Synthesis of diazeniumdiolates from the reactions of nitric oxide with enolates

[reaction: see text] Reactions of nitric oxide with enolates derived from aliphatic methyl ketones containing alpha-methylene or alpha-methine groups and with enolates derived from alpha,alpha'-dimethylene or alpha,alpha'-dimethine ketones yield mono- or bis(diazeniumdiolate) products. Diazeniumdiolation occurs in the following order: alpha-methine > alpha-methylene > alpha-methyl. The amount of the base used alters the extent of diazeniumdiolation and the course of the reaction. Mono- and bis(diazeniumdiolate)-substituted methyl ketones are cleaved in the presence of excess base before and after the subsequent diazeniumdiolation of the alpha-methyl group. Similar to the trihalogenated methyl groups in the base-assisted halogenation reactions of methyl ketones, the bis(diazeniumdiolate)-substituted alpha-methylene and alpha-methyl groups act as leaving groups in the presence of excess base. The reaction of nitric oxide with a (approximately 20:80, cis/trans) mixture of 2,6-cyclohexananone yields the cis and trans isomers of 2,6-dimethylcyclohexanone-2,6-bis(diazeniumdiolate) in 12.9% and 57.6% yield. Single-crystal X-ray diffraction data determined for potassium cis-2,6-dimethylcyclohexanone-2,6-bis(diazeniumdiolate), cis-14b, reveal that the N(2)O(2-) substituent is planar with considerable delocalization of a double bond over the anionic four-atom group. Except for one of the diazeniumdiolate products, namely, potassium propanoate 2,2-bis(diazeniumdiolate), 8b, all are stable in neutral and basic aqueous media. Compound 8b slowly decomposes in neutral aqueous solution releasing nitrous oxide and nitric oxide gases but is stable in basic aqueous media. Differential scanning calorimetry data measured for the diazeniumdiolate products indicate that they decompose exothermally with most of them undergoing explosive decomposition at moderately high temperatures (181-274 degrees C).     

An improved method for 14C-labelling of farnesylacetic acid and its geranyl ester

Farnesylacetic acid was efficiently labelled with 14C at the 5-position and gefarnate, a potent ulcer inhibitor, was prepared from it in radioactive form for use in metabolic studies. Condensation of [carbonyl-14C]acetyl chloride (5) with t-butyl 2-ethoxymagnesiomalonate (6) followed by acid-catalyzed deprotection and decarboxylation gave ethyl 3-oxo[3-14C]butanoate (8). Alkylation of the keto ester (8) with geranyl bromide (9) afforded the unsaturated keto ester (10), which was hydrolyzed and decarboxylated to give geranyl[2-14C]acetone (11). Grignard reaction of 11 with cyclopropylmagnesium bromide followed by treatment with hydrobromic acid yielded [4-14C]homofarnesyl bromide (13). Cyanation of 13 with potassium cyanide and subsequent hydrolysis gave [5-14C]farnesylacetic acid (1) in 6.1% yield from barium [14C]carbonate (3). Chlorination of 1 followed by esterification with geraniol afforded [5-14C]gefarnate (2) in 88% yield.     

Stereospecific substitution of enantiomerically pure 1-(2-pyridinyl)ethyl methanesulfonate with beta-dicarbony compounds

The alkylation of the sodium salt of the malonic acid diester with (R)-1-(2-pyridinyl)ethyl methanesulfonate (2) gave the dimethyl (R)-[1-(2-pyridinyl)ethyl]malonate (3a), stereospecifically. The alkylation reaction of methyl acetoacetate gave the methyl (2'S,2R/2S)-3-oxo-2-[1-(2-pyridinyl)ethyl]butanoate (3d) along with the methyl (S)-3-[1-(2-pyridinyl)ethoxy]-2-butenoate (4d). The acid hydrolysis and decarboxylation of 3d under acidic conditions gave (R)-4-(2-pyridinyl)pentan-2-one (6), and the alkylation of methyl (R)-[1-(2-pyridinyl)ethyl]acetoacetate with benzyl bromide gave a mixture of C-benzylated and O-benzylated products 7 and 8.     

Magnetic ordering in the rare earth molecule-based magnets,Ln(TCNE)(3) (Ln = Gd,Dy; TCNE = tetracyanoethylene)

The reaction of LnI(3) x xMeCN (Ln = Gd, Dy) and TCNE (tetracyanoethylene) in acetonitrile forms Ln(2)[C(4)(CN)(8)](3) x xMeCN. These paramagnetic light-colored solids contain the S = 0 octacyanobutandiide dianion, [C(4)(CN)(8)](2-), which upon desolvation of these products forms dark green Ln(TCNE)(3). In these compounds the central C[bond]C sigma bond in [C(4)(CN)(8)](2-) is broken, re-forming S = 1/2 [TCNE]*(-). as evidenced by the color change and the infrared spectra. Ln(TCNE)(3) exhibit coupling between Ln(3+) and [TCNE]*(-) and magnetically order as ferrimagnets at 8.5 (Dy) and 3.5 (Gd) K.     

Synthesis and antimicrobial activity of some derivatives of (7-hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid hydrazide

(7-Hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid hydrazide (2) was prepared from (7-hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid ethyl ester (1) and 100% hydrazine hydrate. Compound 2, is the key intermediate for the synthesis of several series of new compounds such as Schiff's bases 3a-l, formic acid N'-[2-(7-hydroxy-2-oxo-2H- chromen-4-yl)acetyl] hydrazide (4), acetic acid N'-[2-(7-hydroxy-2-oxo-2H-chromen-4- yl)-acetyl] hydrazide (5), (7-hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid N'-[2-(4- hydroxy-2-oxo-2H-chromen-3-yl)-2-oxoethyl] hydrazide (6), 4-phenyl-1-(7-hydroxy-2- oxo-2H-chromen- 4-acetyl) thiosemicarbazide (7), ethyl 3-{2-[2-(7-hydroxy-2-oxo-2H- chromen-4-yl)-acetyl]hydrazono}butanoate (8), (7-hydroxy-2-oxo-2H-chromen-4-yl)- acetic acid N'-[(4-trifluoromethylphenylimino)methyl] hydrazide (9) and (7-hydroxy-2- oxo-2H-chromen-4-yl)acetic acid N'-[(2,3,4-trifluorophenylimino)-methyl] hydrazide (10). Cyclo- condensation of compound 2 with pentane-2,4-dione gave 4-[2-(3,5- dimethyl-1H-pyrazol-1-yl)-2-oxoethyl]-7-hydroxy-2H-chromen-2-one (11), while with carbon disulfide it afforded 7-hydroxy-4-[(5-mercapto-1,3,4-oxadiazol-2-yl)methyl]-2H- chromen-2-one (12) and with potassium isothiocyanate it gave 7-hydroxy-4-[(5- mercapto-4H-1,2,4-triazol-3-yl)methyl]-2H-chromen-2-one (14). Compound 7 was cyclized to afford 2-(7-hydroxy-2-oxo-2H-chromen-4-yl)-N -(4-oxo-2-phenylimino- thiazolidin-3-yl) acetamide (15).     

A novel acyclic addition of ketenes to oxazoles/oxazolines

The addition of n-butyryl chloride (1) to 5-phenyloxazole (6) or 4,5-dihydro-5-methyl-4-[(4′-methylphenyl)-sulfonyl]oxazole (8) in the presence of triethylamine lead to 1-(5′-phenyloxazol-2′-yl)-1-buten-1-yl butanoate (7) and 1-(5′-methyl-4′-[4″-methylphenylsulfonyl]4′,5′-dihydrooxazol-2′-yl)-1-buten-1-yl butanoate (9) , respectively.     

Cluster synthesis via ligand-arrested solid growth: triethylphosphine-capped fragments of binary metal chalcogenides

A new and potentially highly generalizable technique for synthesizing molecular fragments of binary solids is demonstrated through application to selected transition metal chalcogenides. Employing a metal atom reactor, the solids are evaporated with a tungsten heating boat, and the resulting vapor is co-condensed with triethylphosphine. Major cluster products identified from a survey of first-row transition metal sulfides include the known species Cr6S8(PEt3)6, Co6S8(PEt3)6, and Cu12S6(PEt3)8, as well as the unprecedented species Fe4S4(PBun3)4, Ni4S4(PEt3)8, and Cu6S4(PEt3)4. Reactions utilizing Cu2Se resulted in the much larger clusters Cu26Se13(PEt3)14 and Cu70Se35(PEt3)21. The core of the former has a Th-symmetry structure featuring a body-centered icosahedron of Se2- anions, while the latter adopts a triangular structure based on three hexagonal closest packed layers of Se2- anions. In both cases, the Cu+ cations occupy distorted tetrahedral or trigonal planar sites similar to those encountered in Cu2Se; however, emergence of the face-centered cubic anion lattice of the bulk solid is not yet apparent at these cluster sizes.     

Synthesis and Crystal Structure of Ethyl 2-(6-(1,3-Dioxo-4,5,6,7-tetrahydro-1H-isoindol-2(3H)-yl)-7-fluoro-3-oxo-2H-benzo[b][1,4]oxazin-4(3H)-yl) Butanoate

The title compound ethyl 2-(6-(1,3-dioxo-4,5,6,7-tetrahydro-1H-isoindol-2(3H)-yl)-7-fluoro-3-oxo-2H-benzo[b][1,4]oxazin-4(3H)-yl) butanoate 3 was synthesized by the reaction of ethyl 2-(6-amino-7-fluoro-3-oxo-2H-benzo[b][1,4]oxazin-4(3H)-yl) butanoate with 4,5,6,7-tetraydrophthalic anhydride,and its structure was determined by X-ray single-crystal diffraction.The crystal belongs to the monoclinic system,space group P21/n with a = 9.3469(2),b = 16.7715(5),c = 13.7153(4) ,β = 104.9680(10)°,μ = 0.107 mm-1,Mr = 430.42,V = 2077.08(10) 3,Z = 4,Dc = 1.376 g/cm3,F(000) = 904,T = 296(2) K,R = 0.0508 and wR = 0.1478.     

Synthesis, structure, reactivity, and thermal isomerization of boron-substituted 13-vertex cobaltacarboranes (eta5-Cp)Co(eta6-R2C2B10Me8H2) (R = H, Et)

Reduction of boron-substituted carboranes o-R2C2B10Me8H2 (R = H, Et), thermal isomerization, and nucleophilic reaction of the resultant 13-vertex cobaltacarboranes were studied. Reaction of o-C2B10Me8H4 (1) with excess potassium metal in tetrahydrofuran (THF) gave, after recrystallization from a THF solution of 18-crown-6 ether, [[K(18-crown-6)(THF)2][K(18-crown-6)]][[4-(18-crown-6)-2,3,5,8,9,11,12,13-Me8-4,1,6-KC2B10H4]2] (2) in 78% yield. Interaction of 1 with excess sodium or potassium metal in THF, followed by treatment with CoCl2/CpNa and then aerobatic oxidation, afforded two boron-substituted 13-vertex cobaltacarboranes, 4-Cp-2,3,5,8,9,11,12,13-Me8-4,1,6-CoC2B10Me8H4 (3) and 4-Cp-2,3,5,9,10,11,12,13-Me8-4,1,6-CoC2B10Me8H4 (4), in 15% and 8% yield, respectively. Subsequently, thermal isomerization of 3 and 4 yielded another two new isomers, 4-Cp-2,3,5,6,8,11,12,13-Me8-4,1,9-CoC2B10Me8H4 (5) and 4-Cp-2,3,5,6,7,11,12,13-Me8-4,1,9-CoC2B10Me8H4 (6). Treatment of 3 or 4 with strong bases such as nBuLi and MeLi generated unexpected nucleophilic substitution products 4-nBuCp-2,3,5,8,9,11,12,13-Me8-4,1,6-CoC2B10Me8H4 (7), 4-nBuCp-2,3,5,9,10,11,12,13-Me8-4,1,6-CoC2B10Me8H4 (8a), and 4-MeCp-2,3,5,9,10,11,12,13-Me8-4,1,6-CoC2B10Me8H4 (8b) in good yields. Under the same reaction conditions, however, only one 13-vertex cobaltacarborane, 4-Cp-1,9-Et2-2,5,6,7,8,11,12,13-Me8-4,1,9-CoC2B10Me8H4 (10), was isolated when o-Et2C2B10Me8H2 (9) was used as the starting material. Complex 10 is a thermodynamically stable product and has a substitution pattern different from that of 3-6. These results show that the substituents on either the cage carbon or boron atoms have an important effect on the formation and thermal stability of the 13-vertex metallacarboranes. The formation of these complexes can be rationalized by the diamond-square-diamond mechanism.     

Reaction of nitric oxide at the beta-carbon of enamines. A new method of preparing compounds containing the diazeniumdiolate functional group

The reaction of nitric oxide (NO) with enamines has been investigated. Unlike previously reported reactions of NO as a free radical with alkenes, the electrophilic addition of NO to the beta-carbon of enamines results in the formation of compounds containing the diazeniumdiolate functional group (-[N(O)NO](-)). This reaction between NO and enamines has been shown to be quite general and a variety of enamine-derived diazeniumdiolates have been isolated and characterized. While enamines derived from aldehydes and ketones whose structures allow for sequential multiple electrophilic additions tended to undergo overreaction leading to unstable products, it has been shown that this complication may be overcome by suitable choice of reaction solvent. The products obtained may exist as zwitterionic iminium salts or as neutral species depending upon the structure of the parent enamine. The diazeniumdiolate derived from 1-(N-morpholino)cyclohexene is unique among the new compounds in that it spontaneously releases NO upon dissolution in buffered aqueous solution at pH 7.4 and 37 degrees C. While the total quantity of NO released by this material (ca. 7% of the theoretical 2 moles) is apparently limited by a competing reaction in which it hydrolyzes to an alpha-diazeniumdiolated carbonyl compound and the parent amine, this feature may prove to be of great value in the development of multiaction pharmaceuticals based upon this new type of NO-releasing compound. Reports of enzymatic (oxidative) release of NO from previously known carbon-bound diazeniumdiolates also suggest that analogues of these compounds may be useful as pharmaceutical agents. This new method of introducing the relatively rarely studied diazeniumdiolate functional group into organic compounds should lead to further research into its chemical and biological properties.     

O2-(N-hydroxy(methoxy)-2-ethanesulfonamido) protected diazen-1-ium-1,2-diolates: nitric oxide release via a base-induced β-elimination cleavage

O(2)-(Ethanesulfohydroxamic acid) and O(2)-(N-methoxy-2-ethanesulfonylamido) diazen-1-ium-1,2-diolates (4-7), a novel type of O(2)-(protected) diazeniumdiolate, were synthesized using a key thioacetate oxidation reaction. Nitric oxide release studies showed that O(2)-(N-methoxy-2-ethanesulfonylamido) diazeniumdiolates 5 and 7 released NO in a nonphysiological alkaline buffer, in the presence of bases such as the basic natural amino acids Arg and His, or the non-nucleophilic organic base DBU in PBS at pH 7.4, via a β-elimination cleavage reaction.     

Tris(pyrazolyl)borate carbosilane dendrimers and metallodendrimers

A modified tris(pyrazolylborate) ligand has been prepared in two steps. First, reaction of triisopropylborate with allylmagnesium bromide and further treatment with benzoyl chloride gave CH(2) = CHCH(2)B(O(i)Pr), which was then reacted with potassium pyrazolate and pyrazole to give the compound K[CH(2) = CHCH(2)Bpz(3)]. The new allyl-containing scorpionate anion of acts as a bi- or tri-dentate ligand, as shown by the mononuclear complexes [CH(2) = CHCH(2)Bpz(3)M(LL)] (M = Rh, LL = nbd, ; LL = tfb, ; LL = (CO)(PPh(3)), ; M = Ir, LL = cod, ), obtained from reactions of the chlorido-bridged dinuclear complexes [{M(mu-Cl)(LL)}(2)] with 2. Furthermore, the borate represents a key material to achieve the attachment of tris(pyrazolyl)borate groups to the peripheries of carbosilane dendrimers. Thus, the platinum-catalyzed hydrosilylation reactions of compound with the dendritic cores Si[(CH(2))(3)SiMe(2)H](4) (G(0)-(SiH)(4)), (G(1)-(SiH)(8)), and (G(2)-(SiH)(16)) gave the corresponding borate-containing dendrimers Si[(CH(2))(3)SiMe(2)(CH(2))(3)B(O(i)Pr)(2)](4) (G(0)-B(4)), Si[(CH(2))(3)SiMe{(CH(2))(3)SiMe(2)(CH(2))(3)B(O(i)Pr)(2)}(2)](4) (G(1)-B(8)), and Si[(CH(2))(3)SiMe{(CH(2))(3)SiMe[(CH(2))(3)SiMe(2)(CH(2))(3)B(O(i)Pr)(2)](2)}(2)](4) (G(2)-B(16)) selectively in the anti-Markovnikov direction. Further reactions of G(0)-B(4), G(1)-B(8) and G(2)-B(16) with potassium pyrazolate and pyrazole rendered the corresponding polyanionic dendrimers K(4)[Si{(CH(2))(3)SiMe(2)(CH(2))(3)Bpz(3)}(4)] (G(0)-(Bpz(3))(4)), G(1)-(Bpz(3))(8), and G(2)-(Bpz(3))(16), respectively, which contain 4, 8, and 16 tris(pyrazolyl)borate groups symmetrically located around the dendritic peripheries. These unusual polyanionic dendrimers are excellent scaffolds to support metal centres, as shown by the reactions of G(0)-(Bpz(3))(4), G(1)-(Bpz(3))(8), and G(2)-(Bpz(3))(16) with [{Rh(mu-Cl)(nbd)}(2)] to give the neutral rhodadendrimers [Si{(CH(2))(3)SiMe(2)(CH(2))(3)Bpz(3)Rh(nbd)}(4)] G(0)-(Bpz(3)Rh)(4), G(1)-(Bpz(3)Rh)(8) and G(2)-(Bpz(3)Rh)(16) as stable solids in excellent yields. Following this protocol, mixed rhodium/iridium metallodendrimers can be prepared.     

A series of [3 + 2] cycloaddition products from the reaction of rhenium oxo complexes with diphenyl ketene

The reaction of rhenium (VII) trioxo complexes containing the ligand sets scorpionate, [HB(pz)3]ReO3 (6), [Ph-B(pz)3]ReO3 (7), and [[HC(pz)3]ReO3][ReO4] (8) and pyridine/pyridine-type ligands [(4,7-diphenyl-1,10-phen)(Br)ReO3] (12), [(4,4'-di-tert-butyl-2,2'-dipyridyl)(Cl)ReO3] (13), and [(py)2Re(Cl)O3] (4), with diphenyl ketene, has led to the isolation of six novel [3 + 2] cycloaddition products. These air-stable solids 9-11 and 15-17 are the result of [3 + 2] addition of the O=Re=O motif across the ketene C=C double bond. Five of the six [3 + 2] cycloaddition products have been structurally characterized by single-crystal X-ray diffraction and in all cases by 13C NMR and IR spectroscopies.     

Condensations of γ-Acetylacetonephosphonium Ylide (1-(Triphenylphosphoranylidene) pentane-2,4-dione) with Carbonyl Compounds

2,4-Dioxopentyltriphenylphosphonium bromide reacted with aqueous sodium hydrogencarbonate in dichloromethane to give, in almost quantitative yield, 1-(triphenylphosphoranylidene) pentane-2,4-dione. Dianion Wittig- and Michael Wittig condensations of the last mentioned phosphonium ylide with carbonyl compounds gave unsaturated 2,4-diketones which were almost totally enolised in deutero chloroform as 4-hydroxy-2-oxo-3,5-dienes (24–70% yields). These products closely resembled the type of compounds derived from similar condensations with alkyl 3-oxo-4-(triphenylphosphoranylidene)butanoate.     

Diazeniumdiolate ions as leaving groups in anomeric displacement reactions: a protection-deprotection strategy for ionic diazeniumdiolates

Diazeniumdiolate ions [R2N-N(O)=N-O-] are of growing interest pharmacologically for their ability to generate up to two molar equivalents of bioactive nitric oxide (NO) spontaneously on protonating the amino nitrogen. Accordingly, their stability increases as the pH is raised. Here we show that the corresponding beta-glucosides [R2N-N(O)=N-O-Glc] decreased in stability with pH; when R2N was diethylamino, the rate equation was kobs = ko + kOH- [OH-], where ko = 7.8 x 10-7 s-1 and kOH- = 5.3 x 10-3 M-1 s-1. The primary products were 1,6-anhydroglucose and the regenerated R2N-N(O)=N-O- ion. The results were qualitatively similar to those of beta-glucosyl fluoride and p-nitrophenoxide, whose hydrolyses have been rationalized as proceeding via a glycal oxide intermediate. This chemistry offers a convenient strategy for protecting heat- and acid-sensitive diazeniumdiolate ions during manipulations that would otherwise destroy them. As an example, a poly(urethane) film that generated NO in physiological buffer at a surface flux comparable to that of the mammalian vascular endothelium was prepared by glucosylating the ionic diazeniumdiolate group attached to the diol monomer before reacting it with the bis-isocyanate, then removing the saccharide with base when the protecting group was no longer needed.     

Efficient Synthesis of N‐Substituted 2,4‐Azepandione Ring System as an Active Intermediate for Heterocyclic Syntheses

An improved efficient synthesis for 2,4‐azepandiones ( 3 , 8 , and 14 ) could be achieved by a careful control of the reaction conditions to cyclize ethyl 4‐(N‐acetylarylamino) butanoate ( 1 , 7 , and 13 ), respectively. The ethyl 4‐arylamino butanoate ( 9 or 12 ) was prepared by stirring the ethyl 4‐bromobutanoate and substituted anilines at room temperature. Then, they were acetylated with acetyl chloride and triethylamine under the conditions that avoid the formation of 2‐pyrrolidinone derivatives 10 . Due to the rapid decomposition of the acetylated product ( 7 or 13 ) to its starting material ( 9 or 12 ), the reaction mixture is directly transferred without workup to the next cyclization step. The azepandione synthesis is favored by using a weak base at low temperature, where it is in a competition with the other modes of ring closure. The structures of the new compounds were supported by correct analytical and spectral data.     

Water-soluble polymers. 71. pH responsive behavior of terpolymers of sodium acrylate,acrylamide, and the zwitterionic monomer 4-(2-acrylamido-2-methylpropanedimethylammonio)butanoate

Terpolymers of sodium acrylate (NaA), acrylamide (AM), and the zwitterionic monomer 4-(2-acrylamido-2-methylpropanedimethylammonio) butanoate (AMPDAB) were prepared by the free radical polymerization in 0.5M NaBr aqueous solution using potassium persulfate as the initiator. The feed ratio of AMPDAB : NaA : AM was varied from 5 : 5 : 90 to 40 : 40 : 20 mol %, with the total monomer concentration held constant at 0.45M. Terpolymer compositions were determined by ¹³C NMR. Molecular weights varied from 3.0 × 10⁵ to 9.7 × 10⁶ g/mol. All terpolymers were soluble in deionized water and salt solutions at all pH values. The dilute and semidilute solution behavior of the terpolymers was studied as a function of composition, pH, and added electrolytes. Polyelectrolyte behavior was observed for all terpolymers at pH 8.5, as evidenced by high viscosity values at low polymer concentrations and viscosity decrease in the presence of added electrolytes. The reduced viscosity as a function of decreasing pH exhibits a minimum as the terpolymer undergoes a polyanion/polyzwitterion/polycation transition. Comparison of the solution behavior of the terpolymers to terpolymers of 3-(2-acrylamido-2-methylpropane dimethylammonio)-1-propane sulfonate (AMPDAPS), AM, and NaA (AADAPS series) as well as copolymers of AMPDAB and AM (AMPDAB series) have been made. © 1997 John Wiley & Sons, Inc.     

泰地唑胺的合成工艺改进

以4-溴-3-氟苯胺为原料,用氯甲酸苄酯保护氨基后,采用一锅两步法制得关键中间体--N-苄氧羰基-3-氟-4-［2-(2-甲基四唑-5-基)吡啶-5-基］苯胺（6）; 6在二异丙基氨基锂作用下与(R)-丁酸缩水甘油酯经环合反应合成了泰地唑胺,总收率53.2%,含量98.5%,其结构经¹H NMR和LC-MS确证。     

Enediyne isomers of tetraethynylethene

Three isomers of tetraethynylethene (1, C10H4) have been prepared by palladium-catalyzed Negishi coupling of a trimethylsilylbutadiynyl zinc reagent with a bromoalkene, followed by mild deprotection with potassium carbonate in methanol. The unsubstituted enynes, 3-ethynyloct-3-ene-1,5,7-triyne (2), trans-dec-5-ene-1,3,7,9-tetrayne (3), and cis-dec-5-ene-1,3,7,9-tetrayne (4), exhibit modest stability at -20 degrees C but decompose rapidly at room temperature. Electronic absorption spectra of 2, 3, and 4 reveal a characteristic vibronic progression at 260-320 nm. Spectral features at shorter wavelength discriminate among the isomers, and permit the assignment of 2 and 3 as apparent dimerization products of triplet carbene H-CC-C-CC-H in matrices at low temperature. Computed relative energies of these C10H4 isomers (MP2/6-31G) are 1 (14.0 kcal/mol), 2 (6.8 kcal/mol), 3 (0.0 kcal/mol), and 4 (1.0 kcal/mol).     

Significantly enhanced reactivities of the nucleophilic substitution reactions in ionic liquid

We have investigated the reactivities of various metal fluorides in the nucleophilic fluorination of 2-(3-methanesulfonyloxypropyl)naphthalene (1) as a model compound in the presence of 1-n-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]). The higher periodic alkali metal fluorides demonstrate greater reactivity. The fluorination using CsF among the alkali metal fluorides was completed in 20 min, affording the desired product 2-(3-fluoropropyl)naphthalene (2a, 95%) without any byproducts. However, the fluorinations using alkali earth, transition, and low periodic alkali metal fluorides under the same conditions occurred rarely or not at all. We have also carried out the various facile nucleophilic substitutions such as halogenations, acetoxylation, nitrilation, and alkoxylations of mesyloxyalkane 1 and 2-(3-bromopropyl)naphthalene (6) at the primary aliphatic position using the potassium halides, acetate, cyanide, and alkoxides, respectively, in the presence of ionic liquids. These reactions provided the desired products, such as 2-(3-halopropyl)naphthalenes 5-7 (95% for Cl, 96% for Br, and 93% for I), 2-(3-acetoxypropyl)naphthalene (8, 95%), 2-(3-cyanopropyl)naphthalene (9, 93%), and 2-(3-methoxypropyl)naphthalene (10, 92%).