Transition metal-catalyzed arylation of unstrained C-C single bonds

Palladium-Catalyzed Synthesis of β-Alkynyl Ketones via Selective 1,3-Alkynyl Migration of α,α-Disubstituted Allylic Alcohols

Herein, a palladium-catalyzed 1,3-alkynyl migration of allylic alcohol for the synthesis of β-alkynyl ketone was described. This intramolecular rearrangement reaction demonstrated an enhanced reactivity compared to the traditional intermolecular alkynylation by circumventing the dimerization of alkynes, exhibiting a specific selectivity toward β-alkynyl elimination. Moreover, this reaction featured wide substrate scope, good functional group tolerance, and 100% atom economy.

Computational Exploration of 1,2-Carboamine Carbonylation Catalyzed by Nickel

Nickel-catalyzed carbonylation of alkenes is a stereoselective and regioselective method for the synthesis of amide compounds. Theoretical predictions with density functional theory calculations revealed the mechanism and origin of stereoselectivity and regioselectivity for the nickel-catalyzed carbonylation of norbornene. The carbonylation reaction proceeds through oxidative addition, migration insertion of alkenes, and subsequent reduction elimination to afford cis-carbonylation product. The C-N bond activation of amides is unfavorable because the oxidative addition ability of the C-C bond is stronger than that of the C-N bond. The determining step of stereoselectivity is the migratory insertion of the strained olefin. The structural analysis shows that steroselectivity is controlled by the steric hindrance of methyl groups to olefins and substituents to IMes in ligands.

Pd-Catalyzed Formal [2 + 2]-Retrocyclization of Cyclobutanols via 2-Fold Csp3-Csp3 Bond Cleavage

In this work, we describe the unexpected 2-fold Csp3-Csp3 bond cleavage suffered by cyclobutanols in the presence of a catalytic amount of Pd(OAc)2 and promoted by the bulky biaryl JohnPhos ligand. Overall, the sequential cleavage of a strained and an unstrained Csp3-Csp3 bond leads to the formal [2 + 2]-retrocyclization products, namely, styrene and acetophenone derivatives. This procedure might enable the use of cyclobutanols as masked acetyl groups, resisting harsh conditions in organic synthesis.

Rhodium-Catalyzed β-Acylalkylation of Allylbenzene Derivatives with Allyl Alcohols via C-C Bond Cleavage

We report here a deallylative β-acylalkylation reaction of allylbenzene derivatives with allyl alcohols in the presence of Cp*Rh catalysts. Allylbenzenes possessing pyridyl and pyrazolyl directing groups were converted to β-aryl ketones via the cleavage of C(aryl)-C(allyl) bonds. Synthesis of a quinoline derivative from a β-aryl ketone product bearing a pyrazolyl group was also achieved.

Late-Stage C(sp2 )-H Arylation of Artemisinic Acid and Arteannuin B: Effect of Olefin Migration Towards Synthesis of C-13 Arylated Artemisinin Derivatives

In recent years, C-H bond functionalization has emerged as a pivotal tool for late-stage functionalization of complex natural products for the synthesis of potent biologically active derivatives. Artemisinin and its C-12 functionalized semi-synthetic derivatives are well-known clinically used anti-malarial drugs due to the presence of the essential 1,2,4-trioxane pharmacophore. However, in the wake of parasite developing resistance against artemisinin-based drugs, we conceptualized the synthesis of C-13 functionalized artemisinin derivatives as new antimalarials. In this regard, we envisaged that artemisinic acid could be a suitable precursor for the synthesis of C-13 functionalized artemisinin derivatives. Herein, we report C-13 arylation of artemisinic acid, a sesquiterpene acid and our attempts towards synthesis of C-13 arylated artemisinin derivatives. However, all our efforts resulted in the formation of a novel ring-contracted rearranged product. Additionally, we have extended our developed protocol for C-13 arylation of arteannuin B, a sesquiterpene lactone epoxide considered to be the biogenetic precursor of artemisinic acid. Indeed, the synthesis of C-13 arylated arteannuin B renders our developed protocol to be effective in sesquiterpene lactone as well.

Decarbonylative cycloaddition of 1H-indene-1,2,3-trione and norbornene via rhodium(i)-catalyzed carbon–carbon bond cleavage

2,3-Dihydro-1H-inden-1-one derivatives were synthesized by a [5+2−2] decarbonylative cycloaddition of 1H-indene-1,2,3-trione and norbornene via rhodium(i) catalyzed direct carbon–carbon bond cleavage.