Volume 60, Issue 9

Single crystals of the ternary copper(I) lanthanide(III) sulfides with the composition CuMS 2 (M = La - Nd, Sm, Gd, Tb) form within seven days at 800 °C by oxidation of elemental copper and lanthanide metal with sulfur (molar ratio: 1 : 1 : 2) in evacuated silica tubes when equimolar quantitites of CsCl are present as flux. The crystal structures (monoclinic, P2 1 /c, Z = 4; e. g. CuLaS 2 : a = 662.04(6), b = 730.89(6), c = 692.73(6) pm, β = 98.741(7)° and CuTbS 2 : a = 639.13(6), b = 700.02(6), c = 670.46(6) pm, β = 98.214(7)°) exhibit corrugated layers 2 ∞ {[Cu(S1) 3/3 (S2) 1/1 ] 3− } parallel to (100) which consist of vertex-linked pairs of [CuS 4 ] 7− tetrahedra sharing a common edge ([Cu 2 S 6 ] 10− ). Their three-dimensional cross-linkage is achieved by M 3+ cations in monocapped trigonal prismatic coordination of seven S 2− anions. The metal sulfur distances in the [CuS 4 ] 7− units cover with 230 - 233 (Cu-S2) and 231 - 238 (Cu-S1) as well as 241 - 248 (Cu-S1’) and 245 - 251 pm (Cu-S1”) a rather broad range, whereas those within the [MS 7 ] 11− polyhedra lie relatively closer together (M-S: 276 - 307 pm). The present work is the first comprehensive account of the knowledge acquired from X-ray single-crystal diffraction data for the whole isotypic series CuMS 2 (M = La - Nd, Sm, Gd, Tb).

1,3-Dimethylbarbituric acid (1, R = Me) reacts with aqueous formaldehyde in the presence of pyridine to give 1,3-dimethyl-2,4,6-trioxo-5-pyridinomethyl-1,3-perhydrodiazin-5-ylpyridinium ylide (6) in good yield. From 6 and 2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol- 2-ylidene (7), the zwitterionic imidazolium derivative 1,3-dimethyl-2,4,6-trioxo-5-(1,3-diisopropyl- 4,5-dimethylimidazoliomethyl)-1,3-perhydrodiazin-5-yl-imidazolium ylide (8) is obtained. Similarly, the phosphonium compound 1,3-dimethyl-2,4,6-trioxo-5-triphenylphosphoniomethyl-1,3- perhydrodiazin-5-y l-phosphonium ylide (9) is obtained from 6 and PPh 3 . The crystal structures of 8 and 9 are reported.

New compounds Ln 5 (Ag, Ga) 19−x (Ln = Gd, Tb) have been found to crystallise with the Rb 5 Hg 19 structure type (space group I4/m). The crystal structures were refined for Gd 5 Ag 1.8 Ga 15 and Tb 5 Ag 2 Ga 15.6 from X-ray powder data: a = 9.4635(1), c = 9.8638(2) Å , R I = 0.093 and a = 9.4313(1), c = 9.8491(2) Å , R I = 0.085, respectively. Some positions in the crystal structures of new the compounds are occupied partially.

The lithium rhodium stannide LiRh 3 Sn 5 was synthesized from the elements in a sealed tantalum tube and investigated via X-ray powder and single crystal diffraction: Pbcm, a = 538.9(1), b = 976.6(3), c = 1278.5(3) pm, wR2 = 0.0383, 1454 F 2 values, and 44 variables. Refinement of the occupancy parameters revealed a lithium content of 92(6)%. LiRh 3 Sn 5 crystallizes with a new structure type. The structure is built up from a complex three-dimensional [Rh 3 Sn 5 ] network, in which the lithium atoms fill channels in the b direction. The [Rh 3 Sn 5 ] network is governed by Rh-Rh (274 - 295 pm), Rh-Sn (262 - 287 pm), and Sn-Sn (289 - 376 pm) interactions. The lithium atoms have CN 13 (4 Rh+9 Sn). Electronic band structure calculations and the COHP bond analysis reveal strong Rh−Sn bonds and also significant Rh−Rh bonding within the Rh 3 Sn 5 network, which is additionally stabilized by weak but frequent Sn−Sn interactions.

A new dinuclear iron(III) derivative Fe 2 L(OCH 3 )Cl 2 (L = 1,3-bis[N-(5-chloro-2-hydroxybenzylidene)- 2-aminoethyl]-2-(5-chloro-2-hydroxyphenyl)imidazolidine) has been synthesized, it crystal structure determined and magnetically characterized. The two iron(III) ions are asymmetrically bridged by a phenoxo and a methoxo group and separated by 3.150(2)Å . The magnetic susceptibility of the complex was measured over the range 5 - 349.3 K and the observed data were successfully simulated by the equation based on the spin-Hamiltonian operator , indicating very weak antiferromagnetic coupling between the iron ions with J = −11.3 cm −1 . The magnetic and structural parameters of the compound and the nature of the magnetic super-exchange interaction are discussed and compared with data of similar dinuclear iron(III) complexes.

The synthesis of N-[4-(2-hydroxyethyl)-1,2,4-oxathiazinan-3-ylidene]-benzamide (2a) and N-[4- (2-hydroxyethyl)-1,2,4-oxathiazinan-3-ylidene]-2-fluorobenzamide (2b) by oxidation of the corresponding 1,1-bis(2-hydroxyethyl)-3-aroylthioureas with potassium iodate in aqueous solution is reported. Variable temperature 1 H NMR spectra of 2a prove that the heterocyclic 1,2,4-(O, S,N) sixmembered ring is involved in a dynamic chair-boat conformational interconversion. Molecular mechanic calculations show that the chair conformation is more stable than the boat conformation by 3.0 kcal/mol. The synthesis of the adduct [(2a)·0.5 HgCl 2 ] 3 as well as the X-ray structural characterization of 2a and 3 are also reported.

New zinc(II) and cadmium(II) complexes of the 2,2’-diamino-4,4’-bithiazole (DABTZ) ligand, [M(DABTZ) 2 (CH 3 COO)](ClO 4 ), have been synthesized and characterized by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. The structural characterization of the Cd(DABTZ) 2 (CH 3 COO)](ClO 4 ) · 2H 2 O complex shows the complex to be a monomer and the Cd atom to be coordinated by four nitrogen atoms of the “DABTZ” ligands and two oxygen atoms of the acetate anion. There is an edge-to-edge π-π stacking interaction between the parallel aromatic rings.

Five-, six- and seven-vertex dicarbaboranes, carborane anions and borane dianions have been studied by DFT calculations at the B3LYP/6-311+G(d,p) level of theory, aiming at determining the indirect nuclear spin-spin coupling constants with an emphasis on J( 11 B, 11 B), J( 13 C, 11 B) and J( 13 C, 13 C). The reasonable agreement with all experimental data suggests that the calculated data can be used in the discussion of the bonding situation in these cluster compounds, for which many coupling constants cannot be determined experimentally. The delocalisation of electron density is reflected by changes in both magnitude and sign of the coupling constants. The trend in the coupling constants between nuclei in antipodal positions points towards direct bonding interactions.

A simple and efficient protocol is described for the regioselective hydrolysis of terminal isopropylidene ketal protection in carbohydrate derivatives 1a - 11a. It uses either CoCl 2 · 2H 2 O in acetonitrile or InCl 3 in methanol at temperatures ranging from 50 to 60 °C. The low cost of CoCl 2 ·2H 2 O along with its requirement in catalytic quantities offers a great advantage for the multi-gram scale reaction.

1,2,5-Oxadiazinan-3,6-diones (8), easily available by cyclic carbonylation of α-amino-carbohydroxamic acids 7 with 1,1’-carbonyldiimidazole, are reacted with hydrazine to give 3- aminohydantoins (10). Depending on the substituents R 1 /R’ 8 was found to undergo an imidazole catalyzed oxidoreduction to 4-imidazolidinones (11) or α-iminophenylacetamides (12).

Three new isoflavonoids, griffonianone F, G and H were isolated from the seeds of Millettia griffoniana, along with the known prebarbigerone, pseudobaptigenin, pseudobaptigenin methyl ether, tephrosin, dipterixine, odorantine, 7,4’,5’-tetramethoxyisoflavone and isojamaicin. Their structures were assigned on the basis of spectroscopic data and chemical transformations.

Two new saccharinato-silver(I) (sac) complexes, [Ag(sac)(ampy)] (1), and [Ag 2 (sac) 2 (μ-aepy) 2 ] (2), [ampy = 2-(aminomethyl)pyridine, aepy = 2-(2-aminoethyl)pyridine], have been prepared and characterized by elemental analysis, IR spectroscopy, thermal analysis and single crystal X-ray diffraction. Complexes 1 and 2 crystallize in the monoclinic space group P 2 1/c and triclinic space group P1̄, respectively. The silver(I) ions in both complexes 1 and 2 exhibit a distorted T-shaped AgN 3 coordination geometry. 1 consists of individual molecules connected into chains by N-H···O hydrogen bonds. There are two crystallographically distinct dimers in the unit cell of 2 and in each dimer, the aepy ligands act as a bridge between two silver(I) centers, resulting in short argentophilic contacts [Ag1···Ag1 = 3.0199(4) Å and Ag2···Ag2 = 2.9894(4) Å ]. Symmetry equivalent dimers of 2 are connected by N-H···O hydrogen bonds into chains, which are further linked by aromatic π(py)···π(py) stacking interactions into sheets.

Decaline analogues of the bioactive fungal sesquiterpene (+)-isovelleral (1a), retaining the bicyclo[4,1,0]hept-2-en-1,2-dicarbaldehyde system, were prepared, and their cytotoxic and antimicrobial activities were compared with those of the natural product. While the two isomers (±)-2 and (±)-3 were as active as isovelleral (1a), the isomer (±)-4 was approximately 10 times less potent.

A series of 2,6-disubstituted pyridine derivatives were prepared from 2,6-diacetylpyridine or 2,6- dicarbonyl pyridine dichloride as starting materials. Reaction of 2,6-diacetylpyridine 1 with hydroxylamine hydrochloride or different aromatic aldehydes afforded the corresponding 2,6-diacetylpyridine dioxime and 2,6-bis-[β -(2-thienyl)acryloyl]pyridine derivatives 2 and 3, respectively. Additionally, N 2 ,N 2‘ -(pyridine-2,6-dicarbonyl)-L-amino acid hydrazides 5 were prepared starting from 2,6- dicarbonyl pyridine dichloride via the corresponding esters 4. Compound 3 was reacted with hydroxylamine hydrochloride to afford the 2,6-bis-[β -(2-thienyl)acryloyl-oxime]-pyridine derivative 6. Treatment of compounds 2 or 6 with phenyl isocyanate or phenyl isothiocyanate in refluxing dioxane gave the corresponding semicarbazide or thiosemicarbazide derivatives 7 and 8, respectively. Their treatment with toluene-3,5-diisocyanate afforded the macrocyclic semicarbzides 9 and 10, respectively. The chiral thiosemicarbazides 11a,b were however, prepared by treating compounds 5a,b with phenyl isothiocyanate followed by cyclization with sodium hydroxide (2N) yielding the triazoles 12a,b. Finally, the hydrazides 5a,b were treated with toluene-3,5-diisocyanate to afford the chiral macrocyclic tetrapeptide semicarbazides 13a,b in reasonable yields, while the expected cyclic dipeptide 14 was not formed. The structure assignments of the new compounds were based on chemical and spectroscopic evidence. The pharmacological screening showed that many of these compounds have good analgesic and anticonvulsant activities comparable to Voltarine ® and Carbamazapine ® used as reference drugs.

Reaction of 3-amino-2-hydroxypyridine and 2-amino(thio)phenols with various selected π-acceptors are herein reported. Different modes of cyclization via elimination and/or condensation reactions were observed during the reaction of the donors with 3,4,5,6-tetrachloro-1,2-benzoquinone (CHLo), 2,3,5,6-tetrachloro-1,4-benzoquinone (CHL-p), 2,3-dicyano-1,4-naphthoquinone (DCNQ) and 2- dicyanomethyleneindane-1,3-dione (CNIND). A series of pyridoxazines, benzoxa(thia)azines, benzoxa( thia)azepines has been synthesized in good yields.

Phytochemical studies on the petroleum ether extract of the roots of Eupatorium odoratum have resulted in the isolation of a novel triterpene, 3β -hydroxy-28-carboxyolean-12-ene (1) along with seven known compounds - poriferasterol (2), octadecane (3), butyrospermol acetate (4), bis(2- ethylhexyl)phthalate (5), chrysophanol (6), physcion (7) and palmitic acid (8). Novel compound 1 is designated as eupatoric acid. Compounds 2 - 7 were reported here for the first time from this plant. Palmitic acid (8) was also isolated for the first time from this root. The structure of the novel compound was established on the basis of spectroscopic studies. The cytotoxicity of the compounds 1 - 7 was studied using a lethality test against Artemia salina (brine shrimp).

A sesquiterpene-lactone of the guaianolide class (nubenone) and a seco-guaianolide (nubenoic acid) have been isolated from Salvia nubicola collected in Quetta, Pakistan. Structures of both sesquiterpenes were elucidated with the aid of spectroscopic techniques including two dimensional NMR spectroscopy.

The reaction of tetrapyrrolidinodiborane(4) (1) with BBr 3 in a 1:1 molar ratio yields a mixture of 1,2-dibromo-1,2- dipyrrolidinodiborane(4) (2) and bromotripyrrolidino- diborane( 4) (3), while a 1:2 molar ratio leads in Et 2 O to compound 2 as the main product along with a small amount of [(C 4 H 8 N) 2 B 2 Br 3 (OEt)] (4). The new compounds have been characterized by NMR and MS data, as well as by X-ray structure analyses of 2 and 4, of which the former exhibits an interesting polymorphism phenomenon.