Organobase catalysed one-pot exo-selective synthesis of meso-spiro[cyclohexanone-pyrandione] derivativesElectronic supplementary information (ESI) available: NMR spectroscopic data for all the reported compounds 4a-f; chiral-HPLC analysis of compounds 4c and 4e; single-crystal X-ray diffraction data (CIF files and checkCIF reports) and additional crystallographic details for compounds 4b, 4e and 4f. CCDC 1527913-1527915. For ESI and crystallographic data in CIF or other electronic format see DOI

• Main Authors: Talhi, Oualid, Abdeldjebar, Hasnia, Belmiloud, Yamina, Hassaine, Ridha, Taibi, Nadia, Válega, Mónica, Paz, Filipe A. A, Brahimi, Meziane, Bachari, Khaldoun, Silva, Artur M. S
• Format: Article
• Language: English
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c7nj02168b

An exo -selective one-pot synthesis of novel spiro[cyclohexanone-pyrandione] derivatives through two sequential organobase-catalysed 1,4-conjugate additions of pyran-2,4-dione precursors on diarylideneacetone derivatives is described. The resulting 7,11-diaryl-2-oxaspiro[5.5]undec-3-ene-1,5,9-triones were obtained as a 2 : 1 mixture of exo - and endo -diastereomers and adopt a meso -form due to the bilateral symmetry existing in the scaffold. Chiral-HPLC, NMR and single-crystal X-ray diffraction (including synchrotron data) have been used to elucidate the spiro[cyclohexanone-pyrandione] structure, showing therefore the exo / endo -diastereomers obtained in a meso -form, the cis -7,11-diaryl configuration (equatorial position) and different conformational changes in the cyclohexanone skeleton both in liquid and solid states. DFT studies proved the exo -stereoselectivity of the reaction by determining the exo / cis equatorial-equatorial configuration as the most thermodynamically stable form of our spiro[cyclohexanone-pyrandione] skeleton, while the structural substitution has no effect. A facile metal-free one-pot exo -stereoselective synthesis of through two sequential organobase-catalysed 1,4-conjugate additions of pyran-2,4-diones on diarylideneacetone synthons is disclosed.