Volume 66, Issue 12

This review describes the multi-component reactions of barbituric acid derivatives as building blocks for the synthesis of heterocyclic compounds with pharmacological interest Graphical Abstract Barbituric Acid Utility in Multi-Component Reactions

Hydrazinolysis of carboxylic acid esters in alcoholic solutions is the standard method for preparing carbohydrazides (carboxylic hydrazides). Here we report an efficient process, involving the reaction of activated esters or amides with hydrazine, for the preparation of thiophenecarbohydrazides in yields larger than 90% and high purity. With this new method, a series of heteroaryl-, aryl-, or aralkyl- substituted carbohydrazides were synthesized and characterized. The X-ray crystal structure of 2-thiophenecarbohydrazide (thiophene-2-carboxylic hydrazide, 2-thenoyl-hydrazine) has revealed that it crystallizes in the monoclinic system, space group P2 1 /c, with cell parameters of a = 6.1202(2), b = 8.3907(3), c = 12.5332(5) Å, β = 98.6577(11)°, Z = 4, R(F) = 0.0455 and wR(F 2 ) = 0.1805, T = 293 K. Graphical Abstract 2-Thiophenecarbohydrazides: A Novel Efficient Method for the Synthesis of 2-Thiophenecarbohydrazide

A Fischer indole synthesis with a cis-configurated octahydroisobenzofuran-6-one yielded exclusively a furo[3,4-c]carbazole derivative as the product of a regioselective angular annulation reaction. A Friedländer quinoline synthesis from the same substrate gave a mixture of angular and linear annulation products, i. e. furo[3,4-a]acridine and furo[3,4-b]acridine derivatives. When submitting a mixture of cis- and trans-octahydroisoindole derivatives to Fischer and Friedländer syntheses, the trans-starting material gave regioselectively linear annulation products, i. e. pyrrolo[3,4-b]carbazole and pyrrolo[3,4-b]acridine derivatives. In contrast, the respective cis-configurated isoindole gavemixtures of angular and linear annulation products. The constitutions and relative configurations of nine new indole and quinoline derivatives were established by 2D NMR experiments and X-ray singlecrystal investigations. Graphical Abstract Investigations into the Regioselectivity of Fischer Indole and Friedländer Quinoline Syntheses with Octahydroisobenzofuran and Octahydroisoindole Derivatives

The intermetallic compounds M 5 T 2 Cd (M = Ca, Yb, Eu; T = Cu, Ag, Au) and Yb 5 Cu 2 Zn were synthesized by melting the elements in sealed tantalum tubes followed by annealing at 923 K. All phases were characterized on the basis of powder and single-crystal X-ray diffraction data: Mo 5 B 2 Si type, I4/mcm, Z = 4, a = 828.7(1), c = 1528.1(3) pm, wR2 = 0.030, 440 F 2 values, 16 variables for Eu 5 Cu 2 Cd, a = 788.2(1), c = 1459.3(5) pm, wR2 = 0.053, 378 F 2 values, 16 variables for Yb 5 Cu 2 Cd, and a = 797.2(1), c = 1438.8(3) pm, wR2 = 0.036, 386 F 2 values, 17 variables for Yb 5 Au 2.19 Cd 0.81 , which shows a small degree of Au / Cd mixing. The M 5 T 2 Cd structures are intergrowth variants of slightly distorted CuAl 2- and U 3 Si 2- related slabs. Striking coordination motifs (exemplary for Eu 5 Cu 2 Cd) are square antiprisms of the Eu atoms around Cd, Eu 8 square prisms around Eu, and trigonal Eu 6 prisms around Cu within the AlB 2 -related slab. Temperature-dependent magnetic susceptibility measurements showed Pauli paramagnetism for Yb 5 Cu 2 Zn, indicating purely divalent ytterbium. Eu 5 Au 2 Cd exhibits Curie-Weiss behavior above 100 K with an experimental magnetic moment of 8.14 μ B per Eu atom and a Weiss constant of 56 K. Antiferromagnetic ordering of the EuII magnetic moments is evident at 36 K, and a metamagnetic transition is observed at 25 K and 13 kOe. Graphical Abstract Intermetallic Cadmium Compounds M 5 T 2 Cd (M = Ca, Yb, Eu; T = Cu, Ag, Au) with Mo 5 B 2 Si-type Structure

Dichloroboryldisilylamines [SiCl m (CH 3 ) 3−m ]N[Si(CH 3 ) 3 ](BCl2) (m = 1 - 3) as well as chloromethylboryl- bis-(chlorodimethylsilyl)amine [SiCl(CH 3 ) 2 ] 2 N[BCl(CH 3 )] form 1 : 1 adducts with pyridine (1 - 4). Those with m = 2 and 3 have been converted into functionalized diazadiboretidine derivatives which are still coordinated by pyridine: [(SiCl m (CH 3 ) 3−m )NBCl · Py] 2 (5: m = 2, 6: m = 3). Single-crystal X-ray diffraction structure analyses confirm the presence of planar, rhombusshaped, four-membered boron-nitrogen rings with tetra-coordinated boron atoms and nitrogenbonded, chlorine-functionalized silyl groups, for both compounds. Graphical Abstract Pyridine-promoted Cyclization of Functionalized N-Silylated Boron-Nitrogen Compounds

The 4-picolinium salt (C 6 H 8 N) 3 [PMo 12 O 40 ] was synthesized hydrothermally and characterized by IR spectroscopy, TG-DTA data and single-crystal X-ray diffraction. The results indicate that the compound consists of a [PMo 12 O 40 ] 3− heteropolyoxoanion and 4-picolinium cations [C 6 H 8 N] + . A supramolecular structure is formed via intermolecular hydrogen-bonding between the different structural units. Crystal data: monoclinic, space group P2 1 /c, a = 19.7004(3), b = 14.0785(2), c = 33.0209(5) Å, β = 91.3590(10)°, V = 9155.8(2) Å 3 , Z = 8, wR2 = 0.0730. (C 6 H 8 N) 3 [PMo 12 O 40 ] has a high catalytic activity for the oxidative elimination of acetone from gases as tested in a continuousflow fixed-bed micro-reactor. When the initial concentration is 5.2 gm −3 in air, and the flow rate is 3.3 mLmin −1 , 93% of the acetone is eliminated at 70 °C. Graphical Abstract Crystal Structure and Catalytic Properties of (C 6 H 8 N) 3 [PMo 12 O 40 ]

A novel two-dimensional complex based on the mono-vacant Keggin anion [PW 11 O 39 ] 7− , [Ni(BIIM) 3 ] 3 [{Ni(BIIM) 2 } 2 (PNiW 11 O 39 ) 2 (BIIM)]・H 2 O (BIIM = 2,2ʹ-biimidazole), was hydrothermally synthesized and characterized by elemental and thermo-gravimetric analysis, IR and UV spectroscopy. Each [PW 11 O 39 ] 7− anion captures an Ni 2+ ion forming a [PNiW 11 O 39 ] 5− polyanion, two of which are linked together by a BIIM ligand into a [(PNiW 11 O 39 ) 2 (BIIM)] 10− polyanion supporting two Ni(BIIM) 2 2+ units through two terminal oxygen atoms and affording a complicated [{Ni(BIIM) 2 } 2 (PNiW 11 O 39 ) 2 (BIIM)] 6− heteropolyanion. Each of these units is further attached to four surrounding equivalent units by their own Ni(BIIM) 2 2+ linkers into a two-dimensional brick wall-like network with (6,3) topology. Graphical Abstract A Rare Two-dimensional Network Based on 2,2ʹ-Biimidazole Bridged Double [PW 11 O 39 Ni] 5 – Polyanions

Powder samples and single crystals of the boride phases M x Rh 7−x B 3 (M = Cr,Mn, Ni; x ≤ 1) have been synthesized from the elements using an arc-melting furnace under purified argon atmosphere in a water-cooled copper crucible. The new phases were characterized from single-crystal and powder X-ray diffraction, as well as semi-quantitative EDX measurements. The obtained phases crystallize in the hexagonal Th 7 Fe 3 structure type (space group P6 3 mc, no. 186, Z = 2). In all cases (M = Cr, Mn, Ni), M is found to preferentially mix with rhodium at only one (6c) of the three available rhodium positions. Pauli paramagnetism was observed in Cr x Rh 7−x B 3 (x < 1), whereas both Pauli and temperature-dependent paramagnetisms were found in NiRh 6 B 3 . Graphical Abstract Synthesis, Crystal Chemistry and Magnetism of the Metal-rich Borides M x Rh 7–x B 3 (M = Cr, Mn, Ni; x = 0.39–1) with Th 7 Fe 3 -type Structure

Three new cesium oxometallates with trigonal-planar [MO 3 ] n− anions (M = Zn, Fe, B) were observed as products of reactions aimed at the formation of alkali metal suboxometallates A9MO4 (A = Rb, Cs; M = Al, Ga, In, Fe, Sc), or as decomposition products thereof. Cs 4 [FeO 3 ], Cs 4 [ZnO 3 ] and Cs 3 [BO 3 ] crystallize with new structure types (Cs 4 [FeO 3 ]: triclinic, space group P1̄ , a = 7.0652(1), b = 7.125(1), c = 9.939(2) Å, α = 80.74(2), β = 71.32(2), γ = 64.04(2)°, Z = 2, Cs 4 [FeO 3 ]: monoclinic, space group P2 1 /c, a = 7.146(4), b = 18.572(1), c = 7.050(4) Å, β = 115.47(4)◦, Z = 4, Cs 3 [BO 3 ]: orthorhombic, space group Pnma, a = 10.967(1), b = 10.967(1), c = 10.353(1) Å). In all structures the trigonal-planar anions have no or low point symmetry, but deviate only marginally from ideal 6̄m 2 symmetry. The new crystal structures can be derived from simple and highly symmetrical packings of spheres or from known binary structure types. Graphical Abstract The New Oxometallates Cs 4 [FeO 3 ], Cs 4 [ZnO 3 ] and Cs 3 [BO 3 ] with Trigonal-planar Anions – Decomposition Products of Alkali Metal Suboxometallates

1-(2,2ʹ-Diethoxyethyl)-3-methyl-imidazolium bromide, 1, has been prepared and used as a precursor for the synthesis of the corresponding silver bromide complex [(NHC) 2 Ag][AgBr 2 ], 2. Transmetallation of 2 with (tht)AuBr (tht = tetrahydrothiophene) yields (NHC)AuBr, 3. The solid-state structures of 2 and 3 have been determined by single-crystal X-ray diffraction revealing a loose aggregation of the complexes by weak metal-metal interactions. Due to the presence of these contacts, both complexes are emissive in the solid state. Graphical Abstract Synthesis, Characterization and Luminescence of Silver(I) and Gold(I) Complexes Bearing a Diethyl Acetal Functionalized N-Heterocyclic Carbene

Crystals of pyridinium tetrabromozincate and pyridinium tetrabromocadmate were obtained as monohydrates and anhydrous compounds. The crystal structure of metastable (C 5 H 5 NH) 2- CdBr 4 ・H 2 O was determined at 300(2) K; triclinic space group P1̄ with a = 7.875(2), b = 8.151(1), and c = 16.356(2) Å, α = 79.260(10), β = 86.030(10), and γ = 61.440(10)°, Z = 2. All compounds except for stable (C 5 H 5 NH) 2 CdBr 4 ・H 2 O gave four 81 Br NQR lines at temperatures between 77 and around 325 K. The stable (C 5 H 5 NH) 2 CdBr 4 ・H 2 O undergoes a first-order phase transition at T C = 116 K. Four 81 Br NQR lines below T C merged into two with equal intensities above T C , indicating a 180° flip motion of water molecules in the r. t. phase. The 81 Br NQR lines of the two anhydrous compounds faded out around 325 K probably due to the reorientational motion of ZnBr 4 2− or CdBr 4 2− ions. The respective two 81 Br NQR lines of the hydrates exhibited anomalous positive temperature dependence. This is considered to be induced by a weakening in the interionic C-H・ ・ ・Br hydrogen bonds with increasing temperature. The DSC measurements of the anhydrous compounds have revealed phase transitions above r. t. The thermal behavior of (C 5 H 5 NH) 2 CdBr 4 is complicated by the formation of metastable forms. Graphical Abstract NQR, DSC, and X-Ray Structure Studies of Pyridinium Tetrabromozincate and Pyridinium Tetrabromocadmate (C 5 H 5 NH) 2 MBr 4 · nH 2 O (M = Zn and Cd; n = 0, 1); Phase Transitions and Weak Hydrogen Bond Interactions

Phytochemical investigation of the roots of Salacia longipes var. camerunensis led to the isolation of a new triterpenoid, salacetal (1), together with the known compounds mangiferin, 2-hydroxy- 3-oxo-D:A-friedooleanan-29-oic acid, β -sitosterol, and stigmasterol. The structure of the new compound as well as those of the known compounds were established by means of spectroscopic methods and by comparison with reported data. Graphical Abstract Salacetal, an Oleanane-type Triterpene from Salacia longipes var. camerunensis

An innovative route for intramolecular cyclization of pent- 4-en-1-ol has been delineated through a ring closing reaction with phenylselenyl halides, in good yield. Several catalysts (triethylamine, quinoline, 2,2ʹ-bipyridine, pyridine, CoCl 2 and SnCl 2 ) enable fast, facile and efficient cyclization. Graphical Abstract Cyclization of Unsaturated Alcohols. Mild and Efficient Selenocyclization of Pent-4-en-1-ol