Recent Advances in Organocatalytic Enantioselective Synthesis of Axially Chiral Allenes

Abstract

Axially chiral allenes occur on a wide range of natural products and synthetic molecules with significant biological activity. Furthermore, they are versatile building blocks in organic synthesis because of their inherent chemical properties. Accordingly, catalytic enantioselective synthesis of axially chiral allenes has been paid much attention. Benefited from the development of asymmetric organocatalysis, many simple and efficient methods in terms of different catalytic systems as well as reaction partners have been developed. This review will focus on the recent progress in the field of organocatalytic enantioselective synthesis of allenes , which is organized according to types of allenes and the catalyst system used.

Asymmetric Organocatalytic Reactions of Activated Racemic Allenes

“…Allenes were synthesized by employing the fundamental addition, substitution, elimination, and rearrangement reactions [25–30] . The electron‐deficient allenes having an axial chirality is a special sub‐class among them.…”

“…Allenes were synthesized by employing the fundamental addition, substitution, elimination, and rearrangement reactions. [25][26][27][28][29][30] The electron-deficient allenes having an axial chirality is a special sub-class among them. Typically, these can be accessed through Wittig reaction of ketenes with stabilized phosphorous ylides.…”

Asymmetric organocatalytic (3 + 2) annulation of propargylic alcohols with indolylnaphthalenols: synergistic construction of axial and central chirality

“…Recently, the catalytic enantioselective construction of axially chiral allenes has been well established. 10 In particular, the CPA-catalyzed reactions of functionalized propargylic alcohols provided robust access to axially chiral allenes via asymmetric conjugate addition of in situ formed propargylic p -quinone methides ( p -QMs), 11 propargylic aza- p -quinone methides (aza- p -QMs), 12 and propargylic methyleneindoles. 13 Independently, Shi and coworkers realized the asymmetric synthesis of aryl-pyrroloindoles with axial and central chirality via an organocatalytic asymmetric (2 + 3) cyclization of 3-arylindoles with propargylic alcohols (Scheme 1A).…”

Recent advances in the metal-catalyzed asymmetric synthesis of chiral allenes

“…Recently, a variety of strategies have been developed which have been documented by some excellent reviews. 5 For instance, diverse chiral allenes could be accessible under organocatalysis. Significant process in terms of asymmetric synthesis of chiral allenes via metal catalysis has been made in recent years as well.…”