Yusuke Maegawa

Enzyme-like chemoselective acylation of alcohols in the presence of amines catalyzed by a tetranuclear zinc cluster.

Acylation of alcohols and amines is one of the most fundamental reactions. Due to the greater nucleophilicity of the amino group compared to the hydroxyl group, complete N-acylation occurs. Only an enzymatic reaction can promote a highly selective O-acylation reaction, and there are no examples using an artificial catalyst. Here we report that the tetranuclear zinc cluster Zn4(OCOCF3)6O efficiently catalyzes highly chemoselective O-acylation in the presence of primary and secondary alkyl amines. Our results suggest the high potential of the zinc cluster as the core structure of an artificial enzyme to realize further enzyme-like chemoselective reactions.

Transesterification of Various Methyl Esters Under Mild Conditions Catalyzed by Tetranuclear Zinc Cluster

A new catalytic transesterification promoted by a tetranuclear zinc cluster was developed. The mild reaction conditions enabled the reactions of various functionalized substrates to proceed in good to high yield. A large-scale reaction under solvent-free conditions proceeded with a low E-factor value (0.66), indicating the high environmental and economical advantage of the present catalysis.

A tetranuclear-zinc-cluster-catalyzed practical and versatile deprotection of acetates and benzoates

A new catalytic deacylation of acetates and benzoates through transesterification with methanol was developed (see scheme). Reactions with various acid- and nucleophile-sensitive functional groups proceeded efficiently in the presence of a catalytic amount of the tetranuclear zinc cluster. The present catalysis is applicable to less-reactive tertiary acetates, the deacylation of which is difficult to achieve by transesterification with other catalysts.

Selective Intermolecular Oxidative Cross-Coupling of Enolates.

Selective intermolecular oxidative cross-coupling of enolates, which is a bond-forming reaction between carbanion equivalents, remains as an unsolved issue despite its potential utility for the direct synthesis of unsymmetrical 1,4-diones. The main difficulty derives from the unavoidable homo-coupling. Our strategy depends on the selective one-electron oxidation of one enolate to afford an electrophilic carbonyl α-radical species, followed by trapping with another enolate. The present study demonstrates the selective oxovanadium(V)-induced cross-coupling between boron and silyl enolates.

Oxovanadium(V)-induced diastereoselective oxidative homocoupling of boron enolates

Oxovanadium(v)-induced dl-selective oxidative coupling of (Z)-boron enolate was demonstrated to give the corresponding 2,3-disubstituted 1,4-diketone in a good yield. High selectivity (up to 94 : 6) was attained when the reaction was performed with VO(OPr-i)2Cl at -30 °C.

Vanadium(V)‐Induced Oxidative Cross‐Coupling of Various Boron and Silyl Enolates

Intermolecular oxidative cross-coupling of two different enolates is one of the most useful reactions to synthesize unsymmetrical 1,4-dicarbonyl compounds. In this study, the oxovanadium(V)-induced intermolecular oxidative cross-coupling of enolates afforded unsymmetrical 1,4-dicarbonyl compounds. Various boron and silyl enolates underwent the formation of ketone-ester, ester-ketone, ester-ester, amide-ketone and amide-ester coupling products . These results clearly show the versatility of the present oxidative cross-coupling protocol.