Volume 58, Issue 9

Chiral binaphthyl compounds, especially those with different substituents in 2- and 2’-position of the binaphthyl system, have gained interest as constituents of successful ligands in various catalytic reactions. Here, we present the synthesis and characterization of new binaphthyl ligands containing oxazoline, cyano and amide substituents in 2’-position in addition to methoxy, hydroxy or amino groups in 2-position. Starting from these compounds new ligands for enantioselective catalysis will be accessible.

The title compounds have been synthesized by reacting the elements in sealed niobium or tantalum tubes in a high-frequency furnace. They crystallize with the hexagonal ZrNiAl type structure, space group P62m. All gallides have been characterized through their X-ray powder diffractogram. The cell volume decreases from the lanthanum to the lutetium compound as expected from the lanthanoid contraction. The structures of LaMgGa, PrMgGa, NdMgGa, SmMgGa and TmMgGa have been refined from single crystal diffractometer data. The structures contain two crystallographically independent gallium sites which both have a trigonal prismatic coordination: Ga1 by six RE and Ga2 by six Mg atoms. These trigonal prisms are capped on the rectangular sites by three Mg (RE) atoms, leading to coordination number 9 for each gallium atom. Together, the gallium and magnesium atoms form a three-dimensional [MgGa] network in which the rare earth atoms fill distorted hexagonal channels. Within the network the magnesium atoms have short Mg-Mg contacts, i. e. 312 pm in SmMgGa. The Mg-Ga distances in that gallide range from 284 to 287 pm. Bonding in the network is thus governed by strong Mg-Ga and Mg-Mg bonding. EuMgGa crystallizes with the orthorhombic TiNiSi type: Pnma, a = 783.1(2), b = 472.8(1), c = 829.8(2) pm.

SmCl 3 reacts with equimolar amounts of K[(S)-C 5 H 4 CHPhCH 2 NMe 2 ] and Na[C 5 Me 5 ] yielding [(S)-C 5 H 4 CHPhCH 2 NMe 2 ](C 5 Me 5 )SmCl(1). The methylation of complex 1 with LiMe and the reactions of the known analogues of 1, [(S)-C 5 H 4 CHPhCH 2 NMe 2 ](C 5 Me 5 )LnCl (Ln = Y (2), Lu (3)) with LiCH 2 SiMe 3 afford [(S)-C 5 H 4 CHPhCH 2 NMe 2 ](C 5 Me 5 )SmMe (4) and [(S)-C 5 H 4 CHPhCH 2 NMe 2 ](C 5 Me 5 )LnCH 2 SiMe 3 (Ln = Y (5), Lu (6)), respectively. The reactions of ScCl 3 and LuCl 3 with 1 equivalent of K[(S)-C 5 H 4 CHPhCH 2 NMe 2 ] or K[C 5 H 4 CH 2 CH 2 NMe 2 ] followed by 2 equivalents of Me 3 SiCH 2 Li yield the complexes [(S)-C 5 H 4 CHPhCH 2 NMe 2 ] Ln(CH 2 SiMe 3 ) 2 (Ln = Sc (7a), Lu (7b)) or (C 5 H 4 CH 2 CH 2 NMe 2 )Ln(CH 2 SiMe 3 ) 2 (Ln = Sc (8a), Lu (8b)), respectively.

Treatment of the ligand system (ο-C 6 H 4 OH)-S-CH 2 -CH 2 -S-(ο-C 6 H 4 -OH) (2a) with TiCl 4 gave the metalla-crown ether derivative [(-S-CH 2 -CH 2 -S-)(ο-C 6 H 4 O) 2 ]TiCl 2 (5a). Complex 5a was characterized by an X-ray crystal structure analysis. It showed a pseudo-octahedral structure with both sulfur atoms being cis-coordinated to the metal center. The chloride ligands are also cispositioned, whereas the remaining two Ti−oxygen bonds are trans to each other to complete the distorted octahedral coordination geometry. The reaction of 2a with ZrCl 4 gave the analogous complex 5c. The related ligand system (ο-C 6 H 4 OH)-O-CH 2 -CH 2 -O-(ο-C 6 H 4 OH) (2b) was doubly deprotonated by treatment with butyl lithium and then reacted with TiCl 4 to yield the complex [(-O-CH 2 -CH 2 -O-)(ο-C 6 H 4 O) 2 ]TiCl 2 (5b).

A novel class of cyclopropanoic nucleoside analogues containing an hydroxyethyl residue instead of a hydroxymethyl side chain has been prepared in an easy sequence. These compounds showed weak antitumor activity. The resolution of the racemates on an analytical scale was performed by HPLC using chiral stationary phases.

A novel class of difluorinated cyclopropanoic nucleoside analogues containing a propyl spacer between the cyclopropane ring and the heterocycle has been prepared. Some of these compounds showed weak antitumor activity in prelimary screenings. The resolution of these racemic compounds on an analytical scale was performed by HPLC using chiral stationary phases.

A series of chiral macrocyclic pyridines has been prepared starting from N 2 ,N 2 -(pyridine- 2,6-dicarbonyl)diamino acid hydrazides (2a-c) and N,N-bis-(1-carboxy-2-substituted)-2,6- diaminocarbonyl)pyridines (3a,b). The coupling of (2a-c) with 2,6-pyridine dicarbonyldichloride (4) gave the compounds (5a-c). Compounds 2a-c were coupled with 2,6-diacetylpyridine (6) to yield compounds (7a-c) and with heterocyclic aldehydes (8) or (10) to give the compounds (9a-c) or (11a-c). In addition, the hydrazides (2a-c) were reacted with diformylcalix[4]arene 12 to afford the macrocyclic calix[4]arene hydrazone derivatives (13a-c) in reasonable yields. Finally, reaction of diaminocalix-[4]arene derivatives (14a,b) with hydrazides 2a,b or acids (3a,b), using azide or mixed anhydride methods afforded macrocyclic calix[4]arene derivatives 15a,b and 16a,b, respectively. The structure assignments of the new compounds are based on chemical and spectroscopic evidence. The biological activity screening tests showed that many of the obtained compounds exhibit high antimicrobial activity comparable to ampicillin and chloramphenicol which are used as reference compounds.

Stacking of an arene D on caffeine (1) near 7-Me and 8-H is known ( 1 H NMR shifts, CCl 4 , AUS concept) to yield the same association constant K for each signal of 1. Toluene (T) and 1 now yielded the same K from 7-Me and 8-H while K from 1-Me (and 3-Me) is smaller indicating a minor stacking centre near N-1 that forms both 1T and 1T2; this 1T2 disturbs computations of K. The main stacking centre forms no 1T2 since its 1T is stabilized by dipole-dipole interaction. Diphenylmethane Dp, a substituted T that cannot form a dimer of type T2, does not form 1Dp2. Ethyl of 1-ethyltheobromine (2) is proven to stand perpendicular so that the above minor complex can only arise on one face of 2 halving K minor and making the disturbance of computations by 2T2 insignificant; apart from this minor 2T there are cis-trans isomers of the main complex. Stacking of 1 and 2 with larger arenes is discussed in terms of relative molecular sizes under consideration of the perpendicularly placed ethyl group of 2. Stacking of D near N-3 and N-9 of 1,3,7,9-tetramethyluric acid (4) is known. 4 and T now provided K = 0.218 l mol −1 from 3-Me and 9-Me but K = 0.157 l mol −1 from 1-Me and 7-Me. This and the complex induced shifts IK indicate formation of stacking 4T + 4T2 and of two edge-on 4T standing on 3-Me and 9-Me under dipole-dipole interaction with a neighbouring oxygen. The oxygens of 4 (and probably of 1, too) form edge-on complexes with hexafluorobenzene; this underlines the importance of polar effects.

Four novel stable enols (one characterized by X-ray crystal structure analysis) were synthesized and investigated under oxidative conditions to yield benzofurans. Depending on the donor qualities of the heteroaryl substituent the reaction following the one-electron oxidation could be stopped on the stage of the cyclohexadienyl cation whose lifetime was measured. Oxidation potentials were determined for the enols, the enolates and the α-carbonyl radicals. Oxidation of benzofurans yielded dimeric species or intramolecular cyclization products.

The aminomethylation of the α-carbonylhydrazones 1 and 14 with N,N,N′,N′-tetralkylaminals yields only N,N- or C,N-bis-aminomethyl products, but no C-mono-aminomethyl compounds. Phenylglyoxal N-methylhydrazone (24) yields the Mannich bases 27, while anilinocarbonyl hydrazone 29 dependent on the conditions gives rise to the N-aminomethyl derivatives 30 or to the Mannich bases 31. From benzoylhydrazone 33 and semicarbazone 35 the Mannich bases 34 and 36, respectively, are available. Mercury-EDTA reacts with 27 and 31 by twofold dehydrogenation and cyclization to form the lactams 46 and 47, respectively, whose treatment with perchloric acid yields the triazinium salts 45 and 51. When Mannich base 34 is exposed to the same oxidation conditions, the products of both dehydrogenation steps, 54 and 55, may be isolated. From the semicarbazones 36 only the triazines 56 are produced after a single dehydrogenation step.

In continuation to our search for new amino acid and peptide based anti-inflammatory agents, the suggestion, synthesis, structure elucidation of some N α -bis-dipicolinoyl amino acids, linear tetra and cyclic octa bridged peptides 1-9, of which four are new compounds 6-9, were herein realized. Accordingly, N α -bis-dipicolinoyl-L-leucine methyl ester 1, the corresponding acid 2, its bis-DL-norvalyl methyl ester homologue 3, the acid 4 and hydrazide 5 analogues were conventionally prepared. The tetrachlorophthalic acid hydrazine conjugate 6, anisaldehyde hydrazone 7, the benzenetetracarboxylic acid and naphthalenetetracarboxylic acid bis-L-leucyl-DL-norvalyl cyclic octa bridged peptides 8 and 9 respectively, were newly synthesized via condensation of the hydrazide 5 with the corresponding aldehyde or anhydride. The chromatographic, IR, NMR and mass spectral analysis confirmed the identities of the synthesized compounds. Comparable to the two reference antiinflammatory drugs indomethacin ® and voltaren ® (100%), the determined antiinflammatory potency of the candidates (carrageenan ® induced paw edema in rats) revealed a general significant activity (66 - 94%), except for the practically inactive 6 (∼1.5 % activity). In particular, the potency of the (N α -dipicolinoyl)-bis-L-leucyl-DL-norvalyl anisaldehyde hydrazone 7 was of 94 and 87%, comparable to the reference drugs. However, 7 also showed 58% protection against ulcer formation, comparable to null for indomethacin ® . Additionally, an acceptable acute toxicity was observed (LD 50 : 2833 mg/kg, comparable to 2700 and 2850 for indomethacin ® and voltaren ® respectively).

Two new bimetallic complexes [Zn(phen) 3 ][Fe(CN) 5 (NO)] · 2 H 2 O · 0.25 MeOH, (1) and [(bipy) 2 (H 2 O)Zn(μ-NC)Fe(CN) 4 (NO)] · 0.5 H 2 O, (2), have been isolated (where phen = 1,10-phenanthroline and bipy = bipyridyl) and characterised by X-ray crystallography [as the 2 H 2 O · 0.25 CH 3 OH solvate for (1) and hemihydrate for (2)] infrared spectroscopy and thermogravimetric analysis. Substitution of phenanthroline for bipyridyl resulted in a cyano-bridged bimetallic species rather than two discrete mononuclear metal complexes. The bond angles of Fe-N-O were shown to be practically linear for both 1 [179.2(7)°] and 2 [178.3(3)°], and the Zn atoms have distorted octahedral geometry. The solvent molecules in both crystal lattices take part in forming hydrogen-bonded networks.

The intense long-wavelength absorption of Naphthol Green B at λ max = 712 nm is assigned to a ligand-to-metal charge transfer (MLCT) transition. LMCT excitation of the complex in aqueous solution leads to the reduction of Fe(III) to Fe(II) with a quantum yield of ϕ = 1.14×10 −3 at λ irr = 577 nm.

Single crystals of B-type thulium oxodisilicate Tm 2 Si 2 O 7 were obtained by the reaction of Tm, S and RbCl with the wall of a silica tube in an attempt to synthesize ternary alkalimetal thulium sulfides (e.g. Rb 3 Tm 7 S 12 ). It crystallizes triclinically in space group P1̄(a = 655.91(5), b = 659.04(5), c = 1195.32(9) pm, α = 94.361(8), β = 91.102(8), γ = 92.005(8)◦), with four formula units of Tm 2 Si 2 O 7 per unit cell. Instead of pyro-anionic [Si 2 O 7 ] 6 − groups the title compound contains both ortho-silicate tetrahedra [SiO 4 ] 4 − and catena-trisilicate units [Si 3 O 10 ] 8 −. Therefore the formula Tm 4 [Si 3 O 10 ][SiO 4 ] (Z = 2) appears more adequate. The four crystallographically independent Tm 3+ cations show coordination numbers from six to eight with distorted octahedral, bicapped trigonal prismatic and square antiprismatic oxygen coordination spheres.

Cr 3 C 2 was obtained from arc-melting of pellets made of carbon and chromium. The structure of Cr 3 C 2 was determined by single crystal X-ray diffraction (Pnma, Z = 4, a = 553.99(6), b = 283.27(4), c = 1149.4(1) pm, R1 = 0.019 and wR2 = 0.037 for all collected reflections). The crystal structure contains isolated carbon atoms which reside inside of trigonal prismatic voids of metal atoms. The compound exhibits temperature independent paramagnetism. The electronic structure of Cr 3 C 2 has been investigated using extended Hückel calculations.