Large-Scale Synthesis of Helicene-Like Molecules for the Design of Enantiopure Thin Films with Strong Chiroptical Activity

Helicenes are fascinating molecules owing to their unusual properties and applications in many fields from catalysis to organic electronics. Herein, we report a straightforward pathway for the synthesis of helicene-like molecules on a gram scale in an enantiopure form. We present a new and very efficient pathway able to yield the targeted helical dibenzo[c]acridine molecule 8 on the gram scale and in enantiomerically pure form. The first step is an Ullmann's homocoupling of tetralone 1, followed by the enlargement of the chromophore unit by a Friedlaender reaction to yield 4 or 6 (Figure).

The procedure is based on the key intermediate bis-tetralone,[2] which crystallizes as a conglomerate. Indeed, among the various methods for access to enantiopure compounds, preferential crystallization of conglomerates is probably the most attractive method that fits with large-scale production and high level of enantiomeric purity.

Bensalah-Ledoux, A., Pitrat, D., Reynaldo, T., Srebro-Hooper, M., Moore, B., Autschbach, J., Crassous, J., Guy, S. and Guy, L. (2016), Large-Scale Synthesis of Helicene-Like Molecules for the Design of Enantiopure Thin Films with Strong Chiroptical Activity. Chem. Eur. J.. doi:10.1002/chem.201504174   (Full paper)

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