Symmetric and asymmetric hydrindacene diones can be prepared by cyclization of a 3,3'-phenylenedipropanoic acid precursor. Conversion of ortho-, meta-, or para-phthaldialdehyde into the corresponding dicinnamic acid using a Knoevenagel or Perkin condensation, followed by hydrogenation over Pd catalyst affords the desired saturated acids. It was previously reported that treatment of the diacid with para-substitution in neat AlCl3/NaCl gives a 65-70% yield of as�hydrindacene-1,8-dione along with a small amount of s�hydrindacene-1,5-dione. The goal of this project was to try to explain the preference for the less thermodynamically stable asymmetric isomer. This was accomplished by repeating the reaction using different Lewis acids (e.g., BCl3, TiCl4, FeCl3, CuCl2, NiCl2, ZnCl2, SnCl4) to see how this affected the isomer distribution and overall yield. The corresponding ortho and meta diacids were similarly cyclized using a variety of Lewis acids to give as�hydrindacene-3,6-dione, or as�hydrindacene-1,6-dione and s�hydrindacene-1,7-dione, respectively. Full spectroscopic characterization and the product distribution for these reactions will be described and a possible explanation for the preference for certain isomers will be offered.

Factors affecting the cyclization of dicarboxylic acids to form hydrindacene diones

247th National Meeting (2014)

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