A new efficient synthetic route to unsymmetrically substituted dihydropyridine scaffolds via dehydrative [4 + 2] cycloaddition of N-tosylated α,β-unsaturated imines with aldehydes has been developed. This transformation is enabled by (i) the remarkable catalytic ability of the cationic Ru(IV) porphyrin complex to activate both the imino and carbonyl groups and (ii) the hydrophobic nature of the porphyrin ligand, which helps realize robust Lewis acidity in the dehydrative cycloaddition.

A nickel/Lewis acid catalyzed intermolecular cycloaddition reaction of o-cyanobenzylarylketones with alkynes to form naphthalenones is developed. This reaction is promoted by the nickel/Lewis Acid catalyst pair and involves the cleavage of two C–C σ bonds to eliminate arylcyanide and the formation of different two C–C σ bonds with alkyne insertion.

We have developed a redox-economical coupling reaction of alcohols and alkynes to form allylic alcohols under mild conditions. The reaction is redox-neutral as well as redox-economical and thus free from any additives such as a reductant or an oxidant. This atom-economical coupling can be applied for the conversion of both aliphatic and benzylic alcohols to the corresponding substituted allylic alcohols in a single synthetic operation.

A new synthetic method for thiochromones was developed by using nickel-catalyzed decarbonylative cycloaddition of readily available thioisatins with alkynes. This reaction proceeded under very mild conditions and has quite high functional group compatibility.

Lewis acid catalyzed cycloaddition of cyclohexenone and butadiene affords trans-fused octalone with high regio- and diastereoselectivity. The use of the ruthenium porphyrin complex as the Lewis acid catalyst is key to the reaction. The cycloaddition proceeds in toluene with 1 mol % of the ruthenium catalyst at 25 °C.

We have developed a nickel-catalyzed transformation, in which phthalimides react with trimethylsilyl-substituted alkynes in the presence of Ni(0)/PMe3/MAD catalyst to provide isoindolinones. The reaction process displays an unusual mechanistic feature—decarbonylation and alkylidenation. The use of both trimethylsilyl-substiuted alkynes and MAD was found to be essential for the transformation with high selectivities.

Nickel-catalyzed intermolecular [3 + 2] cycloaddition of vinylcyclopropanes to imines has been developed. This transformation generates substituted pyrrolidines in high yields, with good regio- and diastereo- selectivity under mild reaction conditions. A variety of imines can be used in this reaction. An asymmetric variant of the reaction has also been demonstrated.

Substituted quinolones were efficiently synthesized via the nickel-catalyzed cycloaddition of o-cyanophenylbenzamide derivatives with alkynes. The reaction involves elimination of a nitrile group by cleavage of the two independent aryl–cyano and aryl–carbonyl C–C bonds of the amides.

Cycloisomerization of 1,6-enynes is successfully carried out in the presence of a dicationic platinum(IV) catalyst to afford five-membered ring systems. The use of a weakly coordinating axial ligand is the key to bringing out the catalytic activity of platinum porphyrin for the reaction.

An efficient protocol for the aza-Diels–Alder reaction of electron-deficient 1,3-dienes with unactivated imines in the presence of a cationic cobalt(III) porphyrin complex was developed. The transformation proceeded smoothly to afford the desired piperidine scaffold within 2 h at ambient temperature. Highly chemoselective cycloaddition of imines with dienes in the presence of a variety of carbonyl compounds was also demonstrated.