Enantioselective iridium-catalyzed allylic substitution with a Reformatsky reagent: direct construction of β-stereogenic homoallylic esters.

Autor: Pal, Debasis, Veeranna, Kirana D., Wong, Yuk Fai, Evans, P. Andrew
Zdroj: SCIENCE CHINA Chemistry; Nov2024, Vol. 67 Issue 11, p3791-3797, 7p
Abstrakt: The Reformatsky reagent derived from ethyl bromoacetate circumvents the challenge associated with the direct regio- and enantioselective iridium-catalyzed allylic alkylation with an unstabilized aliphatic ester enolate. Notably, this work represents the first example of using a Reformatsky reagent in a metal-allyl reaction, which permits the direct construction of enantioenriched β-stereogenic homoallylic esters without preactivation of the pronucleophile or post-reaction modification of the product (e.g., thermal decarboxylation of a 1,3-dicarbonyl). Moreover, the process allows the coupling of a broad range of sterically and electronically diverse electrophiles bearing aryl, heteroaryl and alkenyl derivatives, including the significantly more challenging alkyl-substituted allylic carbonates. The versatility of the ester product is exemplified by a series of functional group manipulations and the development of a concise and efficient enantioselective total synthesis of the natural product, (+)-descurainolide A. Finally, mechanistic studies indicate that the zinc enolate behaves as a soft nucleophile that undergoes outer-sphere alkylation. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index