Transfer hydrogenation processes to mu(3)-alkylidyne groups on the organotitanium oxide [Ti(3)Cp*O(3)

The photochemical treatment of mu(3)-alkylidyne complexes [[TiCp*(mu-O)](3)(mu(3)-CR)] (R=H (1), Me (2), Cp*=eta(5)-C(5)Me(5)) with the amines (2,6-Me(2)C(6)H(3))NH(2), Et(2)NH, and Ph(2)NH and the imine Ph(2)C=NH leads to the partial hydrogenation of the alkylidyne moiety that is supported on the organometallic oxide, [Ti(3)Cp*O(3)], and the formation of new oxoderivatives [[TiCp*(3)(mu-CHR)(R'NR")] (R"=2,6-Me(2)C(6)H(3), R'=H, R=H (3), Me (4); R'=R"=Et, R=H (5), Me (6); R'=R"=Ph, R=H (7), Me (8)) and [[TiCp*(mu-O)](3)(mu-CHR)(N=CPh(2))] (R=H (9), R=Me (10)), respectively. A sequential transfer hydrogenation process occurs when complex 1 is treated with tBuNH(2), which initially gives the mu-methylene [[TiCp*(mu-O)](3)(mu-CH(2))(HNtBu)] (11) complex and finally, the alkyl derivative [[TiCp*(mu-O)](3)(mu-NtBu)Me] (12). Furthermore, irradiation of solutions of the mu(3)-alkylidyne complexes 1 or 2 in the presence of diamines o-C(6)H(4)(NH(2))(2) and H(2)NCH(2)CH(2)NH(2) (en) affords [[TiCp*(mu-O)](3)(mu(3)-eta(2)-NC(6)H(4)NH)] (13) and [[TiCp*(mu-O)](3)(mu(3)-eta(2)-NC(2)H(4)NH)] (14) by either methane or ethane elimination, respectively. In the reaction of 1 with en, an intermediate complex [[TiCp*(mu-O)](3)(mu-CH(2))(NHCH(2)CH(2)NH(2))] (15) is detected by (1)H NMR spectroscopy. Thermal treatment of the complexes 4-10 quantitatively regenerates the starting mu(3)-alkylidyne compounds and the amine R'(2)NH or the imine Ph(2)C=NH; however, heating of solutions of 3 or 4 in [D(6)]benzene or a equimolecular mixture of both at 170 degrees C produces methane, ethane, or both, and the complex [[TiCp*(mu-O)](3)[mu(3)-eta(2)-NC(6)H(3)(Me)CH(2)]] (16). The molecular structure of 8 has been established by single-crystal X-ray analysis.     

New 1,2,3‐triazolo[4,5‐e]1,2,4‐triazolo[4,3‐c]pyrimidine derivatives II

The 7‐chloro‐3‐(2‐chlorobenzyl)‐ and 7‐chloro‐3‐(2‐fluorobenzyl)‐1,2,3‐triazolo[4,5‐d]pyrimidines ( 1 and 4 ), by nucleophilic replacement with some hydrazides, gave the corresponding 7‐hydrazidoderivatives ( 2a‐e and 5a‐e ). These, by heating in Dowtherm, underwent an intramolecular cyclization to form the new tricyclic 7‐substituted‐3‐(2‐chlorobenzyl)‐ and 3‐(2‐fluorobenzyl)‐1,2,3‐triazolo[4,5‐e]1,2,4‐triazolo[4,3‐c]pyrimidines ( 3a‐d and 6a‐d ). The 7‐hydrazino‐3‐(2‐chlorobenzyl)‐ and 7‐hydrazino‐3‐(2‐fluorobenzyl)‐triazolo‐pyrimidines ( 9a and 9b ) were also prepared via the corresponding mercapto ( 7a and 7b ) and thiomethyl ( 8a and 8b ) derivatives.     

Synthesis of novel 1-(2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)-uracil and -thymine, and their corresponding S-oxidized derivatives

On the basis of molecular variations on isosteric replacements from the prototype 1-(2,3-dihydro-5H-1,4-benzodioxepin-3-yl)-5-fluorouracil a series of 3-(2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)-uracil or -thymine O,N-acetals was prepared. The nature of the cis- and trans-sulfoxide isomers was established by means of their conformational analyses carried out with Sybyl and after comparing the theoretical results with the ¹H NMR responses of the target molecules. (RS)-3-(1,1-Dioxo-2,3-dihydro-5H-4,1-benzoxathiepin-3-yl)thymine and (1S*,3S*)-1-(1-oxo-3,5-dihydro-2H-4,1-benzoxathiepin-3-yl)thymine were found to be inhibitors of the MCF-7 cell growth.     

The oxidative addition of diphenylphosphine and monophenylphosphine to the electron-rich rhenium-rhenium triple bond. The isolation and characterization of compounds that contain the four-center Re(μ-X)(μ-PR2)Re cluster (X=halide)

Diphenylphosphine oxidatively adds to the ReRe bonds of Re₂ X ₄(-dppm)₂ (X=Cl or Br; dppm=Ph₂PCH₂PPh₂) and Re₂Cl₄(-dpam)₂ (dpam=Ph₂AsCH₂AsPh₂) to afford the dirhenium(III) complexes Re₂(-X)(-PPh₂)HX ₃(-LL)₂. The dppm complexes have also been prepared from the reactions of Re₂(-O₂CCH₃)X ₄(-dppm)₂ with Ph₂PH, and a similar strategy has been used to prepare Re₂(-Cl)(-PPh₂)HCl₃(-dmpm)₂ (dmpm=Me₂PCH₂PMe₂) from Re₂(-O₂CCH₃)Cl₄(dmpm)₂. Phenylphosphine likewise reacts with Re₂ X ₄(-dppm)₂ to give Re₂(-X)(-PHPh)HX ₃(-dppm)₂. An X-ray crystal structure determination on Re₂(-Cl)(-PPh₂)HCl₃(-dppm)₂ confirms its edge-shared bioctahedral structure. This complex crystallizes in the space group (No. 148) witha=21.699(3) Å, =84.50(4)°,V=10084(5) ų, andZ=6. The structure was refined toR=0.049 (R _w 0.069) for 5770 data withI>3.0(I). The Re-Re distance is 2.5918(7) Å. Oxidation of the bromide complex Re₂(-Br)(-PPh₂)HBr₃(-dppm)₂ with NOPF₆ produces the unusual dirhenium(III, II) cation [Re₂(-H)(-Br)[P(O)Ph₂]Br₂(NO)(-dppm)₂]⁺ which has been structurally characterized as its perrhenate salt, [Re₂(-H)(-Br)[P(O)Ph₂]Br₂(NO)(-dppm)₂]ReO₄ · 2CH₂Cl₂. This complex crystallizes in the space group (No. 2) witha=14.187(7) Å,b=16.419(5) Å,c=16.729(5) Å, =98.76(2)°, =110.11(3)°, =104.66(3)°,V=3414(6) ų,Z=2. The structure was refined toR=0.040 (R _w =0.051) for 5736 data withI>3.0(I). The presence of a phosphorus-bound [P(O)Ph₂]^– ligand, a linear nitrosyl and a bridging hydrido ligand has been confirmed. The Re-Re distance is 2.6273(8) Å.     

Phase morphology of hydrolysable polyurethanes derived from aqueous dispersions

Biodegradable polyurethanes are an interesting alternative to many applications that involve plastics since they can minimize environmental problems caused by the low rates of natural degradation of synthetic polymers. In addition, since waterborne polyurethanes are based on aqueous dispersions, they restrict the use of organic solvents during processing and application of the polymer, thus contributing furthermore to reduce environmental damage. In this work, aqueous anionic polyurethane dispersions (PUD) with tailorable susceptibility for hydrolysis were synthesized by progressively replacing polypropylene glycol (PPG) with a biodegradable polycaprolactone diol (PCL) as soft segments. The hard segments were formed by extending isophorone diisocyanate (IPDI) with hydrazine (HZ). Dimethylol propionic acid (DMPA) was used as ionic center and triethyl amine (TEA) as neutralizer. The degree of phase separation was evaluated mainly by infrared spectroscopy (FTIR) and small angle X-ray scattering (SAXS). The results indicated that phase separation between hard and soft segments of poly(ester-urethane) is more significant than that of poly(ether-urethane). Data obtained from SAXS experiments indicated that phase separation within soft domains can also be present in samples containing both polyester and polyether soft segments. Hydrolytic degradation of the polymers in buffer solution of pH 7.4 and alkaline solution was performed as an initial test. The results showed that the fraction of polyester soft segments in the polyurethanes can be used to tailor the susceptibility of the materials to hydrolytic attack. Polyurethanes having higher contents of polyester were more promptly hydrolytically degraded than polyurethanes containing only polyether segments.     

Changes in the reactivity of the fluorescent reagents carbazole-9-carbonyl chloride and 9-carbazolylacetic acid in the presence of cyclodextrins

Carbazole-9-carbonyl chloride (C9CC) and 9-carbazolylacetic acid (9CAA) were selected as model fluorescent reagents. The effect of different chemically modified cyclodextrins (CDs) added to the aqueous solutions of these reagents was studied in water and in buffered aqueous solutions at pH 4.5 and 8.8. The CDs employed were 2-hydroxypropyl-β-cyclodextrin (HP-βCD), 2,3-di-O-methyl-β-cyclodextrin (DM-βCD) and 2,3,6-tri-O-methyl-β-cyclodextrin (TM-βCD). The inclusion of these reagents inside the cavities of the CDs was verified and this process can affect the derivatization reaction because CDs can modify the reactivity of the guest molecules. The basic conditions necessary for the derivatization reaction between C9CC and amines lead to the formation of carbazole anion through hydrolysis followed by decarboxylation. In the presence of CDs, the hydrolysis-decarboxylation of carbazole-9-carbonyl chloride is faster than in buffered aqueous homogeneous solutions. The behaviour observed for these reagents in aqueous solutions of CDs was compared to the one observed in basic ethanolic solutions. These changes are particularly noticeable in the case of 2,3-di-O-methyl-β-CD and 2-hydroxypropyl-β-CD. The characteristics of the fluorescent reagents are compared to carbazole and 9-methylcarbazole as model compounds. This paper was presented at XIIIth International Cyclodextrin Symposium. Torino, Italy, May 14–17, 2006.     

An intraindividual study of the characteristics of erythema induced by bath and oral methoxsalen photochemotherapy and narrowband ultraviolet B

We compared the characteristics of psoralen and ultraviolet A (PUVA) erythema in skin photosensitized by bath or oral methoxsalen in 20 subjects. Erythema was assessed visually and with a reflectance instrument at 24 h intervals for 7 days. In addition, narrowband ultraviolet B (TL-01 UVB) erythema was examined in 19 of these subjects at 4, 8, 12, 24, 48 and 72 h and in another nine subjects at 12, 15, 18, 21 and 24 h. Both bath and oral PUVA exhibited broad erythemal peaks beyond 72 h. For topical PUVA the lowest minimal phototoxic dose (MPD) occurred at 120 and 144 h (P = 0.01 and 0.03 compared with 72 h). Oral PUVA erythema peaked earlier at 96 h: the MPD was significantly lower at 96, 120 and 144 h compared with 72 h (P = 0.001, 0.01 and 0.02, respectively). At 120 h, bath PUVA had a significantly steeper slope compared with oral PUVA. The TL-01 UVB minimal erythema dose was significantly lower at 12 h compared with 24 h (P = 0.019). The majority of subjects were at maximal erythema at 12 h (22 of 28) and 15 h (eight of nine). Our results suggest that peak erythema for bath PUVA, oral PUVA and TL-01 UVB occurs at 120, 96 and 12-15 h, respectively.     

Crystal Structures of Twisted Di(2-Pyridyl)ketone and Planar Azo-di(2-Pyridine) and Their Discussion Based on PM3 Enthalpy Hypersurfaces for the Isoelectronic Molecules

Single crystal structure determinations prove the two pyridine substituents in di(2-pyridyl)ketone (H₄C₄NC)₂C=O to be twisted out of the carbonyl skeleton plane by torsion angles (OCCN) of 41° and –163°, in contrast to their planar arrangement in azo-di(2-pyridine) H₄C₄NC)-N=N-(CNC₄H₄). In order to rationalize the surprising difference between the two isoelectronic molecules, approximate PM3 enthalpy of formation hypersurfaces have been calculated for each of the two ring torsions, which are assumed to be the dominant ones among the 3N – 6 = 60 degrees of freedom. For both the ketone and the azo derivative, global minima are calculated, the torsion angles of which deviate from the crystal structure results, and, therefore, support the assumption that both the experimentally determined twisting of di(2-pyridyl)ketone as well as the flattening of azo-di(2-pyridine) might be affected by the crystal packing.     

Quantitative determination of formic acid in apple juices by H NMR spectrometry

A quantitative determination method of formic acid in apple juices is proposed by means of the proton nuclear magnetic resonance (¹H NMR) technique. Formic acid gives a singlet signal at the 8.2-8.4 ppm interval of the spectrum, and its area is used to determine the concentration of the acid. 1,3,5-Benzenetricarboxylic acid is added to the juice as an internal standard. Since the chemical shift of both species varies with the pH, ascorbic acid is also added to adjust it at 2.74 and to avoid the overlapping of the signals. Recoveries between 95 and 109% are obtained when the standard addition method is applied to the juices of five different cider apple varieties. The coefficient of variation obtained is 3.9% for intra-day repeatability (n = 5), and 4.6% for inter-day repeatability (n = 10). The limit of detection is 1.49 mg/l, calculated from “3S_y/x + intercept”. The described method is direct and no previous derivatization is needed.     

Pentanuclear Ba(II) complex of a macrocyclic ligand

We report here the first pentanuclear Ba(II) complex of a new tri-aza, tri-oxa macrocycle with two carboxymethyl "arms" pending from two N atoms, H2L2. The crystal structure corresponds to the formula [Ba5(H0.375L2)4(ClO4)(CH3CH2OH)(H2O)2](ClO4)2.5 x 9.5H2O and reveals the presence of four molecules of the ligand surrounding five Ba(II) ions, giving rise to an unusual structure with the metal ions inside a spherical organic cavity.