Cyclisation reactions of bis-protected guanidines

The cyclisation of N-allyl- and N-homoallylguanidines using DMDO or I₂/K₂CO₂ leading to novel heterocycles is reported.     

One-pot synthesis of a novel C1-symmetric diphosphine from 1,3-cyclic sulfate. Asymmetric hydroformylation of styrene

Preparation of a novel homochiral diphosphine with C₁-symmetry from the cyclic sulfate of (2R,4R)-2,4-pentanediol is reported. Reaction of a lithium phosphide salt with the cyclic sulfate affords a γ-phospholylsulfate which can be converted to a diphosphine ligand on treatment with a second equivalent of lithium phosphide. Using this ligand in the platinum-catalyzed asymmetric hydroformylation of styrene, outstanding levels of regio- and enantiocontrol were obtained (89/11 iso/n isomeric ratio and 89% e.e.). The results are compared with those obtained with the analogous ligands (bdpp and bdbpp) having C₂-symmetry. The novel unsymmetric ligand possessed the advantageous catalytic features of the C₂-symmetric parent ligands.     

A novel combination of (diacetoxyiodo)benzene and tert-butylhydroperoxide for the facile oxidative dehydrogenation of 3,4-dihydropyrimidin-2(1H)-ones

A clean and efficient oxidative dehydrogenation of 3,4-dihydropyrimidin-2(1H)-ones to 1,2-dihydropyrimidines has been achieved through a novel combination of (diacetoxyiodo)benzene and tert-butylhydroperoxide in CH₂Cl₂.     

A simple, novel and convenient method for the synthesis of 1-aminophosphinic acids: synthesis of a novel C2-symmetric phosphinic acid pseudodipeptide

A simple, efficient and novel method has been developed for the synthesis of 1-aminophosphinic acids from simple starting materials. Treatment of aromatic aldehydes with ammonia and hypophosphorus acid gives novel C₂-symmetric 1-aminoarylmethylphosphinic acids. The synthesis of novel C₂-symmetric phosphinic acid pseudodipeptides is also discussed.     

Hydrothermal synthesis and structure of an unprecedented layered Cd-citrate complex containing helical chains

An exploration of the cadmium-citrate system under hydrothermal conditions, has led to the isolation of a novel framework [Cd₃(H₂O)₂(C₆H₅O₇)₂]_n1. This compound features a novel 2D undulated sheet containing infinite double-stranded helical chains, which is unique among metal-citrate system identified so far. Crystal data for compound 1: Monoclinic, Space group P2₁/c, a=6.0974(12)  Å, b=15.271(3) Å, c=9.781(2) Å, β=102.74(3)°, V=888.3(3) Å³, Z=2. Other characterizations by elemental analysis, IR and TG are also described.     

An iminophosphine dendrimeric ligand and its evaluation in the Heck reaction

DAB-dendr-(NH₂)₃₂ has been modified to produce two novel dendrimeric P,N-ligands, DAB-dendr-[1,2-(NCHC₆H₄PPh₂)]₃₂ and DAB-dendr-[1,2-(NHCH₂C₆H₄PPh₂)]₃₂. These were both found to activate electron rich aryl bromides in the Heck reaction. The reactions seem to proceed better in a novel solvent system consisting of an equimolar mixture of a tertiary amine with acetic acid. A marked dependence of the conversion on the [equivalents of dendrimeric ligand]/[Pd] ratio has been observed with conversion decreasing as the ratio of dendrimer equivalents to Pd increases. This phenomenon is attributed to interactions of the arms bearing the metal with neighboring ones within the dendrimer.     

Ring opening of 2-(cyanomethyl)aziridines by acid chlorides: synthesis of novel 4-amino-2-butenenitrile derivatives through intermediate aziridinium salts

1-Arylmethyl-2-(cyanomethyl)aziridines were transformed into novel N-arylmethyl-N-(2-chloro-3-cyanopropyl)amides as the major reaction products upon treatment with acid chlorides in CH₂Cl₂ through the ring opening of intermediate aziridinium salts. Subsequently, N-arylmethyl-N-(2-chloro-3-cyanopropyl)amides were converted into stable N-arylmethyl-N-(3-cyano-2-propenyl)amides for the first time by means of a dehydrochlorination mediated by Et₃N in CH₂Cl₂.     

Synthesis, structure and photochromic properties of a novel 1,6-hexanediamine trimolybdate supramolecular compound

A novel supramolecular compound 1,6-hexanediamine trimolybdate ((C₆H₁₈N₂)[Mo₃O₁₀], denoted as HDAMo) has been synthesized by a hydrothermal method and its structure has been characterized by elemental analyses, Fourier transform infrared (FT-IR) spectra, single-crystal X-ray diffraction (XRD) technique. This single crystal compound consists of protonated 1,6-hexanediamine (HDA) cations and polyoxometalate [Mo₃O₁₀]²⁻ anions. Its crystal structure belongs to monoclinic system (space group P2₁/n) with a=7.7508(14), b=11.467(2), c=16.167(3) Å, β=92.689(3)°, V=1435.3(5) Å³, Z=4 and D_calc=2.619 g cm⁻³. The final statistics based on F² are GOF=0.980, R₁=0.0261 and wR₂=0.0506 for I>2σ(I). XRD analysis revealed that in the crystal structure of HDAMo, novel infinite [Mo₃O₁₀]²⁻ chains parallel to a axis are made up of distorted MoO₆ octahedra connected by corners and edges. The protonated HDA cations occupy channels formed by [Mo₃O₁₀]²⁻ chains and exhibit strong hydrogen bond interactions to terminal and bridging oxo groups of the chains. The [Mo₃O₁₀]²⁻ chains linked through protonated HAD cations formed a one-dimensional network. The HDAMo compound shows novel photochromic properties, i.e., its color changes from white to reddish brown gradually under UV irradiation. XRD, FT-IR, ESR spectra and XPS are used to investigate the photochromic behavior of the compound.     

Synthesis of Zwitter-Ionic Conjugate of Nido-Carborane with Cholesterol

9-HC≡CCH₂Me₂N-nido-7,8-C₂B₉H₁₁, a previously described carboranyl terminal alkyne, was used for the copper(I)-catalyzed azide-alkyne cycloaddition with azido-3β-cholesterol to form a novel zwitter-ionic conjugate of nido-carborane with cholesterol, bearing a 1,2,3-triazol fragment. The conjugate of nido-carborane with cholesterol, containing a charge-compensated group in the linker, can be used as a precursor for the preparation of liposomes for BNCT (Boron Neutron Capture Therapy). The solid-state molecular structure of a nido-carborane derivative with the 9-Me₂N(CH₂)₂Me₂N-nido-7,8-C₂B₉H₁₁ terminal dimethylamino group was determined by single-crystal X-ray diffraction.     

Iodocyclisation and rearrangement reactions of mono-protected allyl substituted guanidines

The iodocyclisation of a range N-allyl and N-homoallylguanidines using I₂/K₂CO₃ has been found to lead to a series of novel heterocycles which undergo selective rearrangements on variation of the reaction conditions, and predictable protecting group migration in the presence of trifluoroacetic acid in methanol.     

New Yorkite: A 4,8-connected tetragonal structural pattern in the space group <Emphasis Type="Italic">P</Emphasis>4/<Emphasis Type="Italic">mmm</Emphasis>

A novel hypothetical 4,8-connected tetragonal crystalline structure with a ternary stoichiometry AB₂C₂ is described. The novel pattern belongs to the space group P4/mmm (no. 123). The structure includes novel 8-connected anticube-centered vertices along with ordinary 8-connected cube-centered and 4-connected square-planar vertices. The structure may be representative of a ternary bimetallic fluoride, such as MRe₂F₂ or MTa₂F₂, where M is an alkaline-earth metal. The novel structure is unusual due to the absence of strains.     

Reaction of alkenes and dienes with t-butylmagnesium halides and zirconocene dihalides. A convenient procedure for hydrozirconation and a novel t-butylzirconation of conjugated alkenes

The reaction of nonconjugated monosubstituted alkenes with t-BuMgCl and Cl₂ZrCp₂ at room temperature produces the corresponding monoalkylzirconium derivatives in high yields, while conjugated alkenes undergo either a novel t-butylzirconation or hydrozirconation depending on the reaction conditions.     

Synthesis of novel 3-bromo-1,2-dihydroquinolines via palladium mediated intramolecular cyclization of N-tosyl-N-propargyl anilines

Facile synthesis of novel 3-bromo-1,2-dihydroquinolines by the intramolecular cyclization of N-tosyl-N-propargyl anilines catalyzed by Pd(OAc)₂ in conjunction with CuBr₂ and LiBr.     

A novel hydride-mediated reductive rearrangement of amide: a facile synthesis of pyrimidyl and triazinyl amines

LiAlH₄ and NaBH₄ were found to mediate the conversion of 2-(pyrimidyl-2-ylsulfanyl)-N-arylbenzamides and 2-(triazinyl-2-ylsulfanyl)-N-arylbenzamides into pyrimidyl and triazinyl amines under notably mild conditions via a novel reductive rearrangement mechanism. These reactions invent a new route to prepare amines, which are a kind of important biologically active compounds and provide the first insight into a novel hydride-promoted reductive rearrangement of amides.     

DAB-Cy as an inexpensive and effective ligand for palladium-catalyzed homocoupling reaction of aryl halides

A novel catalytic system of PdCl₂(CH₃CN)₂ with N,N′-dicyclohexyl-1,4-diazabutadiene (DAB-Cy) ligand was successfully used in reductive coupling of aryl halides.     

Hydrido Cyanoalkyls of platinum (II)

The preparation and reactions are described of some novel platinum(II) complexes with a hydride ligand group trans to an sp³ carbon, viz. [PtH(YCN)-(PPh₃)₂] with Y  (CH₂)_n (n = 1—3) or o-CH₂C₆H₄.     

Synthesis and reactivity of subvalent compounds. Part 13: Reaction of triethyl orthoformate with amines and selenium—a convenient one-step three-component synthesis for selenoureas

Selenoureas are obtained by a novel three-component condensation reaction from metallic selenium, triethyl orthoformate and a primary or secondary amine. The reaction is carried out as solvent-free one pot-procedure at 180-190°C under inert gas with a reaction time of 8 h. The reaction was tested for piperidine, isopropylamine, N,N′-dimethylpropylenediamine (Me-NH-CH₂-CH₂-CH₂-NH-Me) and N,N′-disubstituted ethylenediamines (R-NH-CH₂-CH₂-NH-R, R=Me, Et, ⁱPr, ^tBu, Ph).     

Highly active double metal cyanide complexes： Effect of central metal and ligand on reaction of epoxide/CO2

Various novel double metal cyanide (DMC) catalysts were successfully prepared by modifying the central metal (M) and one of cyanide ion (CN-) in Zna[M(CN)b]c complex. Such modifications have significant impact on the catalytic efficiency as well as the polymer selectivity for the reaction of PO/CO2. Zn–Ni(Ⅱ) DMC is a potential catalyst for alternating copolymerization of PO/CO2, and DMC catalysts based on Zn3[Co(CN)5X]2 (X = Br-and N3-) exhibit moderate efficiency for the production of polycarbonates. This research presents the preliminary exploration of novel DMC complex via chemical modification of its central metal and ligand.     

Chemical Derivatization and Characterization of Novel Antitrypanosomals for African Trypanosomiasis

The search for novel antitrypanosomals and the investigation into their mode of action remain crucial due to the toxicity and resistance of commercially available antitrypanosomal drugs. In this study, two novel antitrypanosomals, tortodofuordioxamide (compound 2) and tortodofuorpyramide (compound 3), were chemically derived from the natural N-alkylamide tortozanthoxylamide (compound 1) through structural modification. The chemical structures of these compounds were confirmed through spectrometric and spectroscopic analysis, and their in vitro efficacy and possible mechanisms of action were, subsequently, investigated in Trypanosoma brucei (T. brucei), one of the causative species of African trypanosomiasis (AT). The novel compounds 2 and 3 displayed significant antitrypanosomal potencies in terms of half-maximal effective concentrations (EC₅₀) and selectivity indices (SI) (compound 1, EC₅₀ = 7.3 μM, SI = 29.5; compound 2, EC₅₀ = 3.2 μM, SI = 91.3; compound 3, EC₅₀ = 4.5 μM, SI = 69.9). Microscopic analysis indicated that at the EC₅₀ values, the compounds resulted in the coiling and clumping of parasite subpopulations without significantly affecting the normal ratio of nuclei to kinetoplasts. In contrast to the animal antitrypanosomal drug diminazene, compounds 1, 2 and 3 exhibited antioxidant absorbance properties comparable to the standard antioxidant Trolox (Trolox, 0.11 A; diminazene, 0.50 A; compound 1, 0.10 A; compound 2, 0.09 A; compound 3, 0.11 A). The analysis of growth kinetics suggested that the compounds exhibited a relatively gradual but consistent growth inhibition of T. brucei at different concentrations. The results suggest that further pharmacological optimization of compounds 2 and 3 may facilitate their development into novel AT chemotherapy.     

Ab initio study of MgH2: Destabilizing effects of selective substitutions by transition metals

The strong ionicity of H within rutile MgH₂ is reduced by selective substitution of Mg by T (=Fe, Co, Ni, Pd, Pt) using trirutile super-structure host TMg₂H₆. These novel model systems, as computed in the quantum mechanical framework of density functional theory, showed a gradual decrease of the charges carried by H down to −0.02e improving the use of MgH₂ for applications.