Abstract
AbstractAn N‐propargyl pyrroloimidazolone with syn stereochemistry derived from L‐proline serves as a starting material for the diastereoselective synthesis (>95:5 dr) of propargyl alkynes or allenamides by direct quench of its lithiated intermediate with alkylating agents or aldehydes/ketones, respectively. Use of the epimeric anti pyrroloimidazolone starting material results in reversal of stereochemistry at the propargyl position in the products, without the need to prepare a separate substrate from D‐proline. Lithiation of the syn pyrroloimidazolone and quench with prochiral benzaldehydes without prior transmetalation gives allenamides with crystallographically verified atypical stereochemistry of the benzylic alcohol in >95:5 dr. The epimeric series of benzylic alcohols may also be obtained in >95:5 dr by employing transmetalation with chlorotitanium triisopropoxide prior to aldehyde quench. Density Functional Theory (DFT) computational studies provide a rationale for the change in benzylic alcohol stereochemistry by virtue of differing stereofacial attack in 6,5‐bicyclic (Li) or 6‐membered (Ti) transition states.magnified image
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.