.lastname: Estarellas
authors.affiliation: Departament de Fisicoquímica, Facultat de Farmàcia and Institut de Biomedicina (IBUB), Universitat de Barcelona, Prat de la Riba 171, 08921 Santa Coloma de Gramenet (Spain).
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: Luque
keywords: X-ray diffraction; density functional calculations; domino reactions; photochemistry; polycycles