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The reaction pathway between the components of the catalytic system Cp 2 TiCl 2 -LiAlH 4 -unsaturated hydrocarbon, depends considerably on the nature of the reaction medium. In dienes which are able to form stable η 3 -allyltitanocene derivatives, these represents the main reaction product; they are catalytically active in the double bond shifts. In dienes not forming stable η 3 -allyltitanocene derivatives and in α-olefins, the catalytically-active η 1 -alkenyl- and alkyl-titanocenes are transiently formed, deactivating rapidly to give the [(C 5 H 5 )(C 5 H 4 )TiHAlR 2 ] 2 complexes and minor amounts of η 3 -allyltitanocene derivatives in a side reaction involving intermolecular hydrogen transfer. In all α-olefinic hydrocarbons, the formation of alkyl-, η 1 -alkenyl- or η 3 -allyl-titanocene derivatives is preceded by the hydroalumination reaction, yielding Cp 2 TiCl 2 AlR 2 complexes. In internal olefins the hydroalumination reaction does not occur and the alkyltitanocenes which are formed catalyze the transformation of (Cp 2 TiCl) 2 into μ-(η 5 : η 5 -fulvalene)-di-μ-chlorobis(η 5 -cyclopentadienyltitanium), thus inducing the self-deactivation of the system.

Methane-, ethene-, and ethynesulfenic acids were generated in the gas phase by flash-vacuum pyrolysis of the corresponding tert-butyl sulfoxides at 400 °C and 10-4 Pa. Benzenesulfenic acid was prepared from phenyl 3-buten-1-yl sulfoxide at 350 °C and 10-4 Pa. The sulfenic acids were characterized by mass spectrometry Threshold ionization energies (IE) were measured as IE(CH3SOH) = 9·07 ± 0·03 eV, IE(CH2=CHSOH) = 8·70 ± 0·03 eV, IE(HCCSOH) = 8·86 ± 0·04 eV, and IE(C6H5SOH) = 8·45 + 0·03 eV. Radical cations [CH3SOH].+, [CH2=CHSOH].+, and [HCCSOH].+ were generated by electron-impact-induced loss of propene from the corresponding propyl sulfoxides and their heats of formation were assessed by appearance energy measurements as 685, 824, and 927 kJ mol-1, respectively. Heats of formation of the neutral sulfenic acids and the S-(O) (C), S-(O) (Cd), S-(O) (Ct) and S-(O) (CB) group equivalents were determined. The experimental data, supported by MNDO calculations, point to sulfenate-like structures (R-S-OH) for the sulfenic acids under study.

The cycloheptatrienyl (tropenyl) radical was generated by the gas-phase pyrolysis of ditropenyl at 473–723 K and was trapped in cocondensed adamantane at 77 K. Well-resolved isotrppic ESR spectra of the tropenyl radical showed a linear temperature dependence of aiso in the range 77–226 K. The tropenylperoxyl radical was obtained if the ditropenyl pyrolysis was carried out in the presence of dioxygen. The anisotropic ESR spectrum of the tropenylperoxyl radical obtained in the adamantane matrix at 77 K was characterized by g1 = 2.035, g2 = 2.009, g3 = 2.002 and a1 = 8.4 G,† a2 = 9.6 G and a3 = 5.35 G. The values of giso and aiso were found experimentally in the freely rotating radical at 130 K to be g = 2.0157 and a = 7.5 G respectively. The hyperfine coupling arises from coupling to the β-H atom via a hyperconjugative mechanism.

Mass spectra of nine of the sixteen possible diastereoisomeric 7-hydroxytricyclo[7.3.0.02,6]dodecanes are reported. The spectra differ considerably in the extent of water elimination from molecular ions. The diastereoisomers which have conformationally flexible cis-anti-cis, cis-anti-trans and cis-syn-trans skeletons exhibit abundant (M-H2O)+. ions. Molecular ions of the rigid trans-anti-trans isomers lose water to a markedly smaller extent, the main fragmentation proceeding via a skeletal cleavage. Effects of conformational mobility are emphasized.

μ-(η5:η5-Fulvalene)-di-μ-hydrido-bis(η5-cyclopentadienyltitanium) (1) can be prepared by the reduction of Cp2TiCl2 with LiAlH4 in methylbenzenes and in tetralin at their boiling temperatures in yields greater than 90%. The reduction proceedsvia the bis(η5-cyclopentadienyl)titanium(III) chloride dimer which is further transformed into the unstable [Cp2TiH] species. Thermal decomposition of the latter accompanied by hydrogen evolution gives rise to (1). μ-(η5:η5-Fulvalene)-μ-hydrido-μ-chloro-bis(η5-cyclopentadienyltitanium), the first fulvalene containing compound observed in the system is formed by hydrido-chloro exchange of (1) with (Cp2TiCl)2 and aluminium chlorohydrides.

The condensation reaction of hydrazobenzene with ethanal yields products of the pyrazolidine structure, III or V, according to whether it is carried out in the absence or presence of alcohols, respectively. Propanal reacts similarly to VIII while no reaction could be achieved with butanal. The structural evidence is based mainly on the mass and 1H NMR spectra which disprove the structures IV and VI, originally suggested by Rassow. The reaction is analogous to the condensation of aliphatic aldehydes with N-phenylhydroxylamine yielding 1,2-oxazolidine derivatives VII.

Hypobromous acid addition to steroid dienes I-VI proceeds in four steps. The reaction commences by the attack on more reactive endocyclic double bond from the α-side yielding intermediary diaxial bromohydrins XXVIII, XXXIV, XL, XLIV, L and LVI via corresponding α-bromonium ions. The 10β-vinyl group of the bromohydrins then reacts with a second equivalent of the reagent forming transient 19-epimeric bromonium ions. The ions generated from I, II, V and VI are cleaved intramolecularly by the hydroxyl group, in accordance with the Markovnikov rule, giving rise to 19-epimeric dibromo epoxides XXXIa and XXXIIa, XXXVII and XXXVIII, LIIIa and LIVa, LIX and LX. By contrast, the ions generated from III and IV are cleaved in an anti-Markovnikov manner to yield dibromo epoxides XLII, XLVII and XLVIII. Products due to formation of a new C-C bond were not observed. The reaction mechanism and differences in the behaviour of the dienes I-VI are discussed.

The electron impact mass spectrum of N,N′-diethyl-N,N′-diphenylurea contains the ion m/z 164 which is of low abundance at normal energy of ionizing electrons but prominent at 15-20eV. The mechanism of its formation has been revealed by means of labelled compounds. It is rationalized in terms of an unusual formation of styrene lost as a neutral molecule.

Two series of methyl phosphineacetates with the general formulae Ph3-nP(CH2CO2Me)n, n = 1–3, and RP(CH2CO2Me)2, R[dbnd]Me, Et, i-Pr, were synthesized by a BF3-catalyzed reaction of the acids or their hydrohalides with methanol. The products were characterized by IR, 1H, 13C and 31P NMR and mass spectra and their properties that are important for the coordination behaviour (basicity, electronic parameters and cone angles) were determined. A new method for cone angle estimation based on a systematic search for crystal structure data was proposed.

The metathesis of methyl 10-undecenoate was studied using the WCl6 + (CH3)4Sn catalyst system. The rate of metathesis and the maximum degree of conversion are affected markedly by the reactions of the ester, and of the other oxygen compounds if present, with tungsten hexachloride. Introduction of an oxygen ligand to the central tungsten atom of the active centre increases the reactivity and stability of the latter, thus affecting positively the initial rate of the metathesis reaction. At the same time, however, the rate of the catalyst deactivation increasing concentration of the ester, whereupon the degree of the conversion decreases. As a result of competition of the two effects, a maximum appears in the dependence of the amount of the ester reacted on the ester-to-tungsten hexachloride ratio.

(η 6 -Benzene)bis(dichloroalanedi-μ-chloro)titanium(II) ( Ia ) and its bromo analogue (Ib) catalyze the cyclotrimerization of butadiene to ( Z,E,E )-1,5,9-cyclododecatriene (CDT) with an overall selectivity as high as 92% and 95%, respectively. The convenient catalytic properties of the complexes, i.e. the high catalytic stability of Ia and the high initial rate induced by Ib , have been optimally combined in mixed chloro-bromo complexes. Isothermal and isobaric kinetic measurements have revealed that the reaction order with respect to butadiene is close to 2.0 while the reaction order with respect to the catalyst approaches 1.0 at extreme dilution and decreases with increasing catalyst concentration. Deactivation of the catalyst results in the separation of insoluble titanium halides. The proposed kinetic scheme includes rapid equilibrium between arene- and bis(butadiene)-titanium(II) complexes, followed by the ratedetermining formation of the intermediate titanium complex with an openchain butadiene dimer and very fast cycloaddition of the third butadiene molecule. The formation of ( Z,E,E )-1,5,9-CDT is accounted for by the cycloaddition of butadiene in an s -( Z )- conformation to an intermediate, which is probably [1,2-bis( syn -η 3 -allyl)ethane]bis(tetrahaloalanate)titanium-(IV) or s η 1 -allyl analogue.

The system Cp2TiCl2−LiAlH4, in the absence of ethereal solvents, catalyzes the intramolecular cyclization of Z,E,E-1,5,9-cyclododecatriene, yielding a mixture of C12 hydrocarbons consisting mainly of cis, anti, cis-and cis, syn, trans-tricyclo [7.3.0.02,6] dodec-7-ene and 5,6,7,8,9,10-hexahydrobenzocyclooctene.

Electron impact spectra of isomeric 7-oxabicyclo[4.3.0]nonanes differ in the relative abundance of (M-H)+ ions. The critical energy of the angular hydrogen loss from the trans-annulated isomer 1 is lower by 9–10 kcal mol−1 than that of the cis-isomer 2, due to stereoelectronic assistance of the neighbouring oxygen pz orbital in the cleavage of the C(6)-H bond in 1XXX. High kinetic energy released during the hydrogen loss from 2XXX, [T] = 7.5 kcal mol−1, is consistent with non-relaxed geometry of the resulting (M-H)+ ion. Isomeric 2-oxabicyclo[4.4.0]decanes show analogous although smaller differences than 1 and 2. Photoelectron, electron impact, metastable and collision induced decomposition mass spectra are reported.

The mass spectra of the title compounds differ considerably depending on the annulation of the bicyclic skeleton. For a series of alkyl derivatives the cis-annulated compounds show a higher abundance of the products due to the retro Diels-Alder cleavage than the corresponding trans isomers. The cis-annulated esters and alcohols lose a molecule of ethanol and water, respectively, more easily than the corresponding trans isomers. Effects of conformation and configuration are discussed.

The Ziegler catalyst TiCl 4 -Et 2 AlCl and the arenetitanium(II) complex (η6-C 6 H 6 )Ti(II)(AlCl 4 ) 2 induce [6 + 2]cycloaddition reactions of cycloheptatriene with dienes and acetylenes. Addition to 1,3-butadiene affords 7 - endo - vinyl - bicyclo[4.2.1]nona - 2,4 - diene (main product) and bicyclo[4.4.1]- undeca - 2,4,8 - triene, a product of [6+4]cycloaddition. Isoprene reacts similarly, yielding mainly 7- endo - isopropenyl - bicyclo[4.2.1]nona - 2,4 - diene. 2,3 - Dimethyl - 1,3 - butadiene gives 8,9dimethylbicyclo [4.4.1]undeca - 2,4,8 - triene, a product of [6 + 4]cycloaddition, while [6 + 2]cross-adducts are minor products. The reaction of cycloheptatriene with norbornadiene gives mainly hexacyclo[6.5.1.0 2,7 .0 3,12 . 6,10 .0 9,13 ]tetradec - 4 - ene via [6+2]cycloaddition followed by intramolecular Diels-Alder reaction. As a by-product, pentacyclo[7.5.0.0 2,7 .0 3,5 .0 48 ]tetradeca - 10,12 - diene is formed by a [2+2+2]mechanism. Addition of cycloheptatriene to diphenylacetylene and bis - (tri- methylsilyl)acetylene furnishes sustituted bicyclo[4.2.1]nona - 2,4,7 - trienes. Alkenes, E,E -2,4 - hexadiene and 1,3 - cyclooctadiene are unreactive. The [6+2]cycloaddition is made possible by coordination of cycloheptatriene to titanium, which changes the symmetry of the frontier orbitals in the triene. The reactivity of the trienophile is also enhanced by coordination to the catalyst.

The fragmentation patterns of the title compounds are shown to depend on the nature of the ring annulation. On ionization the cis-annulated isomers lose a molecule of benzene in contrast to the corresponding trans isomers which do not. A mechanism involving a participation of the π-electron system in the cleavage of the 5-membered ring is suggested to explain the observed differences.

Dimerization of cycloheptatriene, catalyzed by titanium complexes, afforded pentacyclo[8.4.0.03,7.04,14.06,11]tetradeca-8,12-diene (I) (10%) and pentacyclo[7.5.0.02,8.05,14.07,11]tetradeca-3,12-diene (II) (90%). Structure of both dimers and their derivatives was determined by means of 1H NMR, 13C NMR and mass spectra. On heating, the diene II was converted into the more stable isomer I. On hydrogenation and further catalytic isomerization, both I and II gave diamantane in high yield.

Under electron impact cycloheptanol decomposes by four fragmentation paths: (1) α-cleavage with subsequent losses of C1-C5 fragments, (2) elimination of water, (3) loss of the hydrogen atom from C-1 and (4) loss of the hydroxyl group. The mechanism of water elimination was investigated by means of deuterium labelling. 1,4-Elimination of water predominates in cycloheptanol, with the stereospecific cis-1,3-elimination also being operative. The loss of water is preceded by extensive exchange of the hydroxyl hydrogen with those of the ring. This is attributed to a very facile transannular interaction of the hydroxyl group with the C-3 to C-6 positions that are made accessible due to conformational properties of the 7-membered ring. A kinetic model is proposed, describing migrations of the ring hydrogen atoms.

The paper describes syntheses of bicyclo[2.2.2]octan-1-ol, its 4-methyl and 4-phenyl derivatives, and bicyclo[2.2.2]octane-1,4-diol.

Fragmentation of ethyl(18-alkoxybicyclo[4.3.0]-3-nonene-7-carboxylates) was found to depend on the annulation of the rings. Following ionization, the cis-annulated isomers lose alcohol and benzene, while the trans-isomers fragment by other reaction paths. The regiospecificity of alcohol elimination from both the ester and the ether groups was determined by using deuterium-labelled analogues. A mechanism is discussed which rationalizes the differences observed in the spectra of the annulation isomers.

The TiCl4-(C2H5)2AlCl catalyst induced the Diels-Alder addition of bis(trimethylsilyl)acetylene to 1,3-cyclohexadiene affording 2,3-bis(trimethylsilyl)bicyclo[2.2.2]octa-2,5-diene in 72% yield under mild conditions. The product eliminates ethylene upon heating to 240 °C to give 1,2-bis(trimethylsilyl)benzene.

I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 11. Thermochemistry and kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 111. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 A. Orbital symmetry considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 B. Stereochemical approach . . . . . . . . . . . . . . . . . . . . . . 97 IV. Scope and limitations . . . . . . . . . . . . . . . . 101 A. Substituted cyclohexenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 B. Norbornene derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 C. Other bridged systems . . . . . . . . . . . . . . . . . . . . . . . . . 114 D. Ortho-condensed systems . . . . . . . . . . 117 E. Intramolecular RDA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 F. Heterocyclic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

Based on mass spectrometry, alkaloids of the rhoeadine type may be divided into acetals and semiacetals. Each series of compounds exhibits its own structurally characteristic fragmentation pattern.

The construction of a double beam mass spectrometer is described. A precision of 0.3 to 0.5% in the determination of the deuterium to hydrogen ratio was readily achieved by using a very high extraction voltage in the ion source. (auth)

Par chauffage des hydrazides d'acides salicylique et hydroxy-3 isonicotinique, synthese d'hexahydro-5,6,7,12,13,14 dibenzo [c,h] tetrazecine-1,2,6,7di-one-7,14 et d'hexahydro-5,6,7,12,13,14 dipyrido [3,4-c:3',4'-h] tetrazecine-1,2,6,7dione-5,12. Activite antituberculeuse

The structure of roemeridine, the major alkaloid from Roemeria hybrida was established by X-ray crystallography. Structure-significant features of the 1H and 13C NMR spectral mass spectral fragmentations are reported.

I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 11. Thermochemistry and kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 111. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 A. Orbital symmetry considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 B. Stereochemical approach . . . . . . . . . . . . . . . . . . . . . . 97 IV. Scope and limitations . . . . . . . . . . . . . . . . 101 A. Substituted cyclohexenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 B. Norbornene derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 C. Other bridged systems . . . . . . . . . . . . . . . . . . . . . . . . . 114 D. Ortho-condensed systems . . . . . . . . . . 117 E. Intramolecular RDA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 F. Heterocyclic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121