Recently, the use of enantiomerically pure counteranions for the induction of asymmetry in reactions proceeding through cationic intermediates has emerged as an exciting new concept, which has been ...termed asymmetric counteranion‐directed catalysis (ACDC). Despite its success, the concept has not been fully defined and systematically discussed to date. This Review closes this gap by providing a clear definition of ACDC and by examining both clear cases as well as more ambiguous examples to illustrate the differences and overlaps with other catalysis concepts.
Opposites attract: This simple realization is the basis for asymmetric counteranion‐directed catalysis (ACDC). All reactions proceeding via cationic intermediates are accompanied by a counteranion. Inducing high enantioselectivities in these reactions merely by ion pairing with an enantiomerically pure counteranion has been achieved for the first time during recent years.
Herein, we describe the first catalytic asymmetric intramolecular 4+2 cycloaddition of in situ generated ortho‐quinone methides. In the presence of a confined chiral imidodiphosphoric acid catalyst, ...various salicylaldehydes react with dienyl alcohols to give transient ortho‐quinone methide intermediates, which undergo an intramolecular 4+2 cycloaddition to provide highly functionalized furanochromanes and pyranochromanes in excellent diastereoselectivity and enantioselectivity.
Chromane synthesis: An organocatalytic asymmetric intramolecular 4+2 cycloaddition of in situ generated ortho‐quinone methides is described. In the presence of a chiral imidophosphoric acid catalyst, various salicylaldehydes react with dienyl alcohols to afford highly functionalized furanochromanes or pyranochromanes in excellent diastereo‐ and enantoselectivity.
IDPi Catalysis Schreyer, Lucas; Properzi, Roberta; List, Benjamin
Angewandte Chemie International Edition,
September 9, 2019, Letnik:
58, Številka:
37
Journal Article
Recenzirano
Odprti dostop
High acidity and structural confinement are pivotal elements in asymmetric acid catalysis. The recently introduced imidodiphosphorimidate (IDPi) Brønsted acids have met with remarkable success in ...combining those features, acting as powerful Brønsted acid catalysts and “silylium” Lewis acid precatalysts in numerous thus far inaccessible transformations. Substrates as challenging to activate as simple olefins were readily transformed, ketones were employed as acceptors in aldolizations allowing sub‐ppm level catalysis, whereas enolates of the smallest donor aldehyde, acetaldehyde, did not polymerize but selectively added a single time to a variety of acceptor aldehydes.
The development and application of imidodiphosphorimidates (IDPis) as powerful Brønsted acid catalysts and “silylium” Lewis acid precatalysts are discussed in this Minireview. Due to their extraordinarily high acidity and confined chiral microenvironment, IDPis outperformed all previously reported chiral Brønsted acids in a number of challenging C−C and C−O bond‐forming transformations.
A method of reductive amination without an external hydrogen source is reported. Carbon monoxide is used as the reductant. The reaction proceeds efficiently for a variety of carbonyl compounds and ...amines at low catalyst loadings and is mechanistically interesting as it does not seem to involve molecular hydrogen.
Look, no H2! Reductive amination without an external hydrogen source has been developed using carbon monoxide as the reductant and rhodium acetate (0.2–1 mol %) as catalyst. The method tolerates a variety of functional groups and provides target amines in good to excellent yields.
High-level quantum electronic structure calculations are used to provide a deep insight into the mechanism and stereocontrolling factors of two recently developed catalytic asymmetric Diels–Alder ...(DA) reactions of cinnamate esters with cyclopentadiene. The reactions employ two structurally and electronically very different in situ silylated enantiopure Lewis acid organocatalysts: i.e., binaphthyl-allyl-tetrasulfone (BALT) and imidodiphosphorimidate (IDPi). Each of these catalysts activates only specific substrates in an enantioselective fashion. Emphasis is placed on identifying and quantifying the key noncovalent interactions responsible for the selectivity of these transformations, with the final aim of aiding in the development of designing principles for catalysts with a broader scope. Our results shed light into the mechanism through which the catalyst architecture determines the selectivity of these transformations via a delicate balance of dispersion and steric interactions.
The chemistry of preformed enamines, especially their use as enolate equivalents, has been a well-investigated area of research since the early 1950s. However, enamine catalysis, the catalysis of ...carbonyl transformations via enamine intermediates by using primary and secondary amines as catalysts, has only been fully appreciated as a powerful strategy for asymmetric synthesis since the beginning of this century. Contributions from this laboratory to the revitalized interest in asymmetric enamine catalysis are summarized in this Account.
Exceedingly high enantioselectivity in a catalytic reaction can be realized even when the chirality resides only in the counteranion of the catalyst. A salt (1) composed of an achiral ammonium cation ...and a chiral phosphate counteranion catalyzes asymmetric transfer hydrogenations of aromatic and aliphatic α,β‐unsaturated aldehydes with a Hantzsch ester in excellent enantioselectivities (see scheme).
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