BINOL-Al catalysed asymmetric cyclization and amplification: preparation of optically active menthol analogs

Abstract

We report a highly selective asymmetric ring-closing ene reaction catalysed by aluminum complexes with chiral BINOL. This reaction yields optically active 6-membered cyclized alcohols from unsaturated aldehydes, with good diastereo- and enantioselectivities. Asymmetric amplification of this reaction was investigated by varying the ee of the BINOL employed in the catalyst.

BINOL-Al catalyzed kinetic resolution of citronellal analogues: synthesis of a variety of fragrances

“…These complexes have a metal center between two parallel aromatic rings. 14,28 During the transition state of the ringclosing ene reaction, the aromatic rings are in close proximity to 3-vinylcitronellal. This narrow space results in the good diastereoand enantioselectivity seen in the reaction.…”

Catalytic Asymmetric Amino Acid and Its Derivatives by Chiral Aldehyde Catalysis

“…Inspired by this well-established enamine activation mode, synthetic chemists adopted this concept in the laboratory. Several biomimetic chiral BINOL aldehyde analogs or chiral pyridoxal analogs have been developed and employed in Mannich reactions ( Dai et al, 2017 ), aldol reactions ( Li et al, 2008 ), cyclization reaction ( Itoh et al, 2015 ), and Cope-type hydroaminations of allylic amines ( Guimond et al, 2012 ). In 2018, Zhao and coworkers designed N-quaternized pyridoxals as ideal enzyme mimics and successfully applied them in asymmetric Mannich reactions of glycinate with aryl N-diphenylphosphinyl imines ( Chen et al, 2018 ).…”

Biomimetic Approaches to Synthesis of Cannabidiol

“…Thus, we explored methods to access 9a or 9c from available terpenes. and even demonstrated with citronellal 31 39 , ene reactions fail with α,β-unsaturated carbonyls 40 .…”