Palladium-catalyzed Enantio- and Regioselective Ring-Opening Hydrophosphinylation of Methylenecyclopropanes

Transition metal-catalyzed hydrofunctionalization of methylenecyclopropanes (MCP) has presented a considerable challenge due to the difficult manipulation of regioselectivity and complicated reaction patterns. Herein, we report a straightforward Pd-catalyzed ring-opening hydrophosphinylation reaction of MCP via highly selective C-C bond cleavage. This allows for rapid and efficient access to a wide range of chiral allylic phosphine oxides in good yields and high enantioselectivities. Additionally, density functional theory (DFT) calculations were performed to elucidate the reaction mechanism and the origin of product enantioselectivity.

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.

Rapid construction of cyclopenta[b]naphthalene frameworks from propargylic alcohol tethered methylenecyclopropanes

We have developed a new synthetic methodology for the rapid construction of cyclopenta[b]naphthalene frameworks from the reaction of propargylic alcohol tethered methylenecyclopropanes with mesyl chloride in the presence of triethylamine through cascade cyclization. The reaction can be performed under mild conditions without the use of transition metals, affording the target products in moderate to good yields, and this cyclization reaction process can be scaled up to a gram-scale synthesis.

A highly efficient method for the construction of cyclopropane-containing dihydroindole derivatives from indolemethylenecyclopropanes with DIAD and DEAD

A highly efficient method for the construction of cyclopropane-containing dihydroindole derivatives from indolemethylenecyclopropanes with DIAD and DEAD has been disclosed. The transformation could occur under catalyst-free conditions at ambient temperature to afford dihyroindole derivatives in good yields. It has been proved that the strained moiety of methylenecyclopropane in the substrate of indolemethylenecyclopropane is critical and DFT calculations reveal that the reaction proceeds through a two-step pathway.

Lewis or Brønsted acid-catalysed reaction of propargylic alcohol-tethered alkylidenecyclopropanes with indoles and pyrroles for the preparation of polycyclic compounds tethered with indole or pyrrole motif

We developed a facile synthetic method to access the cyclopenta[b]naphthalene skeleton from Lewis or Brønsted acid-catalysed propargylic alcohol-tethered alkylidenecyclopropanes with indole and pyrrole derivatives.

Mechanistic insights into Pd(0)-catalyzed intermolecular and intramolecular hydroamination of methylenecyclopropanes: a computational study

The mechanisms of transition metal-catalyzed methylenecyclopropanes (MCPs)-involved reactions are rather complicated due to the diverse pathways for the activation of MCPs. Herein, computational studies were carried out to investigate the detailed mechanisms of Pd(0)-catalyzed intermolecular and intramolecular hydroamination of MCPs. The initial activation of the three-membered ring of MCPs readily occurs via the insertion of Pd(0) into the distal C-C bond, leading to a metallacyclobutane intermediate. The commonly proposed oxidative addition of amine/amide nucleophile (Nu-H) onto the Pd(0) center to afford a hydrido-Pd(ii) complex, however, is less favorable in comparison with the Pd(0)-mediated cleavage of the distal C-C bond of MCPs. Subsequently, for the Pd(0)-catalyzed intermolecular hydroamination of 1,1-diphenyl MCP with 2-pyrrolidone, it is more favorable for the C1 of the metallacyclobutane intermediate to undergo protonation to yield a π-allylpalladium intermediate, from which the final allylamine product is afforded via reductive elimination. For the Pd(0)-catalyzed intramolecular hydroamination of aniline-tethered MCP, the intramolecular nucleophilic attack of the amine moiety to C3/C4 of the corresponding metallacyclobutane intermediate is preferable to generate a cyclic intermediate. Subsequent proton transfer steps could occur to complete the hydroamination reaction. The different pKa values of the N-H bonds of amide/amine are mainly responsible for the mechanistic difference in the Pd(0)-catalyzed hydroamination of MCPs.

Rhodium-catalyzed decarbonylative cycloadditions of 1H-indene-1,2,3-triones and alkynes via direct C–C bond activation: divergent synthesis of indenones and quinones

A one-step preparation method for indenone and quinone derivatives via rhodium-mediated [5 + 2 − 2] and [5 + 2 − 1] decarbonylative cycloadditions of 1H-indene-1,2,3-triones and alkynes has been achieved.