Masahiro Murakami 교수

Reactions cleaving carbon-carbon bonds with the assistance of transition metals as the catalyst have provided various molecular transformations that are otherwise difficult to execute, opening a scenic avenue along organic synthesis. Construction of structural motifs like medium-sized carbocycles and chiral quaternary carbon centres have been set within an access of such paradoxical approaches in the past decade.

Conventional organic synthesis has been mainly based upon the reactivities of π-bonds and polar σ-bonds. Carbon-carbon single bonds are nonpolar and generally far less reactive. Although they remain intact under most reaction conditions, it is possible to activate and cleave them if suitable organometallic compounds or metal catalysts are applied. Such C-C single bond cleavage reactions are attracting increasing attention in the context of synthetic chemistry because they provide a unique and mo

This article reviews synthetic transformations involving cleavage of a carbon-carbon bond of a four-membered ring, with a particular focus on the examples reported during the period from 2011 to the end of 2019. Most significant is the progress of catalytic reactions involving oxidative addition of carbon-carbon bonds onto transition metals or β-carbon elimination of transition metal alkoxides. When they are looked at from synthetic perspectives, they offer unique and efficient methods to build

A directed cross-aldol reaction of silyl enol ethers with carbonyl compounds, such as aldehydes and ketones, promoted by a Lewis acid, a reaction which is now widely known as the Mukaiyama aldol reaction. It was first reported in 1973, and this year marks the 40th anniversary. The directed cross-aldol reactions mediated by boron enolates and tin(II) enolates also emerged from the Mukaiyama laboratory. These directed cross-aldol reactions have become invaluable tools for the construction of stere

Intramolecular insertion of a C-C double bond into a C-C single bond was achieved by treatment of cyclobutanone bearing an o-styryl group at the 3-position with a catalytic amount of a cationic rhodium(I)-dppp complex. Initially, rhodium is inserted between the carbonyl carbon and the alpha-carbon of the cyclobutanone. Intramolecular coordination of the vinyl group results in its migratory insertion into the C-Rh linkage. Reductive elimination affords benzobicyclo[3.2.1]octan-3-one. Notably, a r

Cyclobutanones reacted with alkynes in the presence of nickel(0) catalysts to produce cyclohexenones. Oxidative cyclization of the carbonyl group of the cyclobutanone and the alkyne with the nickel(0) was followed by beta-carbon elimination from the resulting oxanickelacyclopentene and subsequent reductive elimination. This reaction achieves a formal alkyne insertion between the carbonyl carbon and the alpha-carbon, providing a six-membered carbocyclic skeleton.

A study of rhodium(I)-catalyzed synthetic transformations involving selective breaking of the C−C bond α to the carbonyl group of cyclobutanones is described. Decarbonylation took place on treatment of a cyclobutanone with an equimolar amount of (Ph3P)3RhCl at reflux in toluene to afford the corresponding cyclopropane. The formation of the cyclopropane suggests that Rh(I) undergoes an insertion into the bond between the carbonyl carbon and the α-carbon in the initial step. Catalytic decarbonylat

Follow the guide: The palladium-catalyzed phosphonation of a C(sp2)H bond occurs through the use of a pyridyl group as the directing group. α-Hydroxyalkylphosphonate is used as the phosphonating reagent (see scheme).

Cyclobutanones underwent a formal [4 + 2 + 2] annulation reaction with 1,6- and 1,7-diynes in the presence of nickel(0) catalysts to provide bicyclic eight-membered ring ketones. The annulation reaction proceeds through a ring-expansion of oxanickelacycloheptadiene via beta-carbon elimination to form a nine-membered nickelacycle. This reaction employing cyclobutanones as a C4 unit constructs cyclooctadienone cores in one synthetic step.

In the nick of time: A nickel-catalyzed asymmetric intramolecular alkene insertion reaction into cyclobutanones (1) has been developed. The reaction significantly reduces the number of steps required for the synthesis of chiral benzobicyclo[2.2.2]octenones (2). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publishe

The C–C bond located at the β-position of an alkoxy radical readily breaks to form an alkyl radical along with a carbonyl compound. Such processes are called β-scission or β-fragmentation. They possibly proceed without any assistance of ring strain, and have recently attracted renewed attention as the key elementary step to transform alcohols in a unique fashion. Summarized in this Highlight Review are synthetic transformations of alcohols through β-scission of alkoxy radical intermediates. The

A palladium-catalyzed reaction of primary amines with iodoarenes produces γ-arylated primary amines. A bulky salicylaldehyde, which is marked as easily available, installable, removable, and recoverable, plays a key role in directing palladium to site-selectively activate the C-H bond located γ to the amino group.

A novel alkenylation reaction of pyridine is developed. Heating a cationic ruthenium vinylidene complex [CpRu(=C=CHR)(PPh(3))(2)]PF(6) in pyridine at 100-125 degrees C for 24 h affords (E)-2-alkenylpyridine. Initially, pyridine coordinates to ruthenium by displacement of one of the phosphine ligands. Then, [2 + 2] heterocycloaddition occurs to form a four-membered ruthenacyclic complex. Deprotonation of the beta-hydrogen affords a neutral pi-azaallyl complex. Protonolysis furnishes the product.