Multistereocenter-Containing Cyclopentanoids from Ynamides via Oxazolidinone-Controlled Nazarov Cyclization

作者：Manchala Narasimhulu; Law Hanson Y L; Kerr Daniel J; Volpe Rohan; Lepage Romain J; White Jonathan M; Krenske Elizabeth H; Flynn Bernard L^*

来源：Journal of Organic Chemistry, 2017, 82(13): 6511-6527.

DOI：10.1021/acs.joc.7b00082

Achieving ready-enantioselective access to multistereocenter-containing cyclopentyl rings is an area of great significance to organic synthesis. In this work, we describe a general protocol for accessing multistereocenter-containing cyclopentanoids from simple N-alkynyloxazolidinones (Ox-ynamides). This protocol involves conversion of Ox-ynamides into Ox-activated clivinyl, and aryl vinyl ketones that undergo facile Nazarov cyclization with excellent chemo,, regio-, and stereocontrol. The Ox auxiliary directs all aspects of reactivity and selectivity, both in the electrocyclization and in the subsequent transformations of the resulting oxyallyl intermediate. Stereoinduction in the electrocyclization results from a coupled-torque" mechanism in which rotation of the Ox group, driven by increasing orbital overlap of the nitrogen lone pair with the incipient oxyallyl cation, is coupled with the rotation of the termini of the pentadienyl cation, favoring a particular direction of conrotatory ring closure (torquoselectivity). The associated lone-pair stabilization of the transition state by Ox promotes cyclization of traditionally resistant substrates, broadening the scope of this asymmetric Nazarov-cyclization. The Ox group also facilitates the stereo- and regioselective incorporation of nucleophiles (Nu) and dienes, giving more complex, multistereocenter containing cyclopentanoids. Finally, the Ox group is readily removed and recovered or can be converted into other amine functionalities.

• 出版日期2017-7-7