Volume 55, Issue 5

Treatment of bis[bis(trimethylsilyl)amino]germanium(II) with elemental sulfur or selenium affords high yields of the corresponding monosulfide [(Me 3 Si) 2 N] 2 GeS and selenide [(Me 3 Si) 2 N] 2 GeSe, respectively. The crystalline products have now been shown to be cyclic dimers with (GeS/Se) 2 four-membered rings by X-ray single crystal structure analysis. The crystal structure of (triphenylphosphine)gold(I) bis(trimethylsilyl)amide (Ph 3 P)Au-N(SiMe 3 ) 2 has also been determined. The molecule is a monomer with a tricoordinate nitrogen atom in a planar configuration [Si 2 NAu]. The compound does not undergo insertion of the bis[bis(trimethylsilyl)amino]germylene.

A series of aminosilanes (R′HN) 2 SiR 2 : have been prepared. In case of bulky substituents R′ the aminolysis of Ph 2 SiCl 2 stops at the (R′HN)ClSiPh 2 stage. Replacement of the Cl atom is achieved with LiNHR′ which allows the synthesis of mixed bisaminosilanes (R′HN)(R″HN)SiPh 2 . The X-ray structures of three of these compounds have been determined. There are no intermolecular N-H···N hydrogen bonds in these compounds in the solid state. Several 1,3,2,4-diazaphosphetidines have been synthesized using bis(N-lithioamino)silanes and bis(N-lithioamino)phosphanes . Amongst these the heterocycle 18 possesses an almost planar four membered N 2 SiP ring system.

The crystal and molecular structures of dithienyl ditelluride (C 4 H 3 S) 2 Te 2 (1), difuryl ditelluride (C 4 H 3 O) 2 Te 2 (2), dithienyl diselenide (C 4 H 3 S) 2 Se 2 (3), and difuryl diselenide (C 4 H 3 O) 2 Se 2 (4) are reported in this paper and compared to those of other simple diaryl ditellurides and diselenides. The chalcogen-chajcogen bonds exhibit approximately single bond lengths [Te-Te = 2.7337(8) and 2.7240(4) Å in 1 and 2, respectively; Se-Se = 2.357(1) and 2.368(2) Å in 3 and 4, respectively], as do the chalcogen-carbon bond lengths [Te-C = 2.095(9) - 2.104(6) in 1 and 2.091(6) - 2.105(9) Å in 2; Se-C = 1.87(1) - 1.90(1) Å in 3 and 1.887(8) - 1.897(10) Å in 4]. The aromatic rings are disordered. The dihedral angles C-E-E-C range from 79(2) to 96(1)° are consistent with the concept of minimized p lone-pair repulsion of adjacent chalcogen atoms. The dependence of molecular parameters on the angle between the aromatic rings and the chalcogen-chalcogen bonds follow trends established previously for aromatic disulfides. Though the bond parameters and conformations of 1 - 4 are similar, the packing of the molecules is different. The two ditellurides 1 and 2 show short Te···Te contacts (3.900 - 4.002 Å in 1 and 4.060 - 4.172 Å in 2). The two diselenides 3 and 4 do not exhibit close chalcogen-chalcogen interactions. The NMR spectroscopic properties of 1 - 4 are discussed.

2-Aryl-substituted propionic acids, such as the important anti-inflammatory agent Naproxen, exist in two enantiomeric forms. The (S)-enantiomer of 2-(6-methoxynaphth-2-yl)propionic acid 1 is about 28 times more effective than the (S)-enantiomer. A new catalytic method to synthesize Naproxen (S)-1 involves the enantioselective decarboxylation of suitably substituted malonic acid derivatives. Thus, 2-(6-methoxynaphth-2-yl)-2-methylmalonic acid 6 and its monoester 7 were stirred in THF with catalytic amounts of chiral bases, which induced decarboxylation. After work-up, optical inductions up to 39.8% ee were found in the resulting products 1 and 9. The optically active bases may be fully recycled by extraction.

The 1:1 complex of palladium(II) chloride with 2-(2-methyl-3-phenyl-isoxazolidin-5-yl)- pyridine (L) has been prepared and studied by means of elemental analysis, 1 H NMR spectroscopy and X-ray diffraction (monoclinic, space group P2 1 /n with parameters: a = 8.141(2), b = 9.750(2),c = 20.691(6)Å ,β = 95.62(3)°,V = 1634.4(7)Å 3 ,Z = 4 ;R1= 0.054 and wR2= 0.144 for 3352 unique reflections). A square-planar coordination polyhedron has been established for the palladium atom both in acetone solution and in the solid state. The organic ligand is coordinated toometal in a bidentate manner via nitrogen atoms of the pyridine substituent (Pd-N(2) 2.125(3) Å) and the isoxazolidine heterocycle (Pd-N(l) 2.102(3) Å). The other two coordination positions of palladium are occupied by chlorine atoms (Pd-Cl(l) 2.321(1) and Pd-Cl(2) 2.333(1) Å). The six-membered chelate ring formed by Pd, N(2), C(4), C(1), 0(1) and N (1) possesses a “twist-tub” conformation. The isoxazolidine cycle has an envelope conformation with an equatorial orientation of the methyl group.

[Ph 4 P] 2 [Pb 3 Br 8 ] and [Ph 4 As] 2 [Pb 3 Br 8 ] crystallize both in the monoclinic space group P 2 1 /n. The lattice parameters of [Ph 4 P] 2 [Pb 3 Br 8 ] are a = 14.637(7), b = 8.151(3), c = 23.388(8) Å, β = 106.02(3)°, Z = 2 and of [Ph 4 As] 2 [Pb 3 Br 8 ] are a = 14.697(7), b = 8.219(3), c = 23.527(8) Å, β = 106.27(3)°, Z = 2. The lattice parameters of [Ph 4 P][PbBrCl 2 ]·CH 3 CN, which crystallizes in the triclinic space group (P 1̅), are a = 9.435(3), b = 10.2577(14), c = 14.055(2) Å, α = 88.320(11)°, β = 84.82(2)°, γ = 84.19(2)°, Z = 2. 207 Pb NMR shifts of halogenoplumbates in solution are reported.

Ag 2 CN 2 precipitates on mixing aqueous solutions of H 2 CN 2 and silver nitrate as a yellow crystalline solid. The title compound was characterised by single crystal X-ray diffraction and IR-spectroscopy (monoclinic, P2 1 /c (No. 14), a = 7.315(1), b = 6.010(1), c = 6.684(1) Å; β = 102.29( 1)°; Z = 4). The anion is slightly bent (177.1 (5)°) and exhibits two significantly different bond lengths (C-N(l): 1.194(6), C-N(2): 1.266(5) Å).

1,3-Dimethyluracil (DMU) forms a complex with copper(I) iodide which shows a green luminescence at λ max = 505 nm. With PF 6 - counter ions a photoactive Cu(I)DMU complex is generated which shows a long-wavelength absorption at λ max = 335 nm. Light absorption by this band leads to a dimerization of DMU to its cyclobutane dimer.

Several new pyridines, pyridones and pyrans fused to benzothiepine or benzoheptene ring were synthesized as potential anticancer and anti-HIV agents. The fused-ring pyridines 6. 7 and 17-19 were obtained via the reaction of the seven-membered ring ketones 1, 2 and 3 with an arylidene-malononitrile and by treatment of the ylidenemalononitriles 14, 15 and 16 with aromatic aldehydes, respectively. The corresponding pyridones 11, 12 and 13 were prepared from the ketones 1, 2 and 3 and arylmethylenecyanoacetamide. The synthesis of the fused-ring pyranes 8 and 9 involved the condensation of the ketones 4 and 5 with malononitrile under basic conditions. The rearrangement of 8 under acidic conditions gave the tetrahydropyridine 10. The pyran 20 was obtained from 15 and benzaldehyde. The screening tests showed that many of the compounds obtained exhibit good anticancer activity comparable to 5-fluorodeoxyuridine used as reference compound and moderate anti-HIV activity in comparison with AZT.

The recently reported binary stannide Ti 2 Sn 3 is confirmed. Its structure was determined from single-crystal X-ray diffractometer data: Cmca, a = 596.7(4), b = 1995(2), c = 701.3(4) pm , Z = 8, R = 0.027 for 817 structure factors and 30 variable parameters. The crystal structure is compared to that of V 2 GaSn 2 , which has the same space group symmetry and atomic positions. The Ga atoms of V 2 GaSn 2 occupy those Sn positions of Ti 2 Sn 3 which have the smaller coordination number. The two different titanium atoms of Ti 2 Sn 3 have 11 neighbors of which 3 and 4, respectively, are titanium atoms. The three different tin atoms have 5 titanium with 8 or 10 additional tin neighbors. They show only a slightly broadened but unresolved 119 Sn Mössbauer signal with an isomer shift reflecting the high tin content of this intermetallic compound and a relatively large quadrupole splitting of 2.10 mm·s -1 . Ti 2 Sn 3 is a good metallic conductor and a Pauli paramagnet.

A new, mild, efficient and environm entally benign method for the cleavage of oximes has been achieved by a simple reaction f oximes with wet alumina supported chromium (VI) oxide under microwave irradiations in solvent-free condition.

1-Methylpyridinium salts showed no reaction with excessive hydroxylamine, but nicotinic acid derivatives in HMPT gave the corresponding N-oxides. 3-Acetyl-1-methylpyridinium iodide generated the hydroximino-pyridine 1-oxide 13 and the isoxazoles 14, 15E, and 15Z. 2- and 4-Cyano-l-methylpyridinium iodides underwent no ring cleavage, but altered only the functional group. However, the 3-cyano compound was converted into the corresponding pyridine N-oxides with carboxamide, hydroxyamidine and carbaldoxime groups.

The reaction of 6-aminouracil 1 with formaldehyde and secondary amines in ethanol at room temperature gave the corresponding 5-alkylaminomethyl derivatives (2a-c) and bis(4- pyrimidyl) methane (4). Also, Mannich reaction with primary aliphatic and aromatic amines at room temperature afforded pyrimid[4,5-d]pyrimidine (5 and 6). Treatment of 1 with o-phenylenediamine through transamination gave com pound 7 which cyclized through intramolecular Mannich reaction with formalin to yield pyrimido[4,5-e]-[l,4]diazepine (8).

The title compound has been prepared from cobalt( II) acetate and Me 3 SiNPEt 3 in boiling toluene in the presence of silicon grease and traces of water as blue single crystals which were characterized by IR spectroscopy and by a crystal structure determination. Space group Pbca, Z = 8, lattice dimensions at -50 °C: a = 1449.3(1), b = 1724.9(1), c = 2356.6(2) pm, R = 0.0548. [Co 4 (ν 3 -NPEt 3 ) 2 (HNPEt 3 ) 2 (O 2 C-CH 3 ) 2 -(v-OSiMe 2 OSiMe 2 O) 2 ] has a centrosymmetric structure. The four cobalt atoms which are coordinated tetrahedrally are v 3 -bridged via the N atoms of the two (NPEt 3 - ) groups and v 2 -bridged by the O atoms of the chelating (OSiMe 2 OSi-Me 2 O 2- ) units. The core atoms are arranged in three four-membered rings which are connected in a stair-like way.