Highly enantio-stereoselective Ni-catalyzed reductive cyclization to cyclopentanes with chiral quaternary centres of trisubstituted allylic siloxanes

Abstract

The construction of chiral quaternary carbon stereocenters is a significant challenge in asymmetric synthesis. Catalytic synthesis of these structures with trisubstituted allylic alcohols is highly important. However, most of the reported methodologies required noble transition-metals. Herein we reported the first highly asymmetric stereoselective synthesis of cyclopentanes bearing chiral quaternary carbon stereocenters of trisubstituted allylic siloxanes by reductive cyclization of all carbon 1,6-alkynones with the non-noble nickel catalysis of Ni(cod)2 with P-chiral monophosphine ligand (S)-BIDIME. Various multi-substituted functionalized cyclopentanes were obtained in high yields (up to 96%), excellent enantioselectivities (up to >99% ee) and perfect stereoselectivities (>99:1 ​E/Z). Thirty-two examples were successfully established for this method. Clarified mechanism studies were investigated first time by React-IR and DFT calculations to understand and explain the ligand-control of excellent enantio-stereoselectivity. Gram-scale reaction and control experiments were carried out. A new reaction design was proposed for further application of this type of catalysis.

Keywords

• All carbon 1,6-alkynone
• Ni-catalyzed reductive cyclization
• Stereoselective asymmetric catalysis
• Cyclopentane with chiral allylic quaternary stereocenter
• P-Chiral monophosphine ligand