Abstract
The bond length between C8-C9 in (1′ R,4′ S,4a′ R,8a′ S)-6′,7′-dimethyl-1′,4′,4a′,8a′-tetrahydrospiro [cyclopropane-1,9′-[1,4]methanonaphthalene]-5′,8′-dione is 1.571 (2) Å and between C7-C12 is 1.567 (2) Å which are longer than the corresponding bond length for saturated bicyclic systems (1.531-1.535 Å). This paper reports the correlation between bond length and the ease of retro Diels −Alder reaction.
We examined the crystal structure of (1′R,4′S,4a′R,8a′S)-6′,7′-dimethyl-1′,4′,4a′,8a′-tetrahydrospiro[cyclopropane-1,9′-[1,4] methano- naphthalene]-5′,8′-dione and found that the bond length between atoms connecting diene and the dienophile is somewhat longer than the normal C–C bond length. The increased bond length is responsible for the facile rDA reaction of 5.
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Acknowledgements
We would like to acknowledge the DST, New Delhi for the financial support. We also thank, SAIF-Mumbai for recording the spectral data. S K thanks DST, New Delhi for the award of a J C Bose fellowship. S K thanks Darshan Mhatre for his help regarding X-ray data collection.
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X-ray diffraction data were collected on an OXFORD XCALIBUR-S CCD single-crystal X-ray diffractometer. The structure was solved and refined by full-matrix least-squares techniques on F2 using the SHELX-97 program (Sheldrick, 1997). Crystallographic data (excluding structure factors) for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication Compound 5CCDC 958630. Copies of available material can be obtained, free of charge, on application to the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (e-mail: deposit@ccdc.cam.ac.uk).
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KOTHA, S., BANERJEE, S. & SHAIKH, M. Correlation between carbon–carbon bond length and the ease of retro Diels–Alder reaction. J Chem Sci 126, 1369–1371 (2014). https://doi.org/10.1007/s12039-014-0709-6
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DOI: https://doi.org/10.1007/s12039-014-0709-6