Ozonolysis of 18α-Oleanane triterpenoid with an alkenenitrile moiety in the five-membered ring A

A novel synthetic protocol of ozonolytic cleavage of 18α-oleanane triterpenoid with the five-membered α,β-alkenenitrile moiety dissolved in dichloromethane to selectively synthesize a 1,3-secotriterpene derivative with 78% yield was developed. Spontaneous condensations of the synthesized 19β,28-epoxy-1,3-seco-2-nor-18α-olean-3-al-1-oic acid followed by formation of unsubstituted 1,3- and 1,4-lactones were registered in reactions with sodium borohydride as a reducing reagent or oxalyl chloride as an activating agent, respectively. α-Methoxy- and α-ethoxy-substituted 1,3-lactones were obtained when the polar protic solvents methanol or ethanol were used for the ozonolysis of the alkenenitrile. Experiments on ozonolysis were carried out in combination with reduction with dimethyl sulfide. Ozonolysis of alkenenitrile in dichloromethane without reductive treatment was found out to have resulted in stable triterpene ozonide.     

Complexes formed by the reactions of fluorinated and non-fluorinated organonitriles with [Zn(SO2)2][AsF6]2: A structural study

[Zn(SO₂)₂][AsF₆]₂ (1) has been prepared from zinc metal and AsF₅ in liquid sulfur dioxide, and crystallized from sulfur dioxide giving crystals of [Zn(SO₂)₄(AsF₆)₂] (1a). The compound 1 forms the homoleptic complexes [Zn(NCR)₆](AsF₆)₂ (R: CH₃ (2a), C₆H₅ (3a), C₆F₅ (3b)) with the corresponding nitriles. In these complexes, the metal center is octahedrally surrounded by six ligands (average Zn–N 2.13 ?). Reaction of 1 with the weaker ligand F₃CCN results in dicoordination at the metal center complemented by a two-dimensional polymeric network (2b) containing bridging AsF₆ ⁻ anions. [Zn(SO₂)₄(AsF₆)₂] (1a): monoclinic, P2₁/c, a=8.5176(8) ?, b=13.5787(14) ?, c=14.7661(15) ?, β=99.296(2)°; [Zn(NCCH₃)₆][AsF₆]₂ (2a): rhombohedral, R-3, a=11.2225(8) ?, b=11.2225(8) ?, c=16.9393(14) ?; [Zn (NCCF₃)₂][μ-FAsF₅)₂( (2b): monoclinic, P2₁/c, a=11.226(3) ?, b=6.6147(19) ?, c=10.460(3) ?, β=104.028(5)°; [Zn(NCC₆H₅)₆][AsF₆]₂ (3a): monoclinic, P2₁/n, a=13.7968(10) ?, b=19.8861(15) ?, c=16.1692(12) ?, β=91.563(2)°; [Zn(NCC₆F₅)₆][AsF₆]₂·2SO₂ (3b): monoclinic, P2₁/n, a=10.8448(9) ?, b=154456(13) ?, c=17.5206(15) ?, β=104.158(1)°.     

A new one-pot neat synthesis of 1,2,4-triazol-3-ones through 4-(N, N-dimethylamino) pyridine (DMAP) catalyzed cyclocondensation of ethyl carbazate with aryl nitriles

A new one-pot neat synthesis of some 5-aryl-2,4-dihydro-3H-1,2,4-triazol-3-ones through cyclocondensation of ethyl carbazate with aryl nitriles catalyzed by DMAP as an efficient and basic nucleophilic catalyst is described.     

Switchable C- and N-bound isomers of transition-metal cyanocarbanions: synthesis and interconversions of cyclopentadienyl ruthenium complexes of phenylsulfonylacetonitrile anions

The synthesis, structure, and dynamic behavior of bistable C- and N-bound isomers of transition-metal cyanocarbanions are described. A series of C-bound cyclopentadienyl (Cp) ruthenium phosphane complexes, [Ru{CH(CN)SO2Ph}(Cp)L1L2] (3), and their N-bound isomers, [Ru+(Cp)(NCCH(-)SO2Ph)L1L2] (4), were prepared by treating [RuCl(Cp)(PR3)2] with the sodium salt of phenylsulfonylacetonitrile and performing ligand-exchange reactions with the resulting compounds. Structural characterization by X-ray diffraction indicates that the cyanocarbanion moiety of 3 has an alpha-metalated structure, whereas that of 4 has a zwitterionic, end-on structure. Heating these complexes in aprotic solvents gives rise to irreversible linkage isomerization between C- and N-bound isomers, in which the relative thermal stabilities vary greatly depending on the steric and electronic nature of the ligands. Mechanistic studies of N-to-C isomerization revealed that the reaction proceeds irreversibly in a unimolecular manner without the formation of coordinatively unsaturated species. A metal-sliding process, which occurs over the -C-C triple chemical bond N pi-conjugated surface of the cyanocarbanion moiety, was suggested by results from kinetic studies and density functional theory (DFT) calculations. C-to-N isomerizations proceed by the above-mentioned intramolecular process, with a temperature-dependent contribution from the formation and cleavage of mu2-C,N coordination dimers [{Ru{CH(CN)SO2Ph}(Cp)(PPh3)}2] (15 and 16).