William Malachowski, Tapas Paul, and Sophia Phounsavath. Bryn Mawr College, Bryn Mawr, PA
The enantioselective synthesis of carbocyclic quaternary stereogenic centers remains an important challenge in organic chemistry and natural product synthesis. We have developed a method for the construction of quaternary stereocenters on a 2-cyclohexen-1-one ring with good to excellent levels of enantioselectivity. The quaternary stereocenter is created through a new synthetic sequence involving three reactions: the enantioselective Birch reduction-allylation, enol ether hydrolysis, and the Cope rearrangement. To illustrate the ability of the sequence to enantioselectively generate complex structures, a variety of substrates were demonstrated. Notably, the sequence works for the enantioselective generation of vicinal quaternary-tertiary stereocenters, the generation of congested arylic quaternary stereocenters, and hydroxyalkyl substituted quaternary stereocenters. The utility of this new tool in addressing challenges in natural product synthesis is illustrated in the first total synthesis of (-)-lycoramine.
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pubs3.acs.org/acs/journals/doilookup?in_doi=10.1021/jo0621423
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