Six-membered Cyclic Compounds Research Articles

Direct addition of Zr-C bonds of alkylzirconocenes to activated alkenes.

Direct addition of alkylzirconocenes to activated alkenes was found, for the first time. Octyl- and decylzirconocene chloride reacted with benzylidenemalononitrile to give the corresponding addition products after hydrolysis in 86% and 79% yield, respectively. Zirconacyclopentanes showed a similar reactivity toward activated alkenes with a two-electron-withdrawing group. On the other hand, treatment of the reaction mixture of zirconacyclopentanes and ylidenemalononitriles with iodine afforded six-membered cyclic compounds in high yields. The diastereoselectivity of the cyclized compound was remarkably high and the high selectivity originated from the Zr-promoted cyclization. The structures of cyclic compounds 10b and the major diastereoisomer of 10d were determined by X-ray analysis. Zirconacyclopentenes reacted with ylidenemalononitrile with high chemoselectivity in which the sp(3)-carbon attached to zirconium reacted with ylidenemalononitrile.

Sphericity beyond Topicity in Characterizing Stereochemical Phenomena. Novel Concepts Based on Coset Representations and Their Subductions

Abstract Fundamental concepts proposed for comprehending stereochemical phenomena are described in order to bring out a more systematized format to conventional concepts and terminologies. The concept of coset representation (CR), the symbol of which is G(/Gi), is intuitively introduced by considering the global symmetry G and the local symmetry Gi for an orbit of stereochemically equivalent objects (e.g. atoms in a molecule). The SCR (set-of-coset-representations) notation for classifying molecular symmetries is proposed to remedy the usual insufficient classification based on point groups. According to the chirality/achirality of G and Gi, the sphericity concept (homospheric, enantiospheric, and hemispheric) and the relevant concept of chirality fittingness are proposed to specify the stereochemical phenomena of the G(/Gi)-orbit. The sphericity terms are shown to be superior to the well-known topicity terms (homotopic, enantiotopic, and heterotopic; chirotopic and achirotopic) especially in comprehending complicated stereochemical phenomena. In fact, the topicity terms as well as the terms “stereogenicity and prostereogenicity” and “prochirality” can be derived subsidiarily from the sphericity terms. The concept of subduction of CRs, for which the symbol G(/Gi) ↓ Gi has been coined, is proposed to characterize the desymmetrization of molecules. Thereby, the design of high-symmetry molecules is discussed in term of desymmetrization by atom replacement and by bond replacement. In order to characterize the stereochemistry of non-rigid molecules with rotatable ligands, the concept of proligand/promolecule is proposed; here biphenyl derivatives, methane derivatives, ethane derivatives, and ferrocene derivatives are examined in terms of matched and mismatched molecules. Applications to combinatorial enumeration, symmetry adapted functions, flexible six-membered cyclic compounds, and symmetry numbers are also described.

Design of a Novel Cyclopropane Donor Bis(trimethylsilylmethyl)cyclopropane and Its Electron Transfer Reactions

Abstract A novel donor of SET reactions, 1,1-bis(trimethylsilylmethyl)-2-phenylcyclopropane (BTCP), was designed to function as a homoallylic 1-phenyl-3-(trimethylsilylmethyl)-3-butenyl radical (5). Thus, non-irradiated reaction of BTCP with DDQ or chloranil gave a six-membered cyclic compound, which corresponds to a Diels–Alder adduct of 3-trimethylsilylmethyl-1,3-butadiene derived from BTCP. The photoinduced electron transfer reaction of BTCP with ketones afforded the C–C coupling products of 5 in high yields.

Unexpected results of enyne metathesis using a ruthenium complex containing an N-heterocyclic carbene ligand

Metathesis of enyne having 1,1-substituted alkene, carried out with the new generation of a ruthenium carbene complex containing an N-heterocyclic carbene ligand, gave five- and six-membered cyclic compounds in high yield.

Empirical relationship between structure and molecular optical rotation in six-membered cyclic compounds

The molecular optical rotation of a six-membered series of cyclic compounds has been calculated with a simple method which relates the sign and magnitude of the molecular optical rotation to the geometry, conformation and absolute configuration of the studied compounds. The optimised geometry of each conformer was calculated by molecular mechanics calculations. The values obtained seem to confirm the existence of a close relationship between the value of molecular optical rotation of a compound and its geometry.

Asymmetric cyclization of meso-diepoxides using chiral (salen)Co(III)OAc catalyst forming optically active 1,4-anhydropentitols and 2,5-anhydrohexitols

The asymmetric hydrations of meso-diepoxides, 1,2:4,5-dianhydro-3- O-methylxylitol 2, 1,2:5,6-dianhydro-3,4-di- O-methylallitol 3 and 1,2:5,6-dianhydro-3,4-di- O-methylgalactitol 4, were carried out using ( R, R)- 1 and ( S, S)- 1. An optically active five-membered cyclic compound was selectively produced in good yield from 2, but a mixture of the five- and six-membered cyclic compounds was obtained in the cases of 3 and 4. The ees of all cyclic products exceeded 90%.

Sequence of Reactant Combination Alters the Course of the Staudinger Reaction of Azides with Acyl Derivatives. Bimanes. 30.

The Staudinger reaction of azides has now been followed by NMR and other spectroscopic techniques. syn-(Azidomethyl,methyl)(methyl,methyl)bimane (1) and Ph(3)P form a triazaphosphadiene intermediate 2 and then the bimane P-triphenyliminophosphorane 3. The iminophosphorane reacts with an acyl chloride to yield an iminophosphonium salt 4 which then forms the oxazaphosphetane 13. The latter undergoes an electrocyclic reversion to form the phosphine oxide and the chloroimines 7E and 7Z, the last being hydrolyzed to the (acylamido)bimane 6. This set of reactions constitutes the "iminophosphorane pathway". A significant diversion of the reaction path to an (N-alkylamino)phosphonium chloride 8 occurs through reaction of 4 with H(2)O present in the CDCl(3) and through reaction of 3 with HCl. A different azide (alpha-azido-o-xylene 1b) produces the (acylamido)-o-xylene as the sole product. A less sterically hindered phosphine (tri-2-furylphosphine) reacts more slowly to form the iminophosphorane 3a from the azidobimane 1. Reaction of the bimane P-tri-2-furyliminophosphorane with acyl chloride gives only the (acylamido)bimane 6. If the acyl chloride is mixed with 1, followed by addition of the Ph(3)P, the triazaphosphadiene adduct 5 is formed via the triazaphosphadiene. The adduct 5 is converted rapidly into a six-membered cyclic compound 11. The latter either loses nitrogen to yield 6 via 7Z and 7E and the phosphine oxide or loses chloride 10 through a novel chloride-induced elimination reaction from its protonated form. The change in procedure thus results in a dramatic change in the reaction pathway, a reaction set that constitutes the "triazaphosphadiene adduct pathway". In the case of alpha-azido-o-xylene, alpha-chloro-o-xylene (10b) is the only product. The reactions of the azides 1 or 1b with tri-2-furylphosphine also produce chlorides as the major products accompanied by some acetamido derivatives. The nucleophile-induced reaction explains a "surprising result" (formation of ester rather than amide) reported by Sahlberg et al. (Sahlberg, C.; Jackson, A. M.; Claesson, A. Acta Chem. Scand. 1988, B42, 556-562). The intramolecular "aza-Wittig" reaction may depend on the nucleophilicity of the triazaphosphadiene. A comprehensive mechanistic scheme for the Staudinger reaction of azides is conveniently divided into the following: (A) formation of the triazaphosphadiene (Scheme 1), (B) reactions of the triazaphosphadiene (Scheme 2), and (C) reactions via the iminophosphorane (Scheme 3). Some approximate kinetic parameters are reported for some of the reactions.

A Possible Explanation for Preferential Stabilization of the Substituent Axial Conformation in Alkoxy- or Siloxy-substituted Six-membered Cyclic Compounds by the s Æ s* Orbital Overlap: Remarkable Effect of Electron-withdrawing Groups

A Possible Explanation for Preferential Stabilization of the Substituent Axial Conformation in Alkoxy- or Siloxy-substituted Six-membered Cyclic Compounds by the s Æ s* Orbital Overlap: Remarkable Effect of Electron-withdrawing Groups

Cyclohydrosilylation dimer formation: evidence for Pt 0 Pt II Pt IV catalysis

An eight-membered cyclic compound, 2,2,3,4,4,6,6,7,8,8-decamethyl-1,5-dioxa-2,4-disilacyclooctane ( VIII), along with the expected five-membered 2,2,5,5-tetramethyl-1-oxa-2-silacyclopentane ( V) were found to be the major products when vinyldimethylcarbinoxydimethylsilane ( I) ( i.e. 2-methyl-3-buten-2-oxydimethylsilane) was subjected to cyclohydrosilylation using platinum catalysis. The eight-membered product ( VIII) readily undergoes β-elimination during gas chromatography (GC) analysis to extrude 2-methyl-2-butene giving the six-membered 2,2,4,4,5,6,6-heptamethyl-1,3-dioxa-2,4-disilacyclohexane ( VI). Contrary to an earlier report (T.H. Lane and C.L. Frye, J. Organomet. Chem., 172 (1979) 213), no siloxetane or silanone intermediates are needed to rationalize the formation of the six-membered cyclic compound. When (Wilkinson's) rhodium catalyst was used for the hydrosilylation, only V was formed. The formation of VIII with platinum catalysis is rationalized by a mechanism utilizing successive oxidative additions to both Pt 0 and Pt II catalytic species; i.e. the absence of a second catalytically active level of rhodium is believed responsible for its inability to yield the eight-membered cyclic. Similarly, dimerization of either 1,1-dimethyl-1-silacyclobutane or 1,1,3,3-tetramethyl-1,3-disilacyclobutane to form the cyclooctanes can be readily achieved by platinum catalysis but not by rhodium catalysis. These results constitute the first examples of processes believed to require the presence of not only one but two catalytically active oxidation levels.

Radical Cyclization of Mesitylsulfonylhydrazones

Radical cyclization of mesitylsulfonylhydrazones provides a useful method for the formation of unsubstituted five- and six-membered cyclic compounds. Thus, diethyl 3-methyl-3-cyclopentene-1,1-dicarboxylate (2) was formed by reaction of diethyl 5-bromo-1-mesitylsulfonylhydrazono-5-hexene-3,3-dicarboxylate (1b) with tributyltin hydride and 2,2′-azobisisobutyronitrile in benzene.

Axial Preference of Bulky Group- and Electron-Withdrawing Group-Substituted Oxygen Atom on the Chair-Type -Cyclohexanone, -Glutaric Anhydride, and -Glutarimide

Abstract Axial preference (>ca. 70% at 25 °C) of alkoxy and silyloxy groups of the chair-type six-membered cyclic compounds has been clarified by the 1H-NMR bandwidth mesurement method. Based on the X-ray analysis of 4-substituted cyclohexanones, it has been disclosed that the cyclohexanone ring adopts chair form and the 4-substituent occupies the axial site in all cases.

Free-Radical Approach to C–C Bond Formation on a Trifluoromethyl-Substituted Carbon. Intramolecular Cyclization

Abstract A trifluoromethyl-substituted carbon radical, generated by radical deoxygenation of α-trifluoromethyl alcohol, intramolecularly formed C–C bond to give a five- or six-membered cyclic compound.

Reaction of Tri-n-butyltin ω-Haloalkoxide (n-Bu3SnO(CH2)nX) with Isothiocyanate

Abstract Tri-n-butyltin ω-haloalkoxides are useful reagents for the preparation of sulfur-containing five and six-membered cyclic compounds combined with isothiocyanates.

A new strategy to sulfur heterocycles: Reactions of an allene episulfide with electrophiles

A variety of sulfur-containing five- and six-membered cyclic compounds was obtained by the acid-catalyzed and thermal reactions of an allene episulfide with various electrophiles.

Tellurium NaX zeolites: I. Deuterium tracer studies of cyclohexane dehydrogenation to benzene

Deuterium tracers were used to explore the mechanisms of dehydrogenation of six-membered cyclic compounds to benzene over a Te NaX zeolite catalyst. Dehydrogenation of cyclohexane to cyclohexene (and probably to cyclohexadiene) precedes the formation of benzene. A large primary kinetic isotope effect ( k c 6h 12 k c 6D 12 ~ 2.5 at 400 ° C ) indicates that cleavage of the CH bonds in cyclohexane is the rate-determining reaction step. Although the presence of gaseous hydrogen is required to maintain catalyst activity, the dehydrogenation rates are the same in H 2 as they are in D 2. Only a limited amount of exchange occurs between D 2 and H atoms in the hydrocarbons. The exchange which is observed probably arises from double bond shift that occurs in the olefins by an addition/abstraction mechanism on a single Te atom containing one adsorbed D atom. Cyclohexane can be formed from cyclohexene by hydrogen transfer from another cyclohexene molecule much more readily than it can be formed by direct saturation with gaseous H 2. Both the dehydrogenation and isomerization sites are probably Te 0 surface atoms.

Metal-catalyzed organic photoreactions. TiCl4-catalyzed photoreaction of 2-acetyl-1,3-dicarbonyl compounds in methanol

When five- and six-membered cyclic β-dicarbonyl compounds having an acetyl group on the 2-position were irradiated in methanol in the presence of TiCl4, a coupling reaction between the acetyl carbonyl atom and the α-carbon atom of the methanol took place, giving γ-ketoaldehydes or dihydrofurans as the main product.

Organoboron compounds. 348. N-dialkylborylamidines from N,N'-disubstituted amidines

1. Dialkylborylamidines, which have a chelate structure or are equilibrium mixtures of a chelate and an open form, have been synthesized from N,N'-disubstituted amidines. 2. N-Dialkylboryl-N,N'-disubstituted amidines are capable of adding to the multiple bonds of aldehydes and isocyanates to form the corresponding six-membered cyclic coordination compounds of boron.

Thermochemistry of some six-membered cyclic and polycyclic compounds related to coal

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThermochemistry of some six-membered cyclic and polycyclic compounds related to coalRobert Shaw, David M. Golden, and Sidney W. BensonCite this: J. Phys. Chem. 1977, 81, 18, 1716–1729Publication Date (Print):September 1, 1977Publication History Published online1 May 2002Published inissue 1 September 1977https://doi.org/10.1021/j100533a004RIGHTS & PERMISSIONSArticle Views203Altmetric-Citations50LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts

Synthesis of six-membered cyclic compounds, containing the carbon atoms of the o-carborane nucleus and one heteroatom in the ring

Bis-(o-carboranyl)methoxymethane was synthesized from monolithium-o-carborane and 1,1-dichloro-methyl methyl ether, from which were obtained six-membered carborane heterocycles that contain an aliphatic carbon atom, the four carbon atoms of two o-carborane nuclei, and one heteratom (Si, Sn, Ge, P, and As) in the ring.

Rigidity to carbanion inversion of four-, five, six-membered cyclic organomagnesium compounds

Rigidity to carbanion inversion of four-, five, six-membered cyclic organomagnesium compounds