Palladium-catalyzed asymmetric arylation, vinylation, and allenylation of tert-cyclobutanols via enantioselective C-C bond cleavage

α,β-Diaryl unsaturated ketones via palladium-catalyzed ring-opening of cyclopropenones with organoboronic acids

Palladium-catalyzed ring-opening acylation of cyclopropenones with organoboronic acids (aryl and vinylboronic acids) at room temperature has been developed to synthesise α,β-diaryl unsaturated ketones with good yields and excellent stereospecificity.

Acyclic Quaternary Carbon Stereocenters via Enantioselective Transition Metal Catalysis

Whereas numerous asymmetric methods for formation of quaternary carbon stereocenters in cyclic systems have been documented, the construction of acyclic quaternary carbon stereocenters with control of absolute stereochemistry remains a formidable challenge. This Review summarizes enantioselective methods for the construction of acyclic quaternary carbon stereocenters from achiral or chiral racemic reactants via transition metal catalysis.

A β-Carbon elimination strategy for convenient in situ access to cyclopentadienyl metal complexes

The electronic and steric properties of tailored cyclopentadienyl (Cp) ligands are powerful handles to modulate the catalytic properties of their metal complexes. This requires the individual preparation, purification and storage of each ligand/metal combination. Alternative, ideally in situ, complexation protocols would be of high utility. We disclose a new approach to access Cp metal complexes. Common metal precursors rapidly react with cyclopentadienyl carbinols via β-carbon eliminations to directly give the Cp-metal complexes. An advantage of this is the direct and flexible use of storable pre-ligands. No auxiliary base is required and the Cp complexes can be prepared in situ in the reaction vessel for subsequent catalytic transformations.

Cu-Mediated Rearrangements of Allenylcyclopropanols to Cyclopentenones: Two Divergent Pathways

Two CuCN-mediated rearrangement reactions of allenylcyclopropanols to cyclopentenones have been achieved by means of Et₂Zn/CuCN·2LiCl or CuCN·2LiCl to afford 5-alkyl or 4-alkyl cyclopentenone regioisomers: the former conditions afford 5-alkyl substituted cyclopentenones via β-carbon elimination, whereas the latter result in the 4-alkyl substituted regioisomers with concomitant oxidation at the γ-position, via a free radical mechanism.

Recent Methodologies That Exploit C-C Single-Bond Cleavage of Strained Ring Systems by Transition Metal Complexes

In this review, synthetic and mechanistic aspects of key methodologies that exploit C-C single-bond cleavage of strained ring systems are highlighted. The focus is on transition-metal-catalyzed processes that are triggered by C-C bond activation and β-carbon elimination, with the review concentrating on developments from mid-2009 to mid-2016.

Ring-opening selenation of cyclobutanols: synthesis of γ-selenylated alkyl ketones through C–C bond cleavage

An efficient, practical, and operationally simple manganese-mediated ring-opening selenation of cyclobutanols is disclosed.

Copper-catalyzed transformation of ketones to amides via C(CO)–C(alkyl) bond cleavage directed by picolinamide

Copper catalyzed chemoselective cleavage of the C(CO)–C(alkyl) bond leading to C–N bond formation with chelation assistance of N-containing directing groups is described.

Palladium-Catalyzed Enantioselective Redox-Relay Heck Arylation of 1,1-Disubstituted Homoallylic Alcohols

An enantioselective redox-relay oxidative Heck arylation of 1,1-disubstituted alkenes to construct β-stereocenters was developed using a new pyridyl-oxazoline ligand. Various 1,2-diaryl carbonyl compounds were readily obtained in moderate yield and good to excellent enantioselectivity. Additionally, analysis of the reaction outcomes using multidimensional correlations revealed that enantioselectivity is tied to specific electronic features of the 1,1-disubstituted alkenol and the extent of polarizability of the ligand.

Manganese-Promoted Ring-Opening Hydrazination of Cyclobutanols: Synthesis of Alkyl Hydrazines

We herein disclose an efficient manganese-promoted hydrazination of cyclobutanols through cyclic C-C bond cleavage. The ring opening occurs under mild reaction conditions, readily affording a variety of alkyl hydrazines in synthetically useful yields and exclusive regioselectivities. The chain reaction mechanism involving the addition of alkyl carbon radical to azodicarboxylate is proposed.

Z-Selective Synthesis of γ,δ-Unsaturated Ketones via Pd-Catalyzed Ring Opening of 2-Alkylenecyclobutanones with Arylboronic Acids

Pd-catalyzed 1,2-addition (instead of 1,4-addition) of arylboronic acids to 2-alkylenecyclobutanones followed by β-carbon elimination from the resulting palladium cyclobutanolates to afford γ,δ-unsaturated ketones was developed. The desired γ,δ-unsaturated ketones were obtained in good to excellent yields with Z/E selectivities of up to >99:1 and a broad spectrum of functional group tolerability.

Silver-mediated oxidative trifluoromethylthiolation of cycloalkanols by C–C bond cleavage: a regioselective approach to distally trifluoromethylthiolated ketones

Various distally trifluoromethylthiolated ketones were readily prepared by silver-mediated oxidative trifluoromethylthiolation of cycloalkanols. The reaction features complete regioselectivity, operational simplicity, and excellent practicality.

Manganese-catalyzed regiospecific sp3C–S bond formation through C–C bond cleavage of cyclobutanols

A manganese-catalyzed regioselective sp³C–S bond formation through C–C bond cleavage of cyclobutanols is described.

Manganese-catalyzed ring-opening chlorination of cyclobutanols: regiospecific synthesis of γ-chloroketones

An efficient, mild, and practical ring-opening chlorination of cyclobutanols is developed by means of manganese catalysis.

Enantioselective syntheses of indanes: from organocatalysis to C–H functionalization

The indanyl core is ubiquitous in a large variety of drugs and natural products. Remarkable recent progress has been accomplished in the step-economical assembly of functionalization of chiral indanes by means of enantioselective catalysis, with major progress being achieved in organocatalysis and C–H activation chemistry.

Palladium–copper catalyzed C(sp3)–C(sp2) bond C–H activation cross-coupling reaction: selective arylation to synthesize 9-aryl-9H-xanthene and 9,9-diaryl-xanthene derivatives

A novel palladium–copper catalyzed C(sp³)–C(sp²) bond C–H activation cross-coupling reaction has been developed. A series of 9-aryl-9H-xanthenes and 9,9-diaryl-xanthenes were selectively synthesized in moderate to good yields by controlling the reaction time and temperature.

Construction of Enantiopure Taxoid and Natural Product-like Scaffolds Using a C-C Bond Cleavage/Arylation Reaction

An approach to construct enantiopure complex natural product-like frameworks, including the first reported synthesis of a C17 oxygenated taxoid scaffold, is presented. A palladium-catalyzed C-C activation/cross-coupling is utilized to access these structures in a short sequence from (+)-carvone; the scope of this reaction is explored.

Highly enantioselective rhodium(I)-catalyzed carbonyl carboacylations initiated by C-C bond activation

The lactone motif is ubiquitous in natural products and pharmaceuticals. The Tishchenko disproportionation of two aldehydes, a carbonyl hydroacylation, is an efficient and atom-economic access to lactones. However, these reaction types are limited to the transfer of a hydride to the accepting carbonyl group. The transfer of alkyl groups enabling the formation of CC bonds during the ester formation would be of significant interest. Reported herein is such asymmetric carbonyl carboacylation of aldehydes and ketones, thus affording complex bicyclic lactones in excellent enantioselectivities. The rhodium(I)-catalyzed transformation is induced by an enantiotopic CC bond activation of a cyclobutanone and the formed rhodacyclic intermediate reacts with aldehyde or ketone groups to give highly functionalized lactones.

Highly enantioselective rhodium(I)-catalyzed activation of enantiotopic cyclobutanone C-C bonds

The selective functionalization of carbon-carbon σ bonds is a synthetic strategy that offers uncommon retrosynthetic disconnections. Despite progress in C-C activation and its great importance, the development of asymmetric reactions lags behind. Rhodium(I)-catalyzed selective oxidative additions into enantiotopic C-C bonds in cyclobutanones are reported. Even operating at a reaction temperature of 130 °C, the process is characterized by outstanding enantioselectivity with the e.r. generally greater than 99.5:0.5. The intermediate rhodacycle is shown to react with a wide variety of tethered olefins to deliver complex bicyclic ketones in high yields.