Abstract:Palladium(II) trifluoroacetate (5 mol %) catalyzes the C-arylation of N,N-disubstituted hydantoins by aryl iodides in good yield. The reaction proceeds through base-promoted enolization of the amino acid derived hydantoins, and the resulting 5,5-disubstituted hydantoins may be deprotected at one or both N atoms to yield biologically active structures or alternatively hydrolyzed to the parent α-aryl α-amino acids. The reaction is successful with a variety of parent amino acids and a range of electron-rich and e… Show more
“…Clayden et al examined α-arylations of cyclic amino acids hydantoin derivatives (61a-61c) under the Pd(TFA) 2 /L-9 catalytic system using aryl iodides (62a-62c) as aryl sources. They found α-arylated products (63a-63e) could be obtained in good yields through ZnF 2 -mediated transmetallation (Scheme 26) [77].…”
“…Clayden et al examined α -arylations of cyclic amino acids hydantoin derivatives ( 61a-61c ) under the Pd(TFA) 2 / L-9 catalytic system using aryl iodides ( 62a-62c ) as aryl sources. They found α -arylated products ( 63a-63e ) could be obtained in good yields through ZnF 2 -mediated transmetallation (Scheme 26 ) [ 77 ]. Scheme 25 α -(sp 3 )-H arylations of oxazol-5-ones by Hartwig et al Scheme 26 α -(sp 3 )-H arylations of hydantoins reported by Claden et al …”
Abstractα-C(sp3)-H arylation is an important type of C-H functionalization. Various biologically significant natural products, chemical intermediates, and drugs have been effectively prepared via C-H functionalization. Cyclic carbonyl compounds comprise of cyclic ketones, enones, lactones, and lactams. The α-C(sp3)-H arylation of these compounds have been exhibited high efficiency in forming C(sp3)-C(sp2) bonds, played a crucial role in organic synthesis, and attracted majority of interests from organic and medicinal communities. This review focused on the most significant advances including methods, mechanism, and applications in total synthesis of natural products in the field of α-C(sp3)-H arylations of cyclic carbonyl compounds in recent years.
“…Clayden et al examined α-arylations of cyclic amino acids hydantoin derivatives (61a-61c) under the Pd(TFA) 2 /L-9 catalytic system using aryl iodides (62a-62c) as aryl sources. They found α-arylated products (63a-63e) could be obtained in good yields through ZnF 2 -mediated transmetallation (Scheme 26) [77].…”
“…Clayden et al examined α -arylations of cyclic amino acids hydantoin derivatives ( 61a-61c ) under the Pd(TFA) 2 / L-9 catalytic system using aryl iodides ( 62a-62c ) as aryl sources. They found α -arylated products ( 63a-63e ) could be obtained in good yields through ZnF 2 -mediated transmetallation (Scheme 26 ) [ 77 ]. Scheme 25 α -(sp 3 )-H arylations of oxazol-5-ones by Hartwig et al Scheme 26 α -(sp 3 )-H arylations of hydantoins reported by Claden et al …”
Abstractα-C(sp3)-H arylation is an important type of C-H functionalization. Various biologically significant natural products, chemical intermediates, and drugs have been effectively prepared via C-H functionalization. Cyclic carbonyl compounds comprise of cyclic ketones, enones, lactones, and lactams. The α-C(sp3)-H arylation of these compounds have been exhibited high efficiency in forming C(sp3)-C(sp2) bonds, played a crucial role in organic synthesis, and attracted majority of interests from organic and medicinal communities. This review focused on the most significant advances including methods, mechanism, and applications in total synthesis of natural products in the field of α-C(sp3)-H arylations of cyclic carbonyl compounds in recent years.
“…Many elegant methods have been established for the stereoselective synthesis of α-substituted derivatives starting from amino acids templates. [3] Furthermore, the synthetic methods for tetrasubstituted α-aryl amino acids mainly require the use of specialized metal catalysts (usually palladium, iron, rhodium, chromium, and copper based) [4] for enol-aryl coupling reactions. Other intriguing processes are conducted in the presence of an organometallic base and involving the functionalization of an amino acid through 'selfregeneration of chirality', [5] via Sommelet-Hauser rearrangement, [6] or adopting the Kawabata's principles of "memory of chirality" (MOC).…”
Herein we report a catalytic, easily scalable protocol for the enantioselective synthesis of Tetrasubstituted α‐aryl‐α‐amino acid derivatives, using a biphasic system composed by catalytic DBU in DME and aqueous solutions of Na2CO3. Under very mild reaction conditions, without using metal or chiral additives, this heterogeneous system promotes the degradative rearrangement of functionalized N‐aryl sulphonyl α‐amino esters into the corresponding tetrasubstituted 2‐aryl‐2‐amino esters, with high enantiomeric ratios (up to 97.5:2.5) and good yields (up to 95%).
“…This transformation proceeds by a concerted S N Ar mechanism, but the use of a urea tether to impose a conformational preference on the intermediate means that—unlike the classical Truce–Smiles rearrangement, which typically proceeds only with electron‐deficient aromatic rings—the electronic nature of the migrating aryl group is of little consequence to the outcome of the reaction . The N to C aryl migration that results has been developed into a versatile transition metal‐free route to a range of products including enantio‐enriched α‐quaternary amines, hydantoins, medium‐ring heterocycles, and α‐quaternary amino acids …”
We report tandem alkyl‐arylations and phosphonyl‐arylations of vinyl ureas by way of a photocatalytic radical‐polar crossover mechanism. Addition of photoredox‐generated radicals to the alkene forms a new C−C or C−P bond and generates a product radical adjacent to the urea function. Reductive termination of the photocatalytic cycle generates an anion that undergoes a polar Truce–Smiles rearrangement, forming a C−C bond. The reaction is successful with a range of α‐fluorinated alkyl sodium sulfinate salts and diarylphosphine oxides as radical precursors, and the conformationally accelerated Truce–Smiles rearrangement is not restricted by the electronic nature of the migrating aromatic ring. Formally the reaction constitutes an α,β‐difuctionalisation of a carbon–carbon double bond, and proceeds under mild conditions with visible light and a readily available organic photocatalyst. The products are α,α‐diaryl alkylureas typically functionalized with F or P substituents that may be readily converted into α,α‐diaryl alkylamines.
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