Unprecedented Diastereoselective Arylogous Michael Addition of Unactivated Phthalides

Abstract
The first highly enantioselective arylogous Michael reaction (AMR) of 3-unsubstituted phthalides has been described. This phase-transfer methodology, which uses catalytic amounts of KOH/18-crown-6 catalyst in mesitylene in the presence of N,O-bis(trimethylsilyl)acetamide (BSA), gives access to a broad range of 3-monosubstituted phthalides with high levels of syn diastereoselectivity and good yields, starting from 3-unsubstituted derivatives and diverse α,β-unsaturated carbonyl compounds. The reaction also applies to unactivated 3-alkyl phthalides to afford 3,3-dialkyl derivatives. A plausible mechanism has been suggested. DFT analysis of possible transition states gives a rationale of the high syn diastereoselectivity observed and its correlation with the solvent's dielectric constant.

Citation
Sicignano, M., Schettini, R., Sica, L., Pierri, G., De Riccardis, F., Izzo, I., … Della Sala, G. (2019). Unprecedented Diastereoselective Arylogous Michael Addition of Unactivated Phthalides. Chemistry – A European Journal, 25(29), 7131–7141. doi:10.1002/chem.201900168

Acknowledgements
Financial support was provided from the University of Salerno (FARB). The computing resources used within this project have been provided by CRESCO/ENEAGRID High Performance Computing infrastructure and its staff. We thank Dr Patrizia Iannece for HR-ESI-MS

Publisher
Wiley

Journal
Chemistry – A European Journal

DOI
10.1002/chem.201900168

Additional Links
https://onlinelibrary.wiley.com/doi/abs/10.1002/chem.201900168

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