As a spinoff of our mechanistic studies of phenylchlorocarbene addition to dibenzocyclooctyne (1b) and its open-chain derivative 1a, we are investigating computationally and experimentally the rotational barriers of relevant α,β-unsaturated diarylketones 2a-h. Computationally, the barriers of rotation of 2a and 2b are 4.1-4.3 and 5.1-8.1 kcal/mol, respectively (M06-2X/6-31G(d)). The rotation of 2c and of 2d costs 7.6-8.5 and 9.1-9.8 kcal/mol, respectively (M06-2X/6-31G(d)). Experimentally, we are conducting steady-state room-temperature irradiation at 254 nm of 2b-d in CH2Cl2. We have observed significant change in the UV-Vis spectrum of a mixture of diastereomers 2c + 2d upon irradiation. We will also report our study of the photochemistry of 2b. We have also planned variable temperature NMR experiments to experimentally measure the rotational barriers of 2b-d with comparison to the calculated values.

Rotational barriers of substituted α,β-unsaturated diarylketones

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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