Bridged biaryl atropisomers are important units in bioactive molecules. A synthesis of lactone-bridged biaryl atropisomers was realized by a Cu-catalyzed asymmetric ring-opening/acyoxylation of ...cyclic diaryliodoniums, followed by a palladium-catalyzed diastereoselective cyclization. It was found that a catalytic amount of Cu(OTf)2 served as an additive to promote the palladium-catalyzed Heck cyclization.
An efficient palladium‐catalyzed asymmetric synthesis of axially chiral vinyl arenes from aryl bromides and hydrazones is reported. The products were easily oxidized to axially chiral biaryl ...compounds, and the phosphine oxides were readily reduced to phosphine ligands.
With a twist: An enantioselective palladium‐catalyzed synthesis of atropisomeric vinyl arenes from aryl bromides and hydrazones is reported. The use of hydrazone precursors as coupling partners resulted in mild reaction conditions, and thus a broad functional‐group tolerance. The products were isolated with ee values of up to 97 %. Ts=4‐toluenesulfonyl.
Abstract
Atropisomers are important organic frameworks in bioactive natural products, drugs as well as chiral catalysts. Meanwhile, silanols display unique properties compared to their alcohol ...analogs, however, the catalytic synthesis of atropisomers bearing silanol groups is challenging. Here, we show a rhodium-catalyzed torsional strain-promoted asymmetric ring-opening reaction for the synthesis of α-silyl biaryl atropisomers. The reaction features a dynamic kinetic resolution of C(Ar)-Si bond cleavage, whose stereochemistry was controlled by a phosphoramidite ligand derived from (
S
)-3-methyl-1-((2,4,6-triisopropylphenyl)sulfonyl)piperazine. This work is a demonstration of an aryl-Narasaka acylation, where the C(Ar)-Si bond cleavage is promoted by the torsional strain of α, α’-disubstituted silafluorene.
A Cu-catalyzed asymmetric ring-opening reaction of five-membered diaryliodonium salts and oximes is introduced. The reactions undergo selective N-arylation of oximes and provide an efficient protocol ...for the synthesis of atropisomeric nitrones. The optically active nitrones, serving as versatile intermediates, were converted to diversely functionalized axially chiral aniline derivatives and N-heterocycles.
The palladium‐catalyzed asymmetric synthesis of enone‐based atropisomers from 2‐iodo‐3‐methylcyclohex‐2‐enones and aryl boronic acid is reported. BoPhoz‐type phosphine–aminophosphine ligands showed ...superior enantioselectivity over other ligands. These cyclohexenone‐based atropisomers are useful compounds for further elaboration. The divergent synthesis of biaryl atropisomers with different ortho substituents was demonstrated.
A platform to improve the outlook: The palladium‐catalyzed asymmetric coupling of 2‐iodo‐3‐methylcyclohex‐2‐enones and aryl boronic acids provided axially chiral enone–arene systems with several potential sites for further transformation (see scheme). In particular, these cyclohexenone‐based atropisomers serve as a valuable platform for the synthesis of biaryl atropisomers with different ortho substituents.
A Cu-catalyzed enantioselective desymmetrizing ring-opening reaction of six-membered cyclic diaryliodonium salts with carboxylic acids or thioacids is reported for the facile access to chiral ...diarylmethanes. A Cu/cyclopropyl bis(oxazoline) catalyst well discriminates two C–I bonds of prochiral cyclic diaryliodonium salts. A stereochemical model was proposed to rationalize the stereochemical outcome on the basis of the crystal structure of cyclic diaryliodonium salt.
A preparation of 2-hydroxyamino-2′-iodobiaryls via the Cu-catalyzed enantioselective ring-opening reaction of cyclic diaryliodonium salts with O-alkylhydroxylamines is reported. ...3,5-Di(tert-butyl)phenyl bis(oxazoline) was found to be the optimal ligand, and up to 99% ee values were achieved. The use of CaO as the base dramatically improved the yields and inhibited the side reactions. Finally, synthetic applications of these hydroxylamines were briefly demonstrated.
Generation of carbon‐metal species is extremely important in transition metal‐catalyzed organic synthesis. Among the various methods, 1,4‐metal migration is a very useful way to create new ...carbon‐metal species, which are not readily accessible via classic methods. This review summarized recent advances in transition metal‐catalyzed reactions, which involved one or more steps of 1,4‐metal migration. It focused mostly on the achievements in Pd and Rh‐catalyzed reactions, along with some of the remarkable results in Pt, Ir, Co, Fe‐involved transformations.
The 1,4‐metal migration is a very useful way to create new carbon‐metal species, which are pivotal in transition metal‐catalyzed transformations. This review summarized the recent advances in transition metal‐catalyzed reactions, which at least contained one step of 1,4‐metal migration.
A transition‐metal‐free synthesis of spiro compounds from 9H‐fluoren‐9‐ols mediated by hypervalent iodine is reported. In this reaction, an unprecedented β‐carbon elimination of tertiary ...alkoxyliodine(III) to form new diaryliodonium salts is proposed. The obtained phenol intermediates undergo oxidative dearomatization to furnish a class of oxo‐spiro compounds. This domino reaction significantly increases the complexity of these molecules and shows excellent regio‐ and stereoselectivity.
The best things come with iodine(III): A carbon–carbon bond cleavage reaction of 9H‐fluoren‐9‐ols mediated by hypervalent iodine(III) is reported. The reaction continues with reductive elimination and dearomatization. A class of spiro compounds were synthesized in a highly efficient and stereoselective manner.
A total synthesis of the unusual ent-kaurane maoecrystal V is described. The synthesis strategy features a counterintuitive early disconnection of the lactone subunit to a polycyclic enol ether ...intermediate in order to preserve the central tetrahydrofuran ring until the beginning stages of the synthesis. This strategy enables an application of C–H functionalization at the early phase of the synthesis during the construction of a dihydrobenzofuran intermediate.
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