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Carbon dioxide is regarded as a reliable C1 building block in organic synthesis because of the nontoxic, abundant, and economical characteristics of carbon dioxide. In this manuscript, a commercially available oxovanadium(v) compound was demonstrated to serve as an efficient catalyst for the catalytic amination of carbon dioxide under ambient pressure in the synthesis of ureas. The catalytic transformation of chiral amines into the corresponding chiral ureas without loss of chirality was also performed. Furthermore, a gram-scale catalytic urea synthesis under ambient pressure was successfully achieved to validate the scalability of this catalytic activation of carbon dioxide.

Oxovanadium(V)-catalyzed transformation of alcohols in the presence of hydrazine derivatives was demonstrated. The direct hydrazination reaction of 1,3-diphenylprop-2-en-1-ol with 1,1-diphenylhydrazine in the presence of VO(OSiPh3)3 as a catalyst and MS3A as a dehydrating reagent proceeded to afford the corresponding hydrazination product. On the contrary, the utilization of 1,1-dimethylhydrazine instead of 1,1-diphenylhydrazine was found to induce the deoxygenative homocoupling reaction of the allyl alcohol to give the corresponding 1,5-diene as a major product. In addition to the deoxygenative homocoupling product, the allyl amine into which aniline was introduced was also obtained by using 1,2-diphenylhydrazine in the reaction of 1,3-diphenyl-2-methylprop-2-en-1-ol. Oxovanadium(V)-catalyzed deoxygenative homocoupling reaction of benzyl alcohols could also be performed in the presence of 1,1-dimethylhydrazine.

The (arylimido)vanadium(V) compound, [(p-MeOC6H4N)V(OiPr)3] was demonstrated to undergo ligand exchange reaction with one or two equivalents of 2,6-difluorophenol, affording the (arylimido)vanadium(V) compounds, [(p-MeOC6H4N)V(OiPr)2(O-2,6-F2Ph)] and [(p-MeOC6H4N)V(OiPr)(O-2,6-F2Ph)2]. Their X-ray crystallographic analyses elucidated the μ-isopropoxido-bridged dimeric structures, wherein each vanadium atom has a trigonal-bipyramidal arrangement with the imido and bridging isopropoxide ligands in the apical positions. The isopropoxide ligand was selectively employed as a bridging ligand between two central vanadium atoms. On the other hand, the reaction of the (arylimido)vanadium(V) compound, [(p-MeOC6H4N)VCl3] and three equivalents of lithium 2,6-difluorophenoxide gave the (arylimido)vanadium(V) compound, [(p-MeOC6H4N)V(O-2,6-F2Ph)3]. In the crystal packing, the thus-obtained compound showed a distorted trigonal-bipyramidal environment at the vanadium atoms with the μ-phenoxido-bridged dimeric structure, wherein the 2,6-difluorophenoxide ligand was found to serve as a bridging ligand.

(Diphenylhydrazido)vanadium(V) triisopropoxide was synthesized by the reaction of VO(OiPr)3 with N,N-diphenylhydrazine. The μ-isopropoxido-bridged dimeric structure was observed in the molecular structure of (diphenylhydrazido)vanadium(V) triisopropoxide. The near-linear V(1)-N(1)-N(2) angle of 173.7(3)° with the V(1)-N(1) distance of 1.667(4) A indicates that the imido nitrogen has large participation of an sp-hybridized character. The phenyl substituents of the hydrazido moiety were found to conjugate with the N−N bond. Furthermore, CH-π intermolecular interaction between two benzene rings was observed to induce polymeric structure in a solid state. (Diphenylhydrazido)vanadium(V) nitrilotriethoxide was obtained by the treatment of (diphenylhydrazido)vanadium(V) triisopropoxide with 2,2′,2′′-nitrilotriethanol. The slightly increased imido angle (V(1)-N(1)-N(2), 176.4(5)°) was observed as compared with (diphenylhydrazido)vanadium(V) triisopropoxide probably because of the apical coordination of the nitrogen.

(R)-(+)-1-Phenylethoxide ligands were introduced into (4-methoxyphenylimido)vanadium(V) or (dimethylhydrazido)vanadium(V) compound to afford the chiral vanadium(V) compounds with the V=N bond, wherein a chiral dimeric structure was formed in a crystalline state through the µ-alkoxido-bridging. Moreover, these chiral imido and hydrazido vanadium(V) compounds were demonstrated to dimerize by self-association at −80 °C even in a solution state.

The reaction of (1S,2S)-(-)-1,2-diphenylethylenediamine with VO(O

Correction for ‘Oxovanadium(v)-catalyzed amination of carbon dioxide under ambient pressure for the synthesis of ureas’ by Toshiyuki Moriuchi et al., RSC Adv., 2021, 11, 27121–27125. DOI: 10.1039/D1RA04125H.

Metal-free oxidative bromination reactions in aqueous media were performed using tetrabutylammonium bromide, trifluoroacetic acid, and hydrogen peroxide under mild conditions. Oxidative bromination reaction of alkenes was found to afford the corresponding vic-bromides. Furthermore, this oxidative bromination system is applicable to the oxidative bromination of alkynes, arenes, and 3,4-dihydronaphthalen-1(2H)-one. A gram-scale bromination reaction was also performed successfully.

The reaction of (1S,2S)-(−)-1,2-diphenylethylenediamine with VO(OiPr)3 in the presence of NaH was found to afford the binuclear (imido)vanadium(V) triisopropoxide, [(OiPr)3V(N-meso-1,2-DPE-N)V(OiPr)3] (DPE = diphenylethylene), (1aRS/SS). Using (1R,2R)-(+)-1,2-diphenylethylenediamine as a starting material, one-step reaction also proceeded to form the binuclear (imido)vanadium(V) triisopropoxide, [(OiPr)3V(N-meso-1,2-DPE-N)V(OiPr)3], (1aRS/RR). The single-crystal X-ray structure determination of 1aRS/SS revealed the hydrogen-bonded self-assembled structure utilizing the advantage of anti-conformation through the intermolecular hydrogen bonds of C-H···O pattern between phenyl and isopropoxide moieties, wherein each vanadium atom is coordinated in a nearly tetrahedral VO3N geometry (τ4 = 0.017 and 0.057). On the contrary, a discrete (imido)vanadium(V) tris(triphenylsiloxide) unit, which possesses a nearly tetrahedral VO3N arrangement around the vanadium metal center (τ4 = 0.060), was observed in the crystal structure of the (4-methoxyphenylimido)vanadium(V) tris(triphenylsiloxide), [(p-MeOC6H4N)V(OSiPh3)3], (1b) with bulky triphenylsiloxide ligands.

The vanadium(V) dimethylhydrazido compounds were structurally characterized to elucidate the effect of the alkoxide ligands in the coordination environment of vanadium(V) hydrazido center. The single-crystal X-ray structure determination of the vanadium(V) dimethylhydrazido compound with isopropoxide ligands revealed a dimeric structure with the V(1)-N(1) distance of 1.680(5)A, in which each vanadium atom is coordinated in a distorted trigonal-bipyramidal geometry (τ5=0.81) with the hydrazido and bridging isopropoxide ligands in the apical positions. On the contrary, nearly tetrahedral arrangement around the vanadium metal center (τ4=0.06) with the V(1)-N(1) distance of 1.660(2)A was observed in the vanadium(V) dimethylhydrazido compound with tert-butoxide ligands. The introduction of the 2,2',2″-nitrilotriethoxide ligand led to a pseudo-trigonal-bipyramidal geometry (τ5=0.92) at the vanadium center with the V(1)-N(1) distance of 1.691(5)A, wherein vanadium atom is pulled out of the plane formed by the nitrilotriethoxide oxygen atoms in the direction of the hydrazido nitrogen. The coordination from the apical ligand in the vanadium(V) dimethylhydrazido compound was found to result in the longer V(1)-N(1) distance.