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A novel ruthenium-catalyzed alkenylative cyclization of enyne was developed. When an enyne was reacted with Cp*RuCl(cod) under an atmosphere of ethylene, ethylene was inserted into the ruthenium−sp2 carbon bond of ruthenacyclopentene derived from enyne and the low-valent ruthenium complex to afford ruthenacycloheptene, and β-hydrogen elimination followed by reductive elimination occurred to give a cyclic compound having a diene moiety. In this reaction, acrylaldehyde could be inserted into ruthenacyclopentene instead of ethylene. Various carbo- and heterocyclic compounds could be obtained in high yields.

The cyclodimerization of α,ω-allenynes using Cp*RuCl(cod) catalyst is described. This reaction proceeds via an alkylidene ruthenacyclopentene intermediate, which is generated by the oxidative cycloaddition of alkyne and the internal double bond of the allene, to give a unique pentacyclic compound having two five-membered rings and three four-membered rings in high yields.

Ruthenium-catalyzed cyclization of an enyne having a keto-carbonyl group on an alkyne under ethylene gas gave a cyclized compound with a cyclopropane ring on the substituent. Coordination of the carbonyl oxygen to a ruthenium metal of an intermediary ruthenacyclopentene is important and causes the formation of ruthenium carbene followed by construction of a cyclopropane ring by ethylene.

Rh(I)-catalyzed cycloisomerization of 1,3-dienes with alkenes in a tether proceeded smoothly, giving cyclopentene derivatives in good yields. It was interesting that the existence of a heteroatom between a 1,3-diene moiety and alkene in the tether affected the reaction course and that only a [4 + 2] cycloaddition product was produced.

The use of N-heterocyclic carbene 2 as a ligand in a nickel(0)-catalyzed coupling reaction of 1,3-diene and aldehyde was investigated. It was found that the Ni(0)−carbene complex showed a unique property in the reaction of 1,3-diene 4 and aldehyde 5 to give the coupling product Z-6, having a (Z)-olefin in high yield in a highly stereoselective manner. Since the same reaction using the Ni(0)−PPh3 complex gave E-6a in a stereoselective manner, this result indicates that the Ni(0)−carbene complex has a property different from that of the traditional Ni(0)−phosphine complex.

Enynes were reacted with Me3SiSnBu3 in the presence of Pd2dba3·CHCl3 or Pd(OH)2 on charcoal to give cyclized products containing a vinylsilane moiety and a homoallyltin moiety in good yield.

A transmetalation of the oxanickelacycle 7, generated from the 1,3-diene and tethered aldehyde in 6 via oxidative cycloaddition to a zerovalent nickel complex, with various organometallic reagents was investigated. It was found that the tandem reaction, i.e., cyclization of 6 followed by transmetalation of the resulting oxanickelacycle 7, proceeded smoothly using a catalytic amount of zerovalent nickel complex.