Dimeric samarium(III) alkoxides bearing N2O2 tetradentate Schiff bases and their utility for the catalytic epoxidation of trans-chalcone

Two anhydrous, dimeric samarium(III) complexes bearing a bulky μ-alkoxide (diphenylmethoxide) ligand and different “saturated” tetradentate Schiff bases {bis-5,5′-(1,3-propanediyldiimino)-2,2-dimethyl-4-hexene-3-onato and bis-5,5′-(2,2-dimethyl-1,3-propanediyldiimino)-2,2-dimethyl-4-hexene-3-onato} were synthesized and fully characterized. The complexes differ only in alkyl substitution at the three-carbon amino linker between the ketoiminato halves, with one having a CH₂ group and the other a C(CH₃)₂ substituent along the free-ligand idealized mirror plane. Both metal-containing molecules were isolated in high-yields from direct alcoholysis of the corresponding 5-coordinate, mononuclear complexes and their catalytic activity for the epoxidation of 1,3-diphenyl propenone (trans-chalcone), an α,β-unsaturated ketone, investigated.     

Synthesis and structural characterization of two five coordinate aluminum alkyl and bis(trimethylsilyl)amino complexes bearing acyclic tetradentate Schiff bases

Two acyclic Schiff-base ligands, bis-5,5′-(1,3-propanediyldiimino)-2,2-dimethyl-4-hexene-3-one and bis-5,5′-(1,3-ethanediyldiimino)-2,2-dimethyl-4-hexene-3-one, were used to complex homoleptic triethylaluminum and tris[bis(trimethylsilyl)amino]aluminum, respectively. The acid–base reactions proceeded in excellent yields with elimination of ethane or bis(trimethylsilyl)amine during in situ deprotonation of the protio Schiff-base. The colorless aluminum complexes crystallized from n-pentane and were characterized by standard methods including single crystal X-ray diffraction. Polymerization of racemic lactide, with addition of alcohol, yielded PLA with narrow polydispersities but low molecular weights.     

C,O-dialkylation of Meldrum's acid: synthesis and reactivity of 1,3,7,7-tetramethyl-4H,10H-6,8,9-trioxa-2-thiabenz[f]azulen-5-one

Reaction of Meldrum's acid with 3,4-bis(chloromethyl)-2,5-dimethylthiophene (1) or 3,4-bis(bromomethyl)-2,5-dimethylthiophene (2) produces the kinetically favored C,O-dialkylation product, 1,3,7,7-tetramethyl-4H,10H-6,8,9-trioxa-2-thiabenz[f]azulen-5-one (4). Recrystallization of 4 from refluxing methanol results in the methanolysis product 5-(4-methoxymethyl-2,5-dimethylthiophen-3-ylmethyl)-2,2-dimethyl[1,3]dioxane-4,6-dione (5). Attempts to isomerize 4 to the thermodynamically favored C,C-dialkylation product, 1,3-dimethyl-5,6-dihydro-4H-cyclopenta[c]thiophene(2-spiro-5)2,2-dimethyl-4,6-dione (8), result in the formation of 1,3-dimethyl-7,8-dihydro-4H-thieno[3,4-c]oxepin-6-one (6). The transformation occurs via a retro-Diels-Alder elimination of acetone followed by hydrolysis and decarboxylation of the resulting ketene. The ketene is trapped by tert-butyl alcohol, furnishing 1,3-dimethyl-6-oxo-7,8-dihydro-4H,6H-thieno[3,4-c]oxepine-7-carboxylic acid tert-butyl ester (7). All compounds are characterized spectroscopically as well as by X-ray crystallography of products 4-7.     

Manganese(III)-mediated intermolecular cyclization reactions of alkenes and active methylene compounds

The reactions of 1,1-diphenylethene, 1,1-bis(4-chlorophenyl)ethene, 1,1-bis(4-methylphenyl)ethene, and 1,1-bis(4-methoxyphenyl)ethene with 3,5-diacetyl-2,6-heptanedione in the presence of manganese(III) acetate in acetic acid at 80° yielded 4,6-diacetyl-8,8-diaryl-1,3-dimethyl-2,9-dioxabicyclo[4.3.0]non-3-enes (41-48%), 5-acetyl-2,2-diaryl-6-methyl-2,3-dihydrobenzo[b]furans (20–21%), 3-acetyl-5,5-diaryl-2-methyl-4,5-dihydrofurans (5–10%), and benzophenones (3–7%). Similarly, the reactions of 1,1-diarylethenes with dimethyl 2,4-diacetyl-1,5-pentanedioate or diethyl 2,4-diacetyl-1,5-pentanedioate gave the corresponding 4,6-bis(alkoxycarbonyl)-8,8-diaryl-1,3-dimethyl-2,9-dioxabicyclo[4.3.0]non-3-enes in moderate yields.     

The reductive dimerization of some 1,3-dienes and of 1,3,5-cycloheptatriene in the presence of trimethylchlorosilane: a DFT investigation

Treatment of 1,3-dienes and 1,3,5-cycloheptatriene by chlorotrimethylsilane in the presence of wire of lithium led mainly to reductive dimerization with formation of bis(allylsilane) derivatives. Bis-silyl compounds obtained: from 1,3-butadiene, 1,8-bis(trimethylsilyl)-2,6-octadiene (70%); from isoprene, (Z,Z)-2,7-dimethyl-1,8-bis(trimethylsilyl)-2,6-octadiene (44%) and 2,6-dimethyl-1,8-bis(trimethylsilyl)-2,6-octadiene (19%); from butadiene-isoprene mixture (1:1), 3-methyl-1,8-bis(trimethylsilyl)-2,6-octadiene (55%); from 2,3-dimethylbutadiene, (E,E)-2,3,6,7-tetramethyl-1,8-bis(trimethylsilyl)-2,6-octadiene (36%), from 1,3-cyclohexadiene, 4,4′-bis(trimethylsilyl)-bicyclohexyl-2,2′-diene (48%); from 1,3,5-cycloheptatriene, 1,1′-bi[(S^∗,S^∗)-6-(trimethylsilyl)cyclohepta-2,4-dien-1-yl] (53%). The structure of the various intermediates (radical anion, dianion, silylated radical, silylated anion) has been established by calculations at the B3LYP/6-311++G(d,p) level of theory with zero-point energy correction. These results are in accordance with a pathway including the formation of a radical anion, its silylation furnishing to a γ-silylated allylic radical followed by a dimerization reaction in the head to head manner.     

Molecular design of lipophilic disalicylic acid compounds with varying spacers for selective lead(II) extraction

Lipophilic disalicylic acids 5,5'-decyl-2,2'-[1,2-ethanediylbis(oxy)]bisbenzoic acid (1), 5,5'-decyl-2,2'-[1,3-propanediylbis(oxy)]bisbenzoic acid (2), 5,5'-decyl-2,2'-[oxybis(1,2-ethanediyl-oxy)]bisbenzoic acid (3), 3,5-bis[2'-(2'-carboxyphenoxy)ethyl]-4-oxahexacyclo-[5.4.1.0(2,6).0(3,10).0(5,9).0(8,11)]dodecane (4), and 1,3-bis[2'-(2'-carboxyphenoxy)ethyl]adamantane (5) are evaluated as selective Pb(II) extractants. The solvent extraction of Pb(II) and of Cu(II) from buffered aqueous solutions of varying pH into chloroform by ligands 1-5 is examined in relation to the molecular structure of the dicarboxylic acid extractant. Ligand 1, with an ethylene spacer between two lipophilic salicylic acid units, exhibits excellent extraction selectivity for Pb(II) over Cu(II). Lengthening the spacer in ligands 2 and 3 diminishes both the extraction efficiency and selectivity. Ligands 4 and 5, with rigid spacer units, show significant reductions in both Pb(II) and Cu(II) extraction. Slope analysis reveals that ligand 1 reacts in a 2:1 stoichiometry with Pb(II) in extraction, which differs from the 1:1 stoichiometries for 2 and 3. The differences in the half extraction pH (DeltapH(1/2)) values for Pb(II) and Cu(II) extraction are 1.29, 0.49, and 0.48 for 1-3, respectively.     

Investigation of reactions of the organozinc reagents prepared from zinc and dialkyl dibromomalonates with the derivatives of 2-arylmethyleneindan-1,3-dione and 5-arylmethylene-2,2-dimethyl-1,3-dioxane-4,6-dione

Organozinc compounds prepared from dialkyl dibromomalonates and zinc react with 2-arylmethyl-eneindan-4,6-diones, 5-arylmethylene-2,2-dimethyl-1,3-dioxane-4,6-diones, as well as with 2-[4-(1,3-dioxoindan-2-ylidenemethyl)phenyl]methyleneindan-1,3-dione and 5-[4-(2,2-dimethyl-4,6-dioxo-1,3-dioxane-2-ylidenemethyl)phenyl]methylene-2,2-dimethyl-1,3-dioxane-4,6-diones to form dialkyl 3-aryl-1′3′-dioxaspiro(cyclopropane-2,2′-indan)-1,1-dicarboxylates, dimethyl 3-aryl-6,6-dimethyl-5,7-dioxa-4,8-dioxaspiro[2,5]octan-2,2-dicarboxylates, dialkyl 2-{4-[3,3-bis (alkoxycarbonyl)-1′,3′-dioxaspiro(cyclopropane-2,2′-indan)-1-yl]phenyl}-1′,3′-dioxaspiro[cyclopropane-2,2′-indan]-1,1-dicarboxylates, and dialkyl 2-{4-[2,2-bis(alkoxycarbonyl)-6,6′-dimethyl-4,8-dioxo-5,7-dioxaspiro[2,5]oct-1-yl]phenyl}-6,6-dimethyl-4,8-dioxo-5,7-dioxaspiro[2,5]octan-1,1-dicarboxylate respectively.     

Synthesis of glutarimide antibiotics and their analogs through 1,3-cycloaddition of 3-glutarimidylacetonitrile oxide to 2-cyclohexenones

A mixture of 4,4-dimethyl-9-(3-methylglutarlmidyl)-2-oxo-7-oxa-8-azabicyclo[4.3.0] non-8-ene and 3-(3-methylglutarimidyl)-6,6-dimethyl-4-oxo-4,5,6,7-tetrahydrobenz-[d]isoxazole was obtained by in situ 1,3-dipolar cycloaddition of 3-glutarimidyl-acetonitrile oxide to 5,5-dimethylcyclohex-2-en-1-one. Reductive cleavage of these compounds by catalytic hydrogenation over Pd catalysts gives 3-[2-amino-2,2-(4,4-dimethyl-2-oxocyclohexylene)ethyl]glutarimide and the known 3-[2-amino-2,2-(4,4-dimethyl-2,6-dioxocyclohexylene)ethyl]glutarimide, respectively, in quantitative yield. Hydrolysis of the latter leads to 3-[2-oxo-2-(4,4-dimethyl-2,6-dioxocyclo-hexyl)ethyl]glutarimide. The ketones obtained are analogs of glutarimide antibiotics and polyfunctional intermediates in their synthesis.See [1] for a preliminary communication.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 230–234, February, 1979.     

3,3-Dimethyl-2,3,5,6-tetrahydroimidazo[2,1-b][1,3,4]thiazasilole and Its Derivatives with Five-Coordinate Silicon Atom

Previously unknown 3,3-dimethyl-2,3,5,6-tetrahydroimidazo[2,1-b][1,3,4]thiazasilole and its zwitterionic derivatives containing five-coordinate silicon atom, namely 7-substituted 3,3-dimethyl-2,3,5,6-tetrahydroimidazo[2,1-b][1,3,4]thiazasilol-4-ium chlorides, have been synthesized by reaction of 1,3-bis(trimethylsilyl)tetrahydroimidazole-2-thione with chloro(chloromethyl)dimethylsilane and subsequent transformations of the products.     

新型树形化合物1,3,5-三-[7-(7-甲基-2,2-二-(2,2-二羟甲基-3-羟基丙氧基羰基)-6,8-二氧杂螺[3.5]-壬基)]苯的合成

以丙酮和甲酸乙酯为原料, 在醇钠的作用下合成了1,3,5-三乙酰基苯(1). 1与二溴新戊二醇在酸的作用下发生缩酮化反应, 制成1,3,5-三-(1-甲基-2,6-二氧杂-4,4-二溴甲基环己基)苯(2). 2与5,5-二甲基-4,6-二氧杂-1,3-环己二酮在乙醇钠的作用下合成了1,3,5-三-[7-(7-甲基-2,2-二-乙氧羰基-6,8-二氧杂螺[3.5]-壬基)]苯(3). 将3在氯仿中与季戊四醇进行酯交换反应得到产物1,3,5-三-[7-(7-甲基-2,2-二-(2,2-二羟甲基-3-羟基丙氧基羰基)-6,8-二氧杂螺[3.5]-壬基)]苯(4). 收率为47.7%. 标题化合物及中间产物使用IR, ¹H NMR和MS或元素分析进行了表征.     

Acyl- und Alkylidenphosphane. XII [1]. Synthese und Eigenschaften des 2,2-Dimethylpropionylphosphans und einiger Derivate

Acyl and alkylidene phosphines. XII. Syntheses and properties of 2,2-dimethylpropionylphosphine and of some derivatives At ?25°C bis(trimethylsilyl)phosphine 1b and 2,2-dimethylpropionyl chloride form (2,2-dimethylpropionyl)trimethylsilylphosphine 2b . As this compound is thermally more stable than similar acyltrimethylsilylphosphines, it might be treated at ?55°C with methyllithium to form the correspondig lithium phosphide 2d ; after the addition of chlorotrimethylsilane [2,2-dimethyl-1-(trimethylsiloxy)propylidene]-trimethylsilylphosphine 3c is obtained. At +20°C 2b rearranges to the E and Z isomer of [2,2-dimethyl-1-(trimethylsiloxy)propylidene]phosphine 3b . The NMR data of E- 3b and Z- 3b differ mostly in the coupling constants. Kept in the diffuse daylight for several days 3b dimerizes to form 2,4-di(tert.butyl)-2,4-bis(trimethylsiloxy)-1,3-diphosphetane 10 . In solution 10 is unstable and decomposes again to a mixture of the E und Z isomer of 3b . Reacting 3b or 3c with alcoholes all trimethylsilyl groups are replaced by hydrogen atoms and unstable 2,2-dimethylpropionylphosphane 4b is formed. Lithium(2,2-dimethylpropionyl)phosphide 4d , synthesized at ?60°C from 4b and methyllithium, crystallizes with one molecule 1,2-dimethoxyethane per formula unit and is dimeric in benzene. As shown by the NMR data 4d has the structure of an alkylidene-phosphine with the lithium atom bound to oxygen. At ?50°C 4d and chlorotrimethylsilane react to form 3b .     

Synthesis of 5-Aryl-2,2-dimethyl-4-oxaspiro[5,5]undecane-1,3-diones by Reformatsky Reaction

Alkyl 3-(1-bromocyclohexyl)-2,2-dimethyl-3-oxopropanoates react with zinc and aromatic aldehydes to yield 5-aryl-2,2-dimethyl-4-oxaspiro[5,5]undecane-1,3-diones.     

二（2,6-二甲基-4-甲氧基）苯基卡宾的产生和反应

为了考察卡宾稳定性的电子效应,合成了对位具有强推电性甲氧基的二（2, 6-二甲基-4-甲氧基）苯基重氮甲烷(1c),通过光分解而产生了二（2,6-二甲基- 4-甲氧基）苯基卡宾(2c)。分别用电子顺磁共振（EPR）光谱,紫外可见(UV/vis) 光谱及激光闪光光分解法对二（2,6-二甲基-4-甲氧基）苯基卡宾(2c)的产生和衰 减过程进行了详细的观察。由于甲氧基的强推电子作用使二苯基卡宾的稳定性大大 降低,其二次动力学衰减速度常数为130s~(-1),是对位非取代二苯基卡宾(2b) (14s~(-1))的约9倍,且室温苯溶液中的寿命为20ms,仅为2b(180ms)的1/9。且通过 产物分析对二（2,6-二甲基-4-甲氧基）苯基卡宾(2c)的反应及甲氧基的取代基效 应进行了详细探讨。     

Heterocyclization of 1,1-dicyano-2-(trifluoromethyl)ethylenes with 1,3,3-trimethyl-3,4-dihydroisoquinoline and its derivatives

1,3,3-Trimethyl-3,4-dihydroisoquinolines react with 1,1-dicyano-2,2-bis(trifluoromethyl)ethylene to give 4-amino-6,6-dimethyl-2,2-bis(trifluoromethyl)-3-cyano-6,7-dihydro-2H-benzo[a]quinolizines. The reaction of 3,3-dimethyl-1-cyanomethylidene-1,2,3,4-tetrahydroisoquinoline and the methyl ester of 3,3-dicyano-2-(trifluoromethyl)acrylic acid leads to 5,5-dimethyl-3-oxo-2-(trifluoromethyl)-2-(dicyanomethyl)-2,3,5,6-tetrahydropyrrolo[2,1-a]isoquinoline.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1888–1892, August, 1992.     

Bis[bis-(4-alkoxyphenyl)amino] derivatives of dithienylethene, bithiophene, dithienothiophene and dithienopyrrole: palladium-catalysed synthesis and highly delocalised radical cations

Five diamines with thiophene-based bridges--(E)-1,2-bis{5-[bis(4-butoxyphenyl)amino]-2-thienyl}ethylene (1), 5,5'-bis[bis(4-methoxyphenyl)amino]-2,2'-bithiophene (2), 2,6-bis[bis(4-butoxyphenyl)amino]dithieno[3,2-b:2',3'-d]thiophene (3), N-(4-tert-butylphenyl)-2,6-bis[bis(4-methoxyphenyl)amino]dithieno[3,2-b:2',3'-d]pyrrole (4 a) and N-tert-butyl-2,6-bis[bis(4-methoxyphenyl)amino]dithieno[3,2-b:2',3'-d]pyrrole (4 b)--have been synthesised. The syntheses make use of the palladium(0)-catalysed coupling of brominated thiophene species with diarylamines, in some cases accelerated by microwave irradiation. The molecules all undergo facile oxidation, 4 b being the most readily oxidised at about -0.4 V versus ferrocenium/ferrocene, and solutions of the corresponding radical cations were generated by addition of tris(4-bromophenyl)aminium hexachloroantimonate to the neutral species. The near-IR spectra of the radical cations show absorptions characteristic of symmetrical delocalised species (that is, class III mixed-valence species); analysis of these absorptions in the framework of Hush theory indicates strong coupling between the two amine redox centres, stronger than that observed in species with phenylene-based bridging groups of comparable length. The strong coupling can be attributed to high-lying orbitals of the thiophene-based bridging units. ESR spectroscopy indicates that the coupling constant to the amino nitrogen atoms is somewhat reduced relative to that in a stilbene-bridged analogue. The neutral species and the corresponding radical cations have been studied with the aid of density functional theory and time-dependent density functional theory. The DFT-calculated ESR parameters are in good agreement with experiment, while calculated spin densities suggest increased bridge character to the oxidation in these species relative to that in comparable species with phenylene-based bridges.     

Synthesis of dithieno[2,3-b:4',3'-d]siloles and their selective bromination

The efficient synthesis of novel unsymmetrical dithienosiloles, 7,7-dimethyl-4,6-di(trimethylsilyl)-dithieno[2,3-b:4',3'-d]silole (1) and 7,7-dimethyl-2,4,6-tri(trimethylsilyl)-dithieno[2,3-b:4',3'-d]silole (2) has been developed by intramolecular silole formation with 4,4'-dibromo-2,2',5,5'-tetrakis(trimethylsilyl)-[3,3']bithienyl (3) as the starting material in the presence of t-BuLi. Upon treatment with N-bromosuccinimide (NBS) under controlled conditions, dithieno[2,3-b:4',3'-d]silole was selectively brominated to produce mono-, di-, and tribrominated dithieno[2,3-b:4',3'-d]siloles in good yields. The crystal structures of the title compounds are described.     

Decoupling optical and potentiometric band gaps in pi-conjugated materials

Syntheses, optical spectroscopy, potentiometric studies, and electronic structural calculations are reported for two classes of conjugated (porphinato)metal oligomers that feature a meso-to-meso ethyne-bridged linkage topology. One set of these systems, bis[(5,5'-10,20-bis[3,5-bis(3,3-dimethyl-1-butyloxy)phenyl]porphinato)zinc(II)]ethyne (DD), 5,15-bis[[5'-10',20'-bis[3,5-di(3,3-dimethyl-1-butyloxy)phenyl]porphinato)zinc(II)]ethynyl]-10,20-bis[3,5-di(9-methoxy-1,4,7-trioxanonyl)phenyl]porphinato)zinc(II) (DDD), and 5,15-bis[[15' '-(5'-10',20'-bis[3,5-bis(3,3-dimethyl-1-butyloxy)phenyl]porphinato)zinc(II)]-[(5' '-10' ',20' '-bis[3,5-di(9-methoxy-1,4,7-trioxanonyl)phenyl]porphinato)zinc(II)]ethyne]ethynyl]-10,20-bis[3,5-di(9-methoxy-1,4,7-trioxanonyl)phenyl]porphinato)zinc(II) (DDDDD), constitute highly soluble analogues of previously studied examples of this structural motif having simple 10,20-diaryl substituents, while a corresponding set of conjugated oligomers, [(5-10,20-bis[3,5-bis(3,3-dimethyl-1-butyloxy)phenyl]porphinato)zinc(II)]-[(5'-15'-ethynyl-10',20'-bis[10,20-bis(heptafluoropropyl)porphinato)zinc(II)]ethyne (DA), 5,15-bis[[5'-10',20'-bis[3,5-di(3,3-dimethyl-1-butyloxy)phenyl]porphinato)zinc(II)]ethynyl]-10,20-bis(heptafluoropropyl)porphinato]zinc(II) (DAD), and 5,15-bis[[15' '-(5'-10',20'-bis[3,5-bis(3,3-dimethyl-1-butyloxy)phenyl]porphinato)zinc(II)]-[(5' '-(10' ',20' '-bis(heptafluoropropyl)porphinato)zinc(II)]ethyne]ethynyl]-10,20-bis[3,5-di(9-methoxy-1,4,7-trioxanonyl)phenyl]porphinato)zinc(II) (DADAD), features alternating electron-rich and electron-poor (porphinato)zinc(II) units. Electrooptic and computational data for these species demonstrate that it is possible to engineer conjugated oligomeric structures that possess highly delocalized singlet (S1) excited states yet manifest apparent one-electron oxidation and reduction potentials (E1/20/+ and E1/2-/0 values) that are essentially invariant with respect to those elucidated for their constituent monomeric precursors.     

Synthesis of new imines and amines containing organosilicon groups

The Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyl lithium, (Me₃Si)₃CLi, in THF at 0 °C gives 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde (1) and 4,4-bis[2,2-bis(trimethylsilyl)ethenyl]benzene (2). The new aldehyde (1) reacts with variety of amines in ethanol to afford the corresponding imines (3) containing vinylbis(trimethylsilyl) group. The newly synthesized imines (3) can be completely converted into amines containing vinylbis(trimethylsilyl) group with an excess amount of NaBH₄. In the case of N-[4-(2,2-bis(trimethylsilyl)ethenyl)benzyl]-2,6-dimethylaniline LiAlH₄ was used as a reducing agent in THF.     

Titanium-mediated addition of diallylsilanes to oxalyl chloride: formation of a diquinane

The titanium tetrachloride mediated reaction of the cis,cis-2,6-dimethyl-1,8-bis(trimethylsilyl)-2,6-octadiene with oxalyl chloride yielded 1-hydroxy-4-methyl-8-(1-propen-2-yl)bicyclo[3.3.0]oct-3-en-2-one of which the structure was confirmed by X-ray crystallographic analysis.     

Formation of substituted 6-hydroxy-5-oxo-5,6-dihydrobenzo[c][2,7]naphthyridine upon photochemical transformation of nifedipine

Long-term exposure of nifedipine to daylight in ethanol gives 2,2"-bis[3,5-bis(methoxycarbonyl)-2,6-dimethylpyridin-4-yl]azoxybenzene and 6-hydroxy-1-methoxycarbonyl-2,4-dimethyl-5-oxo-5,6-dihydrobenzo[c][2,7]naphthyridine as the major products.