Reversible Photochemical and Thermal Isomerization of Azaboratabisnorcaradiene to Azaborabenzotropilidene

Two new tricyclic 1,2‐azaboratabisnorcaradiene molecules ( 1 b and 2 b ) generated through the photoisomerization of N‐methyl‐2‐phenylimidazolyl‐chelated dimesitylboranes ( 1 a and 2 a ) have been found to undergo unusual photoisomerization, producing the first examples of 1,2‐azaborabenzotropilidenes ( 1 c and 2 c ), accompanied by a distinct color change, upon irradiation at 350 nm. Compounds 1 c and 2 c contain a conjugated alkylideneborane unit and can be fully reverted back to 1 b and 2 b , and subsequently to 1 a and 2 a upon heating. The mechanistic pathway of the new isomerism has been established to involve “walk” rearrangements by DFT computational studies.     

Heteroaryl substituted ansa‐titanocene anti‐cancer drugs derived from fulvenes and titanium dichloride

Starting from 2‐furylfulvene (1a) , 2‐thiophenylfulvene (1b) , and 1‐methyl‐2‐pyrrolylfulvene (1c), [1,2‐di(cyclopentadienyl)‐1,2‐di‐(2‐furyl)ethanediyl] titanium dichloride (2a) , [1,2‐di(cyclopentadienyl)‐1,2‐di‐(2‐thiophenyl)ethanediyl] titanium dichloride (2b) , and [1,2‐di(cyclopentadienyl)‐1,2‐bis‐(1‐methyl‐2‐pyrrolyl)ethanediyl] titanium dichloride (2c) were synthesized. When titanocenes (2a–c) were tested against pig kidney carcinoma cells (LLC‐PK), inhibitory concentrations (50%) of 4.5 × 10^?4 M , 2.9 × 10^?4 M and 2.0 × 10^?4 M respectively were observed. Copyright © 2005 John Wiley & Sons, Ltd.     

Benzolactams. 4. Reaction of 3',4'- or 4',5'-dialkoxy-substituted 1-(2'-Bromobenzyl)-2-ethoxycarbonyl-1,2,3,4-tetrahydroisoquinolines with alkyllithium. 1,2 and 1,4 additions of alkyllithium to benzolactams

Treatment of 1-(2'-bromo-3',4'-dialkoxybenzyl)-1,2,3, 4-tetrahydroisoquinoline carbamates, 1a,c, with excess alkyllithium gave 8-oxoberbines, 2a,c, which were successively attacked in situ with another molecule of alkyllithium to give 1,2 and/or 1,4 addition products. A primary alkyllithium, such as MeLi or BuLi, gave a 1,2 addition product, 8-methyleneberbine 9a or 8-butylideneberbine 3a. t-BuLi preferred 1,4 addition, followed by elimination of the alkoxy group, to give 9-tert-butyl-8-oxoberbine 6a or 7c. s-BuLi gave a mixture of 1,2 and 1,4 addition products, 1-[2'-(2' '-methylbutyryl)benzyl]-1,2,3,4-tetrahydroisoquinoline 4a and 9-s-butyl-8-oxoberbine 5a. Similar treatments of carbamate 1b having no alkoxy group at its 3' position gave 1,2 addition products, 8-butylideneberbine 3b, 1-[2'-(2' '-methylbutyryl)benzyl]-1,2,3, 4-tetrahydroisoquinoline 4b, and 1-(2'-pivaloylbenzyl)-1,2,3, 4-tetrahydroisoquinoline 6b, in all cases. Reactions of 1a with s-BuMgCl and isoPrMgCl also gave the 1,4 adduct, 5a, and its 9-isoPr analogue, 12a. Treatment of 9a with excess NaBH(4) in AcOH gave (+/-)-coralydine (10b).     

Reactions of Diferrocenylmorpholino- and -Methylsulfanyl-cyclopropenylium Salts with β-Dicarbonyl Compounds and Diethyl Malonate

2,3-Diferrocenyl-1-morpholinocyclopropenylium tetrafluoroborate reacts with ethyl acetoacetate, ethyl benzoylacetate, and diethyl malonate in the presence of triethylamine to yield 3-[acyl(ethoxycarbonyl)]-, 3-(diethoxycarbonyl)-methyl-3-morpholino-1,2-diferrocenylcyclopropenes (3a–c), and 3-[acyl(ethoxycarbonyl)]- and (diethoxycarbonyl)-methylidene-1,2-diferrocenylcyclopropenes (4a–c) in a ca. 1:1.5 ratio. 2,3-Diferrocenyl-1-methylsulfanylcyclopropenylium iodide with the same substrates affords compounds 4a,b (～10–15%), 3-[acyl(ethoxycarbonyl)]methyl-3-methylsulfanyl-1,2-diferrocenylcyclopropenes (5a,b) (～8–10%), 2-acyl-3,4-diferrocenyl-5-methylsulfanylcyclopentadienones (6a,b), ethyl 2-acyl-3,4-diferrocenyl-5-methylsulfanylpenta-2,4-dienoates (7a,b; 8a,b), and ethyl 3,4-diferrocenyl-2-methylsulfanyl-6-oxohexa(hepta)-2,4-dienoates (9a,b). The spatial structure of ethyl Z,E-3,4-diferrocenyl-2-methylsulfanyl-6-oxohepta-2,4-dienoate (9b) was established based on the data from x-ray diffraction analysis. Electrochemical properties of 3-[acyl(ethoxycarbonyl)]- and (diethoxycarbonyl)-methylidene-1,2-diferrocenylcyclopropenes (4a–c) are studied.     

螯形主体分子的设计、包结性能及其在细辛挥发油 有效成分选择分离中的应用

设计了两种新的具有螯形骨架的主体分子反式-1,2-二苯基-1,2-苊二醇(1)和顺式-1,2-二(1'-萘基)-1,2-苊二醇(2),主体(1),(2)可与许多有机小分子化合物形成配位包合物。用IR和粉末XRD表征了主体分子(1)和(2)的包结物,用^1NMR测定了包结物的主客体分子摩尔比：(1)·DMF(1:2),(1)·DMSO(1:2),(1)·THF(1:2),(1)·二氧六环(1:1),(1)·吡啶(1:1),(2)·DMF(1:1)和(2)·DMSO(1:1)。单晶X射线衍射分析了包结物的晶体结构,(1)·DMF：空间群Pnaa,a=0.9377(1)nm,b=1.4351(1)nm,c=4.0463(3)nm;(1)·DMSO：空间群Pbcn,a=1.6278(1)nm,b=1.0751(1)nm,c=1.4980(1)nm;(2)·DMF：P2~1/n,a=0.9796(1)nm,b=1.2377(1)nm,c=2.2344(3)nm,β=93.02(1)°;游离主体(1)：空间群P1,a=1.0461(1)nm,b=1.1213(1)nm,c=1.5496(1)nm,α=81.74(1)°,β=75.71(1)°,γ=89.00(1)°;分析了主体分子的刚性和柔韧性对包结性能的影响。并研究了主体分子(1)选择分离细辛挥发油,将顺甲基异丁香酚从挥发油中分离出来。     

Synthesis of Indeno[1,2‐d]pyrimidin‐5‐Ones and Their Fluorescence in Solid State

New fluorescent compounds, 2‐substituted indeno[1,2‐d]pyrimidin‐5‐ones ( 3a , 3b , 3c , 3d ) were synthesized in good yield by the reaction of 2‐[bis(methylsulfanyl)methylene]indan‐1,3‐dione ( 1 ) with the respective amidine derivatives [guanidine carbonate ( 2a ), acetamidine hydrochloride ( 2b ), S‐methylisothiourea sulfate ( 2c ), and S‐benzylisothiourea sulfate ( 2d )]. 4‐Substituted amino‐2‐aminoindeno[1,2‐d]pyrimidin‐5‐ones ( 7b , 7c , 7d ) were synthesized by a one‐pot reaction of 1 , 2a and the respective amine compounds ( 4b , 4c , 4d ) in pyridine. These fused pyrimidine derivatives showed fluorescence in the solid state.     

cis-[Pt(depe)(NCS)(SCN))]和cis-[Pt(dPr'pe)(NCS)]配合物的合成和分子结构

本文研究了在1:1丙酮-水混合溶剂中回流条件下, cis-[Pt(diphos)Cl2]与NaCNS之间的取代反应, 第一次合成了CNS的混合键合异构体的depe铂配合物cis-[Pt(depe)(NCS)(SCN)], 进行了分子结构测定, 属单斜晶系, 空间群为P21/n晶胞参数: a=7.296(5), b=14.434(4), c=18.042(4)A, β=95.72(8)°,V=1890.7A^, Z=4, Rf=0.0564, 在相同条件下用dPr'pe作了对照实验, 得到的是cis-[Pt(dPr'pe)(NCS)2], 属单斜晶系, 空间群为Cc, 晶胞参数, a=12.279(6),b=9.330(8), c=20.102(7)A, β=108.90(9), V=2179.0(3)A^3, Z=4,Rf=0.0419. 此外, 还从双膦烷基的空间效应和电子效应讨论了对取代反应产物的影响。     

Hydrogen-shift isomerism: mass spectrometry of isomeric benzenesulfonate and 2-, 3- and 4-dehydrobenzenesulfonic acid anions in the gas phase

The isomeric 3- and 4-dehydrobenzenesulfonic acid anions b and c were prepared by collision induced dissociation (CID) of the [M - H](-) ions of isomeric sulfobenzoic acids obtained by negative electrospray ionization (ESI). The CID spectra (MS(3)) of anions b and c are different from each other, and both are different from that of the isomeric benzenesulfonate anion a, obtained from benzenesulfonic acid. The stability of ions b and c shows that 1,2-proton transfer does not take place in this system under the conditions of the CID experiment. Density functional (DFT) calculations at B3LYP/6-31+G(2d,p) level of theory show that benzenesulfonate anion a is the most stable isomer, and the energies of isomers b and c are higher by more than 65 kcal mol(-1). The calculated energies of the transition states involved in the 1,2-hydrogen migration leading to the interconversion of the isomeric anions are very high (>120 kcal mol(-1)relative to ion a, barrier energies >55 kcal mol(-1)), much higher than those of transition structures leading to fragmentation. This situation does not allow isomerization of ions b and c to a, under the conditions of the CID experiments. The isomeric 2-dehydrobenzenesulfonic acid anion isomerizes to the benzenesulfonate anion a by a facile proton transfer from the SO(3)H group to the adjacent position 2. The results of this work indicate that the gas phase deprotonation of meta- and para-sulfobenzoic acids is a kinetically controlled process.     

Synthesis of some 2-(heteroarylamino)benzimidazoles and their cyclization with phosgene

2-(Benzimidazol-2-ylamino)pyridine (4a) , 2-(benzimidazol-2-ylamino)pyrazine (4b) , and 2-(benzimidazol-2-ylamino)thiazole (4c) underwent a ring-closure reaction on treatment with phosgene affording 6H-pyrimido-[1′,2′:5,4][1,3,5]triazino[1,2-a]benzimidazol-6-one (1a) , 6H-pyrazino[1′,2′:5,4][1,3,5]triazino[1,2-a]benzimidazol-6-one (1b) , and 5H-thiazolo[2′,3′:4,5][1,3,5]triazino[1,2-a]benzimidazol-5-one (1c) respectively. The structure of these hitherto unknown heterocyclic systems was confirmed by their ir and mass spectra.     

A competitive molecular recognition study: syntheses and analysis of supramolecular assemblies of 3,5-dihydroxybenzoic acid and its bromo derivative with some N-donor compounds

A molecular recognition study of 3,5-dihydroxybenzoic acid (1) and its bromo derivative 4-bromo-3,5-dihydroxybenzoic acid (2) with the N-donor compounds 1,2-bis(4-pyridyl)ethene (bpyee), 1,2-bis(4-pyridyl)ethane (bpyea), and 4,4'-bipyridine (bpy) is reported. Thus, the syntheses and structural analysis of molecular adducts 1 a-1 c (1 with bpyee, bpyea, and bpy, respectively) and 2 a-2 c (2 with bpyee, bpyea, and bpy, respectively) are discussed. In all these adducts, recognition between the constituents is established through either O--H...N and/or O--H...N/C--H...O pairwise hydrogen bonds. In all the adducts both OH and COOH functional groups available on 1 and 2 interact with the N-donor compounds, except in 2 a, in which only COOH (COO-) is involved in the recognition process. The COOH moieties in 1 a, 1 b, and 2 b form only single O--H...N hydrogen bonds, whereas in 1 c and 2 c, they form pairwise O--H...N/C--H...O hydrogen bonds. In addition, subtle differences in the recognition patterns resulted in the formation of cyclic networks of different dimensions. In fact, only 1 c forms a four-molecule cyclic moiety, as was already documented in the literature for this kind of assemblies. All complexes have been characterized by single-crystal X-ray diffraction. The supramolecular architectures are quite elegant and simple, with stacking of sheets in all adducts, but a rather complex network with a threefold interpenetration pattern was found in 2 c.     

Synthesis, electrochemistry, and gas-phase photoelectron spectroscopic and theoretical studies of 3,6-bis(perfluoroalkyl)-1,2-dithiins

3,6-bis(trifluoromethyl)- and 3,6-bis(pentafluoroethyl)-1,2-dithiin (1a,b), the first known perfluoroalkyl-substituted 1,2-dithiins, were synthesized from (Z,Z)-1,4-bis(tert-butylthio)-1,3-butadiene (2) to evaluate the effects of electron-withdrawing groups on the ionization and oxidation potentials of 1,2-dithiins. Analysis of the photoelectron spectra of 1a and 1b provided a basis for assigning orbital compositions. Ab initio calculations on these compounds showed that they adopt a twist geometry as does 1,2-dithiin (1c) itself. Cyclic voltammetric studies on 1a and 1b revealed a reversible oxidation followed by an irreversible oxidation at much more positive potentials than for 1,2-dithiin and 3,6-dimethyl-1,2-dithiin (1d). The oxidation potentials determined electrochemically do not correlate with the ionization potentials determined by photoelectron spectroscopy. This result supports the previously advanced hypothesis that there is a geometry change on electrochemical oxidation leading to a planar radical cation.     

Studies with Heterocyclic β‐Enaminoniriles: A Simple Route for the Synthesis of Polyfunctionally Substituted Thiophene,Imidazo[1,2:1′,6′]pyrimido[5,4‐b]thiophene and Thieno[3,2‐d]pyrimidine Derivatives

Reaction of 3,5‐diaminothiophene‐2‐carbonitrile derivatives 3a‐c with ethoxycarbonylmethyl isothiocyanate and/or N‐[bis(methylthio)methylene]glycine ethyl ester led to formation of 7‐substituted‐8‐amino‐5‐thioxo‐6H‐imidazo[1,2:1′,6′]pyrimido[5,4‐b]thiophene‐2(3H)‐one derivatives 6a‐c and 7‐substituted‐8‐amino‐5‐(methylthio)imidazo[1,2:1′,6′]pyrimido[5,4‐b]thiophene‐2(3H)‐one 7a‐c , respectively. Also, the synthetic potential of the β‐enaminonitrile moiety in 3a‐c has been explored; it proved to be a promising candiate for the synthesis of 1,6‐disubstituted‐2,4‐diamino‐7,8‐dihydro‐8‐oxopyrrolo[1,2‐a]thieno[2,3‐e]pyrimidine derivatives 10a‐f and pyrido[2′,3′:6,5]pyrimido[3,4‐a]benzimidazole derivatives 12a,b .     

Structural characterization of the picket fence (TpivPP) porphyrins Co(TpivPP), Co(TpivPP)(NO2)(1-MeIm), and Co(TpivPP)(NO2)(1,2-Me2Im)

The compounds Co(TpivPP) (1), Co(TpivPP)(NO2)(1-MeIm) (2), and Co(TpivPP)(NO2)(1,2-Me2Im) (3) have been synthesized (TpivPP = meso-tetrakis(alpha, alpha, alpha, alpha-o-pivalamidophenyl)porphyrinato dianion), and their structures have been determined with single-crystal X-ray diffraction methods. 1: a = 17.578(1) A, b = 17.596(1) A, c = 20.639(1) A, beta = 115.03(1) degrees, P2(1)/c, Z = 4, T = -120 degrees C. 2: a = 18.522(4) A, b = 18.942(4) A, c = 18.177(4) A, beta = 90.68(3) degrees, C2/c, Z = 4, T = -70 degrees C. 3: a = 18.998(4) A, b = 19.187(4) A, c = 18.000(4) A, beta = 90.96(3) degrees, C2/c, Z = 4, T = -120 degrees C. Compounds 2 and 3 have crystallographically imposed 2-fold axes. In 2 and 3, which represent R-state (relaxed) and T-state (tense) models, respectively, for hemoglobin, the NO2 ligand is bound on the "picket" side to the Co atom, and either 1-MeIm (for 2) or 1,2-Me2Im (for 3) is bound to the Co atom at the sixth coordination site on the sterically unhindered side of the molecule. The average deviations of atoms from the 24-atom porphyrin core are 0.031, 0.129, and 0.117 A for 1, 2, and 3, respectively. The Co atom is -0.043(1) A out of the mean 24-atom porphyrin plane toward the 1-MeIm ligand in 2 and -0.089(1) A out of the plane toward the 1,2-Me2Im ligand in 3. The bonds of both axial ligands in the R-state model 2, 1.898(4) A for Co-N(O2) and 1.995(4) A for Co-N(base), are shorter than the corresponding bonds in the T-state model 3, 1.917(4) A for Co-N(O2) and 2.091(4) A for Co-N(base).     

新型吡咯并三嗪酮类PARP-1抑制剂的设计、合成及生物活性

分别以5-溴-2-氟苯甲腈(1a)和3-溴苯甲腈(1b)为原料,经Sonogashira偶联,脱三甲基硅基保护基,三分子偶联及水解等5步反应制得中间体2-氟-5-［(4-氧代-3,4-二氢吡咯［1,2-d］［1,2,4］三嗪-1-基)甲基］苯甲酸（6a)和3-[(4-氧代-3,4-二氢吡咯［1,2-d］［1,2,4］三嗪-1-基)甲基］苯甲酸（6b）。环烷基甲酸经酰氯化,缩合和脱Boc保护基3步反应制得环烷基哌嗪-1-基甲酮(7a~7c)。 6a与NCS（1 eq.）反应制得5-［(6-氯-4氧代-3,4二氢吡咯［1,2-d］［1,2,4］三嗪-1-基)甲基］-2氟 苯甲酸(6c); 6a与NCS(2 eq.)反应制得5-［(6,7-二氯-4氧代-3,4二氢吡咯［1,2-d］［1,2,4］三嗪-1-基)甲基］-2氟-苯甲酸(6d)。 6a~6d, 6a~6c分别与7a~7c和1-（2-嘧啶基）哌嗪在TBTU（缩合剂）,DIPEA（碱）的作用下合成了13个新型吡咯并三嗪酮类PARP-1抑制剂(8a~8m),其结构经¹HNMR和MS(ESI)表征。采用Alarm blue法研究了8a~8m对肿瘤细胞MDA-MB-436的抑制活性(IC₅₀)。结果表明：8f, 8g, 8i和8j对MDA-MB-436有较强的抑制活性（IC₅₀=30.5~69.3 nmol·L^-1）。     

Preparation of some substituted imidazo[1,2-a]pyridine derivatives

2-Bromopyridine derivatives 2a-2c were prepared. Compounds 2b and 2c and ammonia yielded aminopyridines 3b and 3c which were converted to imidazo[1,2-a]pyridine derivatives 4b and 4c . Compound 4b was nitrated giving the analogue 5b of metronidazole 1 .     

Neutral pentacoordinate silicon fluorides derived from amidinate, guanidinate, and triazapentadienate ligands and base-induced disproportionation of Si2Cl6 to stable silylenes

Pentacoordinate silicon fluorides L(1)SiF(3) (2a), L(2)SiF(3) (2b), and (L(3)SiF(2))(2) (2c)(2) based on amidinate (L(1) = PhC(N(t)Bu)(2)), guanidinate (L(2) = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate), and triazapentadienate (L(3) = NC(NMe(2))NC(NMe(2))NAr; Ar = 2,6-(i)Pr(2)C(6)H(3)) ligands were prepared by fluorination of the corresponding chlorosilanes L(1)SiCl(3) (1a), L(2)SiCl(3) (1b), and L(3)SiCl(2) (1c) with Me(3)SnF at ambient temperature. Compounds 1b, 1c, 2a, 2b, and (2c)(2) were characterized by (1)H, (13)C, (19)F, and (29)Si NMR spectroscopic studies. Molecular structures of 1b, 1c, 2a, and (2c)(2) were determined by single crystal X-ray structural analysis. Invariom refinement involving non-spherical scattering factors of the Hansen-Coppens multipole model was performed for 1b. Compound L(3)SiF(2) (2c) is dimeric both in the solid state and in solution, whereas its chloro-analogue 1c is monomeric. The attempted synthesis of diamidinatotetrachlorodisilane by reaction of lithium amidinate with Si(2)Cl(6) led to the formation of the silane (1a) and the silylene L(1)SiCl (3). Reaction of Si(2)Cl(6) with N-heterocyclic carbenes (NHC) afforded NHC adducts of dichlorosilylene and SiCl(4). A one pot method for the preparation of base-stabilized silylenes from Si(2)Cl(6) is discussed.     

Synthesis of some isomeric quinoxaline derivatives with 6‐azauracil cycle

By diazotization of 3‐(2‐aminophenyl)‐1,2‐dihydroquinoxaline 1c, its 3‐(4‐aminophenyl)‐isomer 2c , 3‐(2‐aminobenzyl)‐1,2‐dihydroquinoxaline‐2‐one 3c and its 3‐(4‐aminobenzyl)‐isomer 4c and by azo coupling of formed diazonium salts with ethyl cyanoacetylcarbamate, corresponding hydrazones ld‐4d were prepared. Cyclization of these compounds afforded compounds containing two heterocyclic rings with acidic N‐H groups in their molecules: 3‐[2‐(5‐cyano‐6‐azauracil‐1‐yl)‐phenyl]‐1,2‐dihydroquinoxaline‐2‐one 1e , its 4‐isomer 2e , 3‐[2‐(5‐cyano‐6‐azauracil‐1‐yl)‐benzyl]‐1,2‐dihydroquinoxaline‐2‐one 3e and its 4‐isomer 4e . The aminoderivative 1c was prepared by the reaction of N‐acetylisatine with o‐phenylenediamine and by hydrolysis of prepared N‐acetylderivative 1a . The aminoderivative 2c was prepared by the condensation of 4‐acetylaminophenylglyoxylic acid with o‐phenylenediamine and by hydrolysis of prepared N‐acetylderivative 2a . The aminoderivative 3c was prepared by the condensation of 2‐nitrophenylpyruvic acid with o‐phenylenediamine and by the reduction of the formed nitroderivative 3b and finally starting aminoderivative 4c was obtained by the condensation of o‐phenylenediamine with 4‐aminophenylpyruvic acid.     

Metal complexes with 2,3-bis(diphenylphosphino)-1,4-diazadiene ligands: synthesis,structures, and an intramolecular metal-mediated [4 + 2] cycloaddition employing a benzene ring as a dienophile

2,3-Bis(diphenylphosphino)-1,4-diazadienes RN=C(PPh2)-C(PPh2)=NR (1a, R = 4-tolyl; 1b, R = 4-tert-butylphenyl; 1c, R = mesityl) were used as novel ligands for transition metals. The metal complexes [(1c)Mo(CO)4] (2a), [(1c)[Mo(CO)4]2] (2b), [(1a)Cu(Cl)(PPh3)] (3), and [(1b)[(NiBr2(THF))]2] (4) were characterized by elemental analysis, MS, and 31P[1H], 1H, and 13C NMR spectra (except the paramagnetic complex 4). Additionally, the molecular structure of the complexes in the solid state was determined by single-crystal X-ray diffraction. In 2a and 2b the chelating ligand coordinates via the N,P donor set, whereas in 3 the chelating ligand coordinates via the two P atoms. 4 contains a square-planar (P,P)NiBr2 moiety on the one side of the bridging ligand 1b. On the opposite side the 1,2-dimine unit bonds to another Ni center having octahedral geometry. The bulkier ligand 1c reacts to form the mononuclear compound 5. X-ray diffraction analysis of single crystals shows that 5 contains a quinoxaline derivative with a cyclohexa-1,3-diene ring in the peripheral position. Furthermore, it contains a bis(diphenylphosphino)-ethylene unit coordinating the NiBr2. This arrangement is the result of an intramolecular [4 + 2] cycloaddition between the 1,2-diimine unit (as diheterodiene) and the benzene ring of the 4-tolyl-N substituent (as dieneophile). The same type of ring-closing reaction followed by a tautomerization reaction to form the mononuclear compound 6 occurred by dissolution of the binuclear complex 4 in methanol. This reaction can be used as a simple method for the synthesis of novel 1,2-bis(diarylphosphanyl)ethylenes containing a quinoxaline backbone.     

Synthesis, molecular structures, and chemistry of some new palladium(II) and platinum(II) complexes with pentafluorophenyl ligands

A series of palladium(II) and platinum(II) complexes possessing pentafluorophenyl ligands of the general formula [M(L-L)(C6F5)Cl][space](M = Pd 3; L-L=tmeda (N,N,N',N',-tetramethylethylenediamine) a; 1,2-bis(2,6-dimethylphenylimino)ethane) b; dmpe (1,2-bis(dimethylphosphino)ethane) c; dcpe (1,2-bis(dicyclohexylphosphino)ethane) d; Pt ; L-L=tmeda a; 1,2-bis[3,5-bis(trifluoromethyl)phenylimino]-1,2-dimethylethane b; dmpe c; dcpe d) were readily synthesized from the dimer [M(C6F5)(tht)(mu-Cl)2] (M=Pd 1b, Pt 2b; tht=tetrahydrothiophene) and the corresponding bidentate ligand. In the case of palladium, the corresponding iodo analogues (6a-c) were readily synthesized in a one-pot reaction from [Pd2(dba)3], iodopentafluorobenzene, and the appropriate ligand. The platinum complexes 4c-d were then converted to the water complexes [Pt(L-L)(C6F5)(OH2)]OTf (L-L =dmpe 7a; dcpe 7b)via reaction with AgOTf in the presence of water. Attempts to convert the palladium complexes 3c-d to the corresponding water complexes resulted in the disproportionation of the intermediate water complex to form [Pd(L-L)(C6F5)2] (L-L=dmpe 8) or [Pd(L-L)2][OTf]2(L-L=dcpe 9). Upon standing in solution for prolonged periods, complex 7a undergoes an identical disproportionation reaction to the Pd analogues to form [Pt(L-L)(C6F5)2] (L-L=dmpe 10). Complexes 4c and 4d were converted to the corresponding hydrides (11b-c, respectively) using two different hydride sources: 11a was formed by the reaction of with NaBH4 in refluxing THF, while 11b was synthesized in near quantitative yield using [Cp2ZrH2] in refluxing THF. Attempts to synthesize eta2-tetrafluorobenzyne complexes [Pt(L-L)(C6F4)] (L-L=dmpe, dcpe) from reaction of 11a-b with butyllithium were unsuccessful. The molecular structures of 3a,4a, 4c, 4d, 6b, 7a, 8, 11b and have been determined by X-ray crystallographic studies, and are discussed.     

Synthesis and Antitumor Activity of Heterocycles Related to Carbendazim

Three types of compounds were synthesized from carbendazim ( 1 ), a benzimidazole derivative (Scheme 1 ). They included a group of esters at N1 prepared by treating carbendazim with isocyanates bearing ester groups ( 2a , 2b , 2c ), carboxyalkyl‐1,2,3,4‐tetrahydro‐s‐triazino[1,2‐a]benzimidazole‐2,4‐dione esters ( 3a and 3b , 3d and 3c derived from 3a . The antitumor potencies of the N1 esters were in the range of 7 to 40 μM, which compares favorably with carbendazim, but their water solubilities were low. The s‐triazine derivatives showed activity against pancreatic tumor cells, and one of them ( 3b ) was active in mice, but they were not effective against other tumor types. Treatment of carbendazim with 3‐bromopropionyl chloride produced 1‐methoxycarbonyl‐4‐oxo‐1,2,3,4‐tetrahydropyrimido[1,2‐a]benzimidazole ( 4 ), which gave 1‐(3‐aminopropionyl)benzimidazole 2‐methylcarbamates, substituted on the amino nitrogen ( 5a , 5b , and 5d ), when treated with amines. These products showed some antitumor activity in cell cultures, and an ethoxy derivative ( 5c ), obtained by treating 1‐methoxycarbonyl‐4‐oxo‐1,2,3,4‐tetrahydropyrimido[1,2‐a]benzimidazole with sodium ethoxide, was active in the 67–150 μM range. Some of the new compounds had good water solubility. Carbendazim kills tumor cells by inhibiting tubulin; however, s‐triazine 3b , which differs from it in size and functional groups, does not act by this mechanism.