Chiral Diol-Based Organocatalysts in Enantioselective Reactions

Abstract

Organocatalysis has emerged as a powerful synthetic tool in organic chemistry in the last few decades. Among various classes of organocatalysis, chiral diol-based scaffolds, such as BINOLs, VANOLs, and tartaric acid derivatives, have been widely used to induce enantioselectivity due to the ability of the hydroxyls to coordinate with the Lewis acidic sites of reagents or substrates and create a chiral environment for the transformation. In this review, we will discuss the applications of these diol-based catalysts in different types of reactions, including the scopes of reactions and the modes of catalyst activation. In general, the axially chiral aryl diol BINOL and VANOL derivatives serve as the most competent catalyst for most examples, but examples of exclusive success using other scaffolds, herein, suggests that they should not be overlooked. Lastly, the examples, to date, are mainly from tartrate and biaryl diol catalysts, suggesting that innovation may be available from new diol scaffolds.

Asymmetric Organocatalytic C‐C Bond Forming Reactions with Organoboron Compounds: A Mechanistic Survey

“…Recent reviews address this topic in great detail from the synthetic point of view or either focus on a particular type of reaction or catalyst . Mainly, the asymmetric organocatalytic reactions developed so far have been 1,4‐additions to enones 1 to afford β‐substituted ketones 2 (Equation 1, Scheme ) and 1,2‐additions to aldehydes or ketones 3 or imines 4 to generate the alcohol or amine products 5 or 6 , respectively (Equation 2, Scheme ).…”

Accessing New 5‐α‐(3,3‐Disubstituted Oxindole)‐Benzylamine Derivatives from Isatin: Stereoselective Organocatalytic Three Component Petasis Reaction

“…[19a] We started our screening tests using mild reaction conditions (CH 2 Cl 2 as solvent, room temperature, absence of catalyst) and we noticed no formation of the desired product (4aaa) (Table , entry 1). A variety of organocatalysts were then investigated (see Supporting Information for further details); among them, ( R )‐BINOL[10a], [10c], was used under the same reaction conditions and the product (4aaa) was obtained with a yield of 60 % and an excellent enantioselectivity (95 % ee, Table , entry 2). L ‐Proline and ( R )‐(–)‐1,1'‐binaphthyl‐2,2'‐diyl hydrogenphosphate (( R )‐BNPPA) were also tested but unfortunately led to significant decreases in both yield and enantioselectivity (Table , entries 3 and 4).…”

Hydrogen Bonding and Internal or External Lewis or Brønsted Acid Assisted (Thio)urea Catalysts

“…One structure that merits special attention in this field is the TADDOL catalyst, one of the first chiral diol organocatalysts and one of the oldest chiral auxiliary in metal catalysis . The two hydroxyl groups of the molecule can act as a double hydrogen‐bond donor, through formation of bidentate complexes.…”