Regio-, Diastereo-, and Enantioselective Organocatalytic Addition of 4-Substituted Pyrazolones to Isatin-Derived Nitroalkenes

Abstract

Hydroquinine 2,5-diphenyl-4,6-pyrimidinediyl diether [(DHQ)2Pyr] catalyzed the regio-, diastereo-, and enantioselective addition of 4-substituted pyrazolones to isatin-derived nitroalkenes, providing a variety of chiral alkenylpyrazolone adducts containing a tetrasubstituted stereocenter bearing an oxindole moiety with excellent yields, regioselectivity, and diastereoselectivity, as well as a moderate enantioselectivity (up to 98 % yield, > 20:1 E/Z ratio dr and 78 % ee). The reaction harnesses a nitroalkene as an alkenylating agent through a Nucleophilic Vinylic Substitution (SNV) reaction.