An unprecedented enantioselective peroxyhemiacetalization/oxa-Michael addition cascade of ortho-formyl homochalcones has been developed using cinchona-alkaloid-based chiral bifunctional organocatalysts to provide cis-configured exo-peroxyacetals, a new class of organic peroxide, in good yields with excellent enantio- and diastereoselectivities. The resulting cis-configured exo-peroxyacetals were converted into the corresponding trans-configured peroxyacetals without affecting the enantioselectivity. Furthermore, the displacement of the peroxide moiety of exo-peroxyacetals with various nucleophiles has been demonstrated to afford 1,3-disubstituted isochromans with high diastereoselectivities and excellent enantioselectivities.
Bibliographical noteFunding Information:
This work has been funded by CSIR, New Delhi and IISER Bhopal. S.M. and B.P. thank UGC and CSIR, respectively, New Delhi, India for the fellowship. We are thankful to Mr. L. M. Jha and Ms. A. Upadhyay for the crystal analysis. The support from Mr. Barnala Ravindra (IISER-B) is acknowledged.
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- Michael addition
- asymmetric synthesis