Microwave-assisted synthesis of 5-trichloromethyl substituted 1-phenyl-1H-pyrazoles and 1,2-dimethylpyrazolium chlorides

A series of five 5-trichloromethyl-1-phenyl-1H-pyrazoles and six 5-trichloromethyl-1,2-dimethylpyrazolium chlorides have been synthesized in 80-98% yield by environmentally benign microwave induced techniques involving the cyclocondensation of 4-alkoxy-1,1,1-trichloro-3-alken-2-ones [Cl₃C(O)C(R²)=C(R¹)OR, where R²=H, Me; R¹=H, alkyl, phenyl and R=Me, Et] with phenyl hydrazine and 1,2-dimethylhydrazine dihydrochloride, respectively, using toluene as solvent. The use of microwave and classical methods are comparable for making pyrazoles, but the formation of pyrazolium chlorides can be achieved in a significant shorter time, and in some cases better yield.     

Iminophosphines: synthesis, formation of 2,3-dihydro-1H-benzo[1,3]azaphosphol-3-ium salts and N-(pyridin-2-yl)-2-diphenylphosphinoylaniline, coordination chemistry and applications in platinum group catalyzed Suzuki coupling reactions and hydrosilylations

The aprotic and protic bi- and multidentate iminophosphines 2-Ph₂PC₆H₄N=CR¹R² (R¹=H, R²=Ph=2a; R¹=Me R²=Ph=2b; R¹=H, R²=2-thienyl=2c; R¹=H, R²=C₆H₄-2-PPh₂=2d; R¹=H, R²=C₆H₄-2-OH=2e, R¹=H, R²=C₆H₄-2-OH-3-Bu^t=2f; R¹=H, R²=CH₂C(O)Me=2g) have been prepared by the acid catalyzed condensation of 2-(diphenylphosphino)aniline with the corresponding aldehyde–ketone. Iminophosphine 2d can be reduced with sodium cyanoborohydride to give the corresponding amino-diphosphine 2-Ph₂PC₆H₄N(H)CH₂C₆H₄-2-PPh₂ (2h). In the presence of a stoichiometric quantity of acid, 2-(diphenylphosphino)aniline reacts in an unexpected manner with benzaldehyde, salicylaldehyde, or acetophenone to give the corresponding 2,3-dihydro-1H-benzo[1,3]azaphosphol-3-ium salts and with pyridine-2-carboxaldehyde to give N-(pyridin-2-ylmethyl)-2-diphenylphosphinoylaniline, the latter of which has been characterized by single-crystal X-ray crystallography, as its palladium dichloride derivative. The attempted condensation of 2-(diphenylphosphino)aniline with pyridine-2-carboxaldehyde to give the corresponding pyridine-functionalized iminophosphine resulted in an unusual transformation involving the diastereoselective addition of two equivalents of aldehyde to give 1,2-dipyridin-2-yl-2-(o-diphenylphosphinoyl)phenylamino-ethanol, which has been characterized by a single-crystal X-ray structure determination. The bidentate iminophosphine 2-Ph₂PC₆H₄N=C(H)Ph reacts with [(cycloocta-1,5-diene)PdClX] X=Cl, Me) to give [Pd{2-Ph₂PC₆H₄N=C(H)Ph}ClX] and the imino-diphosphine 2-Ph₂PC₆H₄N=C(H)C₆H₄-PPh₂ reacts with [(cycloocta-1,5-diene)PdClMe] to give [Pd{2-Ph₂PC₆H₄N=C(H)C₆H₄---PPh₂}ClMe] and each has been characterized by single-crystal X-ray crystallography. The monobasic iminophosphine 2-Ph₂PC₆H₄N=C(Me)CH₂C(O)Me reacts with [Ni(PPh₃)₂Cl₂] in the presence of NaH to give the phosphino–ketoiminate complex [Ni{2-Ph₂PC₆H₄N=C(Me)CHC(O)Me}Cl], which has been structurally characterized. Mixtures of iminophosphines 2a–h and a palladium source catalyze the Suzuki cross coupling of 4-bromoacetophenone with phenyl boronic acid. The efficiency of these catalysts show a marked dependence on the palladium source, catalysts formed from [Pd₂(OAc)₆] giving consistently higher conversions than those formed from [Pd₂(dba)₃] and [PdCl₂(MeCN)₂]. Catalysts formed from neutral bi- and terdentate iminophosphines 2a–d gave significantly higher conversions than those formed from their monobasic counterparts 2e–f. Notably, under our conditions the conversions obtained with 2a–c compare favorably with those of the standards; catalysts formed from tris(2-tolyl)phosphine and tris(2,4-di-tert-butylphenyl)phosphite and a source of palladium. In addition, mixtures of [Ir(COD)Cl]₂ and 2a–h are active for the hydrosilylation of acetophenone; in this case catalysts formed from monobasic iminophosphines 2e–f giving the highest conversions.     

Syntheses and reactivities of azido coordinated CpCo(dithiolene) complexes

Azido coordinated dithiolene complexes [CpCo(N₃){S₂C₂(CO₂Me)₂}(S-CHR¹R²)], where R¹, R² = H (4a); R¹ = H, R² = SiMe₃ (4b); R¹ = H, R² = CO₂Et (4c), were synthesized by the reactions of the corresponding Cl⁻ coordinated precursors [CpCo(Cl){S₂C₂(CO₂Me)₂}(S-CHR¹R²)] (3a-3c) with sodium azide. The Cl⁻ coordinated complex 3d (R¹, R² = CO₂Me) did not produce any N₃⁻ coordinated complexes but formed the CR¹R²-bridged alkylidene adduct [CpCo{S₂C₂(CO₂Me)₂}(CR¹R²)] (2d; R¹, R² = CO₂Me). The structure of 4a was determined by X-ray diffraction study. In the molecular structure of 4a, the coordinated N₃⁻ ligand and CHR¹R² group were located at the same side with respect to the dithiolene ring (syn form), although the corresponding Cl⁻ precursor (3a; R¹, R² = H) was anti form. A structural conversion of syn/anti was conceivable during the Cl⁻/N₃⁻ ligand exchange. Thermal (80 °C) and photochemical reactions (Hg lamp) of 4a-4c were performed. Among them, 4c was relatively well reacted compared with the others to form the CR¹R²-bridged alkylidene adduct (2c; R¹ = H, R² = CO₂Et), followed by a formal HN₃ elimination, and the reaction also produced non-adduct of the cobalt dithiolene complex [CpCo{S₂C₂(CO₂Me)₂}] (1). The electrochemical 1e⁻ reduction of 4c underwent a formal N₃⁻ ligand elimination, and successive second reduction caused the CHR¹R² group elimination or reformed the CR¹R²-bridged alkylidene adduct 2c.     

Preparation of poly(biphenylene vinylene) type polymers by Ni‐promoted polycondensation and their basic optical properties

Ni(0)‐complex promoted dehalogenation polymerization of 1,2‐bis(4‐bromophenyl)ethylene derivatives gave poly(p‐biphenylene vinylene) type polymers, [—C₆H₂R—CR² = CR²—C₆H₂R—)_n (P(R¹,H) and P(H,R²) ], having substituents (R¹ = Me, Et, CHMe₂, and n‐C₈H₁₇, R² = Me, Et, n‐C₆H₁₃, n‐C₁₁H₂₃, and Ph) at the benzene ring or vinylene group in 90–99% yields. The polymers were soluble in organic solvents such as CHCl₃, dimethylformamide, and tetrahydrofuran, and gave M_n of 2.4–5.3 × 10³ in gel permeation chromatography analysis. The absorption peak of the polymers appeared at a longer wavelength than that of the corresponding monomers by about 30 nm due to the expansion of the π‐conjugation system. The polymers were photoluminescent in solutions and in their films, emitting blue or green light. P(R¹,H)s gave higher quantum yields (Φ = 0.35–0.51) than P(H,R²) s in CHCl₃. P(H,R²) s showed a large Stokes shift (9600–13,500 cm⁻¹) in their photoluminescence. Single‐layer and multilayer light emitting diodes using vacuum deposited thin film of P(H,Ph) were prepared. Polymers with long alkyl substituents formed an ordered structure in the solid state as judged from their XRD patterns. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1493–1504, 2000     

Enol ethers and acetals: acylation with dichloroacetyl,acetyl and benzoyl chloride in ionic liquid medium

Synthesis of 4-alkoxy-1,1-dichloro-3-alken-2-ones [CHCl₂C(O)C(R²)C(R¹)-OR, where R, R¹, R² = Et, H, H; Me, Me, H; Et, H, Me; Me, –(CH₂)₂–; Me, –(CH₂)₃–; Et, Et, H; Et, Bu, H; Et, i-Pr, H; Et, i-Bu, H; Me, Ph, H; Me, thien-2-yl, H] from acylation of enol ethers and acetals with dichloroacetyl chloride, in ionic liquid ([BMIM][BF₄] or [BMIM][PF₆]) is reported. The synthesis of alkenones [R³–C(O)C(R²)C(R¹)-OR], where R/R¹/R²/R³ = Et/H/H/Ph, t-Bu/H/H/Ph, Me/-(CH₂)₄/Ph, Me/-(CH₂)₄/Me] from the reaction of enol ethers with benzoyl chloride or acetyl chloride, in ionic liquid [BMIM][BF₄], is also reported. Last products are described for the first time.     

Preparation of new 2‐amino‐ and 2,3‐diamino‐pyridine trifluoroacetyl enamine derivatives and their application to the synthesis of trifluoromethyl‐containing 3H‐pyrido[2,3‐b][1,4] diazepinols

The synthesis of a novel series of the intermediates N²(N³)‐[1‐alkyl(aryl/heteroaryl)‐3‐oxo‐4,4,4‐trifluoroalk‐1‐en‐1‐yl]‐2‐aminopyridines [F₃CC(O)CH?CR¹(2? NH?C₅H₃N)] and 2,3‐diaminopyridines [F₃CC(O)CH?CR¹(2‐NH₂‐3‐NH? C₅H₃N)], where R¹ = H, Me, C₆H₅, 4‐FC₆H₄, 4‐CIC₆H₄, 4‐BrC₆H₄, 4‐CH₃C₆H₄, 4‐OCH₃C₆H₄, 4,4′‐biphenyl, 1‐naphthyl, 2‐thienyl, 2‐furyl, is reported. The corresponding series of 2‐aryl(heteroaryl)‐4‐trifluoromethyl‐3H‐pyrido[2,3‐b][1,4]diazepin‐4‐ols obtained from intramolecular cyclization reaction of the respective trifluoroacetyl enamines or from the direct cyclocondensation reaction of 4‐methoxy‐1,1,1‐trifluoroalk‐3‐en‐2‐ones with 2,3‐diaminopyridine, under mild conditions, is also reported.     

Mass spectra of esters of α-hydroxy and α-methoxy acids

The most abundant fragment produced by electron bombardment of esters of the type R¹R²C(OR³)CO₂R⁴ is the R¹R²C = \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^{{\rm + } \cdot } $\end{document}R³ ion. Methyl glycollate (R¹ = R² = R³ = H, R⁴ = Me) eliminates the HCO˙ radical by a complex rearrangement involving the methylenic hydrogen atoms. The methyl and ethyl esters of methoxyacetic acid (R¹ = R² = H, R³ = Me, R⁴ = Me or Et) eliminate formaldehyde by the McLafferty rearrangement.     

Cobalt metallocycles: IV. Ring opening of cobaltacyclopentadienes by addition of SiH,SH,NH and CH to the diene moiety

Cobaltacyclopentadiene complexes, (η⁵-C₅H₅)(PPh₃)($\text{CoCR}{}^1\text{CR}{}^2\text{CR}{}^2\text{C}$R¹) (R¹, R² =; Ph, Me, CO₂Me), reacted with RH (RH: triethylsilane, thiocresol, dimethyl- and ethylene-thiourea, pyrrole, thiophene) to give diene complexes, (η⁵-C₅H₅)(η⁴-HCR¹CR²CR²CR¹R)Co, or uncomplexed, highly substituted butadiene derivatives, HCR¹CR²CR²CR¹R. The reaction with thiourea proceeded catalytically in the presence of excess of diphenylacetylene although turn-over of the catalyst was small.     

Fluoro-olefin chemistry Part 20 [1]. Reaction of hexafluoropropene with alcohols

Reaction of hexafluoropropene (HFP) with a series of alcohols under thermal, photochemical or peroxide-initiated conditions affords the 1:1 adducts CF₃CHFCF₂CR¹R²OH (R¹ = H, R² = H, Me, Prⁿ or CF₃; R¹ = Me, R² = Me or Et) in high yield via a radical chain mechanism. Adduct are not formed with the alcohols (CF₃)₂CHOH and CF₃CHFCF₂CH₂OH. Other 1:1 adducts of structure CHF₂CF(CF₃)CH₂OH and CH₃(C₂H₃CF₂CHFCF₃)CH₂OH are formed as minor products in the methanol and $\text{n}$-butanol reactions, respectively.     

The nature of resonance and hyperconjugation for cyclic β-silyl substituted carbocations: NBO, NRT, EDA, and NMR studies

The stabilities of various cyclic β-silyl carbocations and their desilylated analogues, relative to tert-butyl cation, were calculated in the gas phase at B3LYP/6-311++G** level of theory. Natural bond orbital (NBO) theory was used for the calculation of charges and bond orders. The contribution of carbenium ion [R¹R²C⁺–CR³R⁴Si(Me)₃] and silylium ion [R¹R²C=CR³R⁴ Si(Me) ₃ ⁺ ] to the resonance structures was investigated by natural resonance theory (NRT). The localized molecular orbitals energy decomposition analysis (LMO-EDA) was employed to estimate the bond dissociation energy of β-silyl carbocations to R¹R²C=CR³R⁴ and Si(Me) ₃ ⁺ fragments via the MP2/6-311++G** method. The silylium ion is the most important resonance structure of β-silyl cycloalkyl (cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl) and cyclopentadienyl cations. In the case of β-silyl phenylcyclopropyl, benzocyclobutyl, cyclopropenyl, and tropylium ions, the carbenium ion is the major contributor (due to the delocalization of positive charge). The calculated ²⁹Si and ¹³C nuclear magnetic resonance (NMR) chemical shifts complement these results.     

Darstellung und eigenschaften von und reaktionen mit metallhaltigen heterocyclen XX. Darstellung,eigenschaften und kristallstruktur von λ4-thia-λ5-phospha-h2-metallabicyclo[2.2.1]heptadienen und ihre verwendung zur synthese von metallorganischen und organischen verbindungen

The novel λ⁴-thia-λ⁵-phospha-h²-manganabicyclo[2.2.1]heptadienes (OC)₃Mn[$\text{CR}{}^2\text{CR}{}^2\text{CR}{}^2\text{CR}{}^2\text{PR}{}^1{}_2\text{S}$] (R¹ = CH₃, C₆H₅; R² = CO₂CH₃, CO₂C₂H₅, CO₂C₆H₁₁) are formed by action of the activated alkynes R²C  CR² on the heterocycles [(OC)₄MnPR¹₂S]₂ via the isolable, five-membered heterometallacyclopentadienes (OC)₄$\text{MnSPR}{}^1{}_2\text{C(R}{}^2\text{)C}$(R²). The compound with R¹ = CH₃ and R² = CO₂CH₃ crystallizes in the triclinic space group P$\text{1}$ with Z = 2 and separates quantitatively the thiophene derivative $\text{CR}{}^2\text{CR}{}^2\text{CR}{}^2\text{CR}{}^2\text{S}$ under CO pressure or by reaction with (NH₄)₂Ce(NO₃)₆. The use of various acetylenes and of acetylenes with different alkyl groups yields the unsymmetric substituted manganabicycloheptadienes (OC)₃Mn[$\text{CR}{}^4\text{CR}{}^3\text{CR}{}^2\text{CR}{}^2\text{P(CH}{}_3\text{)}{}_2\text{S}$] (R² = CO₂CH₃, R³ = R⁴ = CO₂C₂H₅; R² = R⁴ = CO₂CH₃, R³ = H). With propionic acid methylester the alkyne insertion proceeds regiospecifically. With Raney nickel selective S elimination under ring contraction and formation of the λ⁴-phospha-h²-manganabicyclo[2.1.1]hexenes (OC)₃Mn[$\text{CR}{}^2\text{CR}{}^3\text{CR}{}^2\text{CR}{}^2\text{P}$R¹₂] (R¹ = CH₃: R² = R³ = CO₂CH₃, CO₂C₂H₅; R² = CO₂CH₃, R³ = H; R¹ = C₆H₅: R² = R³ = CO₂C₂H₅) occurs. (OC)₃Mn[$\text{CR}{}^2\text{CR}{}^3\text{CR}{}^2\text{CR}{}^2\text{P}$(CH₃)₂] (R² = R³ = CO₂CH₃) crystallizes in the monoclinic space group P2₁/m with Z = 2. The IR and NMR spectra of the heterocycles are discussed in detail.     

Carboncarbon bond formation by radical addition-fragmentation reactions of O-tert-alkyl enols and O-cyclopropylcarbinyl enols

Terminal alkenes of the type H₂CC(OR¹)X, in which R¹ is a tertiary alkyl or a 1-cyclopropylethyl group and X=Ph, OSiMe₂Bu^t, OEt or H, undergo radical-chain reactions with organic halides R²Hal to give carbonyl compounds R²CH₂C(O)X.     

Nickel‐Catalyzed Borylative Coupling of Alkynes,Enones, and Bis(pinacolato)diboron as a Route to Substituted Alkenyl Boronates

Three‐component coupling reactions of an alkyne, an enone, and a diboron reagent provide access to highly substituted alkenyl boronates in good to excellent yields (see scheme). The coupling is highly regio‐ and stereoselective, and the products are amenable to further functional‐group transformations. R¹,R²=H, alkyl, aryl, CO₂Me; R³=alkyl, Ph; R⁴,R⁵=H, alkyl.

     

Formation of 5-phenyl-1,2-dithiole-3-thione from molybdenum dithiopropiolato complexes

Molybdenum dithiopropiolato complexes, [(η⁵-C₅R₄R^′)Mo(CO)₂(η²-S₂CCCPh)] (R=H, R^′=Me 1a, R=R^′=H 1b; R=R^′=Me 1c) react with trimethylamine-N-oxide (TMNO · 2H₂O) under mild thermolysis to form 5-phenyl-1,2-dithiole-3-thione (2). The reaction proceeds through the formation of the oxo-complexes, [(η⁵-C₅R₄R^′)Mo(O)(η³-S₂CCCPh)] (R=H, R^′=Me 3a, R=R^′=H 3b; R=R^′=Me 3c). Direct reaction of 3a-c with TMNO · 2H₂O under thermolysis also results in formation of 2.     

Chemistry of Fischer-type rhenacyclobutadiene complexes. II. Reactions with alkynes and sulfonium ylides, and rearrangements induced by nitriles and pyridine

Further investigations into the chemistry of the rhenacyclobutadiene complexes (CO)₄Re(η²-C(R)C(CO₂Me)C(X)) (1: R=Me, X=OEt (1a), O(CH₂)₃CCH (1b), NEt₂ (1c); R=CHEt₂, X=OEt (1d); R=Ph, X=OEt (1e)) are reported. Reactions of 1 with alkynes at reflux temperature of toluene and at ambient temperature either under photochemical conditions or in the presence of PdO yield ring-substituted η⁵-cyclopentadienylrhenium tricarbonyl complexes, 2. The symmetrical alkynes R^′CCR^′ (R^′=Ph, Me, CO₂Me) afford the pentasubstituted complexes (η⁵-C₅(Me)(CO₂Me)(OEt)(Ph)(Ph))Re(CO)₃ (2d), (η⁵-C₅(Me)(CO₂Me)(OEt)(Me)(Me))Re(CO)₃ (2e), (η⁵-C₅(Me)(CO₂Me)(OEt)(CO₂Me)(CO₂Me))Re(CO)₃ (2f), and (η⁵-C₅(Me)(CO₂Me)(NEt₂)(CO₂Me)(CO₂Me))Re(CO)₃ (2i) on reaction with the appropriate 1, whereas the unsymmetrical alkynes R^′CCR″ (R^′=Ph; R″=H, Me) give either only one, (η⁵-C₅(Me)(CO₂Me)(OEt)(Ph)H)Re(CO)₃ (2a)), or both, (η⁵-C₅(Me)(CO₂Me) (OEt)(Ph)(Me))Re(CO)₃ (2b) and (η⁵-C₅(Me)(CO₂Me)(OEt)(Me)(Ph))Re(CO)₃ (2c), (η⁵-C₅(Ph)(CO₂Me)(OEt)(Ph)H)Re(CO)₃ (2g) and (η⁵-C₅(Ph)(CO₂Me)(OEt)(H)(Ph))Re(CO)₃ (2h), of the possible products of [3 + 2] cycloaddition of alkyne to η²-C(R)C(CO₂Me)C(X). Thermolysis of (CO)₄Re(η²-C(Me)C(CO₂Me)C(O(CH₂)₃CCH)) (1b) containing a pendant alkynyl group proceeds to (η⁵-C₅(Me)(CO₂Me)(O(CH₂)₃)H)Re(CO)₃ (2j), a η⁵-cyclopentadienyl-dihydropyran fused-ring product. Competition experiments showed that each of PhCCH and MeO₂CCCCO₂Me reacts faster than PhCCPh with 1a. The results with unsymmetrical alkynes are rationalized by steric properties of substituents at the CC and ReC bonds and by a preference of ReC(Me) over ReC(OEt) to undergo alkyne insertion. A mechanism is proposed that involves substitution of a trans CO by alkyne in 1, insertion of alkyne into ReC bond to give a rhenabenzene intermediate, and collapse of the latter to 2. Complexes 1a and 1d undergo rearrangement in MeCN at reflux temperature to give rhenafuran-like products, (CO)₄Re(κ²-OC(OMe)C(CHCR₂)C(OEt)) (R=H (3a) or Et (3b)). The reaction of 1d also proceeds in EtCN, PhCN, and t-BuCN at comparable temperature, but is slower (especially in t-BuCN) than in MeCN. In pyridine at reflux temperature, 1a undergoes a similar rearrangement, with CO substitution, to give (CO)₃(py)Re(κ²-OC(OMe)C(CHCEt₂)C(OEt)) (4). A mechanism is proposed for these reactions. The sulfonium ylides Me₂SCHC(O)Ph and Me₂SC(CN)₂ (Me₂SCRR^′) react with 1a in acetonitrile at reflux temperature by nucleophilic addition of the ylide to the ReC(Me) carbon, loss of Me₂S, and rearrangement to a rhenafuran-type structure to yield (CO)₄Re(κ²-OC(OMe)C(C(Me)CRR^′)C(OEt)) (R=H, R^′=C(O)Ph (5a); R=R^′CN (5b)). All new compounds were characterized by a combination of elemental analysis, mass spectrometry, and IR and NMR spectroscopy.     

Palladium(II) compounds with planar chirality. X-Ray crystal structures of (+)-(R)-[{(η5-C5H4)–CHN–CH(Me)–C10H7}Fe(η5-C5H5)] and (+)-(Rp,R)-[Pd{[(Et–CC–Et)2(η5-C5H3)–CHN–CH(Me)–C10H7]Fe(η5-C5H5)}Cl]

A wide variety of planar chiral cyclopalladated compounds of general formulae [Pd{[(η⁵-C₅H₃)–CHN–CH(Me)–C₁₀H₇]Fe(η⁵-C₅H₅)}Cl(L)] (with L=py-d₅ or PPh₃), [Pd{[(η⁵-C₅H₃)–CHN–CH(Me)–C₁₀H₇]Fe(η⁵-C₅H₅)}(acac)] or [Pd{[(R¹–CC–R²)₂(η⁵-C₅H₃)–CHN–CH(Me)–C₁₀H₇]Fe(η⁵-C₅H₅)}Cl] (with R¹=R²=Et; R¹=Me, R²=Ph; R¹=H, R²=Ph; R¹=R²=Ph; R¹=R²=CO₂Me or R¹=CO₂Et, R²=Ph) are reported. The diastereomers {(R_p,R) and (S_p,R)} of these compounds have been isolated by either column chromatography or fractional crystallization. The free ligand (R)-(+)-[{(η⁵-C₅H₄)–CHN–CH(Me)–C₁₀H₇}Fe(η⁵–C₅H₅)] (1) and compound (+)-(R_p,R)-[Pd{[(Et–CC–Et)₂(η⁵-C₅H₃)–CHN–CH(Me)–C₁₀H₇]Fe(η⁵-C₅H₅)}Cl] (7a) have also been characterized by X-ray diffraction. Electrochemical studies based on cyclic voltammetries of all the compounds are also reported.     

Mass spectra of new heterocycles: VIII. Fragmentation of 6-alkoxy- and 6-aryl(hetaryl)-3H-azepines under electron impact

The electron impact mass spectra of previously unknown 2-alkyl-6-alkoxy-, 2,3-trimethylene-6-alkoxy- and 2-alkyl-6-aryl(hetaryl)-3H-azepines were studied. All compounds give rise to stable molecular ions (I _rel = 44–100%) whose fragmentation pattern is determined mainly by the substituent on C⁶. Decomposition of the molecular ions derived from 6-alkoxy derivatives (R¹ = MeO, EtO, i-PrO) follows general relations typical of alkyl ethers. The main characteristic peaks in the mass spectra of 2-methyl-6-aryl- and 2-methyl-6-hetaryl-3H-azepines (R¹ = Ph, 1H-pyrrol-1-yl, 5-methylthiophen-2-yl) belong to even-electron rearrangement ions [M − H]⁺ and [M − Me]⁺, which have conjugated bi- and tricyclic structures, and products of their subsequent decomposition. Substituents in positions 2 (R²) and 3 (R⁴) [R⁴ = H, R² = Me, Et; R²R⁴ = (CH₂)₃] bring some specificity to the fragmentation pattern, but their contribution is not crucial. Original Russian Text ? L.V. Klyba, N.A. Nedolya, O.A. Tarasova, E.R. Zhanchipova, O.G. Volostnykh, 2009, published in Zhurnal Organicheskoi Khimii, 2009, Vol. 45, No. 4, pp. 610–621. For communication VII, see [1].     

Synthesis of amidine complexes by metal-mediated addition of amino acid esters to coordinated nitriles

The reaction of the nitrile platinum(IV) complex trans-[PtCl₄(EtCN)₂] with amino acid esters H₂NC(R¹)(R²)CO₂Me (R¹ = R² = H, H-Me, Me-Me, H-Ph) and H₂NCH₂CH₂CO₂Me in CH₂Cl₂ produces the amidine complexes trans-[PtCl₄{ Z-NH=C(Et)NHC(R¹)(R²)CO₂Me}₂] and trans-[PtCl₄{ Z-NH=C(Et)NHCH₂CH₂CO₂Me}₂], which were isolated in 70–80% yields and characterized by elemental analysis, mass spectrometry, IR spectroscopy, and ¹H and ¹³C{¹H} NMR spectroscopy. The structures of the complexes with R¹ = R² = H (1), R¹ = H, R² = Me (2), and R¹ = H, R² = Ph (4) were established by X-ray diffraction analysis.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 601–605, March, 2005.     

Reaction of 3-oxo-3-R<Superscript>1</Superscript>-<Emphasis Type="Italic">N</Emphasis>-R<Superscript>2</Superscript>-propanethioamides with 2-amino-5-R-pyridines

Direction of a reaction between 3-oxo-3-R¹-N-R²-propanethioamides and 2-amino-5-R-pyridines in acetic acid depends on the structure of initial thioamides: at R¹ = Me, R² = Ar, Et 2-methyl-7-R-4H-pyrido[1,2-a]-pyrimidine-4-thiones are obtained, and at R¹ = Ar, R² = Me form 1-methyl-5-(N-methylaminothiocarbonyl)-4,6-diaryl-1,2-dihydropyridine-2-thiones.     

Olefin isomerisation by group via metals

2-(MeR¹CCR²)-and 2-(CH₂CR¹CH₂CH₂)-pyridine (R¹,R² = H or Me) undergo 1,2-double-bond shifts and 2-(CH₂CHCH₂CH₂CH₂)-pyridine undergoes a 1,3-double-bond shift on displacement of norbornadiene from [M(CO)₄norb] (M = Cr, Mo or W) to give complexes of the type [M(CO)₄LL'] (LL' = 2-(allyl)or 2-(substituted allyl)-pyridine), which do not exhibit conformational isomerism involving the plane of the coordinated olefin.