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Review of 'Bromosubstituted Norbornadienes and Their Reversible Photolytic Transformation to Quadricyclanes'

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5
Synthetic plan is comprehensibly outlined and the results are well documented.
Average rating:
    Rated 4.5 of 5.
Level of importance:
    Rated 4 of 5.
Level of validity:
    Rated 5 of 5.
Level of completeness:
    Rated 4 of 5.
Level of comprehensibility:
    Rated 5 of 5.
Competing interests:
None

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Bromosubstituted Norbornadienes and Their Reversible Photolytic Transformation to Quadricyclanes

 Thomas Sørensen (corresponding) ,  Anders Østergaard Madsen,  Peter (2014)
Two new model systems for use within the rapidly developing ultrafast time resolved x-ray scattering techniques have been prepared. Their photoisomerisation from norbornadiene to quadricyclane was found to be a suitable reaction to follow. Simulations of scattering patterns (not included in this report) showed that if heavy atoms are included in these molecular structures, then the transformation can be followed by transient x-ray scattering techniques. Two new bromosubstituted norbornadienes were synthesised and characterised. Absorption spectroscopy showed that the norbornadienes are converted quantitatively to quadricyclanes under UV irradiation. NMR studies showed that the process was fully reversible and that the norbornadienes could be completely recovered even without addition of catalysts. Furthermore, it was shown that the formation of quadricyclane from norbornadiene was unaffected by triplet sensitizers. The two new model systems synthesised thus are strong candidates for use in time resolved x-ray scattering studies both in gas and condensed phases.
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    Review information

    10.14293/S2199-1006.1.SOR-CHEM.AKS7SX.v1.RHQFND

    This work has been published open access under Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com.

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    Review text

    In this paper, two new norbornadienes with bromine substituents have been synthesized and characterized. The researchers have investigated photoisomerisation of two new norbornadienes to quadricyclanes. The synthetic plan is comprehensibly outlined and the results are well documented. However, as the article stands, the NMR data needs correction. These points are enumerated below.

    1. In the 1H-NMR data of compound 4, “q” term must be two “doublet”. As methylenic carbon is adjacent to chiral carbon, it is clear that diastereomeric methylene hydrogen atom resonate at different regions as expected and must be two doublet (typically AB system). So, two different shift data and “d“ term must be used instead of “q” term.

    2. Please check also 1H-NMR data of compound 6. The signal at 2.16 ppm is requiring to revision. The diastereomeric methylene hydrogen cannot be given as only one “doublet”. 13-NMR data of compound 6 is also need correction. The signal at 77.58, 77.26, and 76.94 ppm cannot be belong to structure and it must be signal of solvent (CDCl3).

    3. Please check also 13C-NMR data of compound 8. I think that signal of carbonyl group is missing. Please check also a missing data at olefinic region and excess signal at (6.42 ppm ?) aliphatic region.

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