Enantioselective Synthesis of Cyclopentanes by Phosphine-Catalyzed ß,γ-Annulation of Allenoates.

ABSTRACT

Herein, we report the enantioselective phosphine-catalyzed ß,γ-annulation of electron-poor allenes with bifunctional malonates. The reaction exploits a 2C phosphonium synthon that when accessed using (R)-SITCP gives 23 cyclopentanes with high stereoselectivity (most >955 er and >91 dr) and yield. In addition to the (3+2) annulation, a one-pot three-component variant to give the same cyclopentanes and a (3+2) annulation/Dieckmann cyclization cascade, along with mechanistic studies, are reported.