Double Ring Opening Research Articles

Organolithium‐Induced Synthesis of Acyclic Unsaturated Amino Alcohols from Epoxides of Dihydropyrroles and Tetrahydropyridines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Organolithium-induced synthesis of acyclic unsaturated amino alcohols from epoxides of dihydropyrroles and tetrahydropyridines

The alkylative double ring-opening of Bus-protected 2,5-dihydropyrrole epoxides 13 and 29 with organolithiums to give 3-substituted 1-aminobut-3-en-2-ols 13– 19 and 30– 32 are described. Bus-protected tetrahydropyridine epoxide 38 reacts with organolithiums to give 4-substituted 1-aminobut-4-en-3-ols 39 and tetrahydropyridinol 40 .

Enantioselective Alkylative Double Ring-Opening of Epoxides Derived from Cyclic Allylic Ethers: Synthesis of Enantioenriched Unsaturated Diols.

For Abstract see ChemInform Abstract in Full Text.

Enantioselective Alkylative Double Ring Opening of Epoxides: Synthesis of Enantioenriched Unsaturated Diols and Amino Alcohols.

Enantioselective Alkylative Double Ring Opening of Epoxides: Synthesis of Enantioenriched Unsaturated Diols and Amino Alcohols.

Enantioselective alkylative double ring-opening of epoxides derived from cyclic allylic ethers: synthesis of enantioenriched unsaturated diolsElectronic supplementary information (ESI) available: the preparation and characterisation of derivatives for ee determinations. See http://www.rsc.org/suppdata/ob/b2/b212404a/

A screen of external chiral ligands has led to enantioselective organolithium-induced alkylative double ring-opening of 3,4-epoxytetrahydrofuran 1 with n-BuLi to give 3-methyleneheptane-1,2-diol 3 in 75% yield and 55% ee in the presence of bisoxazoline 10, and in up to 60% ee in the presence of (-)-sparteine 2. Extending the alkylative double ring-opening reaction to epoxides derived from oxabicyclo[n.2.1]alkenes (n = 2.3) results in the formation of cycloalkenediols, which, when carried out in the presence of (-)-sparteine 2 affords products in up to 85% ee.

Enantioselective Alkylative Double Ring Opening of Epoxides: Synthesis of Enantioenriched Unsaturated Diols and Amino Alcohols

Enantioselective Alkylative Double Ring Opening of Epoxides: Synthesis of Enantioenriched Unsaturated Diols and Amino Alcohols

Enantioselective Alkylative Double Ring Opening of Epoxides: Synthesis of Enantioenriched Unsaturated Diols and Amino Alcohols

Enantioselective Alkylative Double Ring Opening of Epoxides: Synthesis of Enantioenriched Unsaturated Diols and Amino Alcohols

Enantioselective alkylative double ring opening of epoxides: synthesis of enantioenriched unsaturated diols and amino alcohols.

Enantioselective generation and intermolecular trapping of a lithium carbenoid occurs in the reaction of epoxides of 2,5-dihydrofuran, 2,5-dihydropyrrole, and oxa- and aza-bicyclo[n.2.1]alkenes (n=2, 3) with organolithium compounds in the presence of external chiral ligands. This methodology leads to the synthesis of important unsaturated diol and amino alcohol functionality (see scheme; tert-butoxycarbonyl).

ChemInform Abstract: Substituted Alkenediols by Alkylative Double Ring Opening of Dihydrofuran and Dihydropyran Epoxides.

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Solvent-mediated selective single and double ring-opening of N-tosyl-activated aziridines using benzylamine

An efficient methodology has been developed for the synthesis of a series of new diamine 2 and triamine ligands 3 for application in asymmetric catalysis via selective single or double ring-opening of tosylaziridines 1, which are derived from chiral pool amino acids. The selectivity of the ring-opening reaction is readily controlled by the solvent employed. Thus, in acetonitrile formation of secondary amines 2 occurs via a single ring-opening step, whilst in methanol the reactions proceed to give the tertiary amines 3 via the ring-opening of two aziridine molecules.

Unsaturated 1,2-Amino Alcohols from Dihydropyrrole Epoxides and Organolithiums

The alkylative double ring-opening of Bus-protected 2,5-dihydropyrrole epoxide 11 with organolithiums to give 3-substituted 1-aminobut-3-en-2-ols 13-19 is described.

Substituted alkenediols by alkylative double ring opening of dihydrofuran and dihydropyran epoxides.

[reaction: see text]. Dihydrofuran and dihydropyran epoxides undergo alkylative double ring opening with organolithiums to provide a new route to substituted alkenediols.

Synthesis and structural characterization of (4,7-dioxaoctyl)phenyldichlorostannane and triphenyltin compounds containing various polyoxaalkyl moieties

The synthesis and characterization of (4,7-dioxaoctyl)triphenyltin ( 1), (4,7,10-trioxaundecyl)triphenyltin ( 2), (4,7,10,13-tetraoxatetradecyl)triphenyltin ( 3), and (4,7-dioxaoctyl)phenyldichlorostannane ( 4) are reported. Investigatons using 1H-, 13C-, and 119Sn-NMR, gradient assisted 2D 1H– 13C HMBC and HMQC NMR, 1D 1H– 119Sn HMQC NMR demonstrate that 1– 3 are essentially tetracoordinated. By contrast, the structure of compound 4, determined by X-ray diffraction methods, reveals a hexacoordinated, distorted octahedral geometry, in which the 4,7-dioxaoctyl ligand is tridentate, with a facial arrangement of the C, O, O atoms with respect to tin. NMR investigations reveal that this structure exists in solution, but is labilized by a double ring opening–closing mechanism.

Substituent Effect on the Cationic Monomer-Isomerization Polymerization of (Cyclic Imide)-Substituted Oxetanes with Two Different Ring-Opening Routes

This study reports the effect of substituent on the cationic monomer-isomerization ring-opening polymerization of 3-(R 1 -methyl)-substituted 3-R 2 -oxetanes (1), in which R 1 is phthalimide, maleimide, succinimide, or glutarimide and R 2 is ethyl, benzyl, phenyl, or isopropyl. The acid-catalyzed polymerization of 1 gave polyacetal (3) or polyether (4), together with an isomeric bicyclic acetal (2). The isomerization of 1 to 2 took place prior to polymerization. Subsequently the polymerization of 2 occured by either single or double ring opening depending on temperature. The polymerization mechanism is discussed in detail based on the coordination of 1 to Lewis acid and the substituent effect on the polymerization manner. In the double ring-opening polymerization of 2 at 130°c, a carbon-carbon double bond of the lactam ring was indispensable for stabilizing the carboxonium-propagating end. Therefore, 2 carrying a saturated lactam ring did not polymerize in such a manner. Phenyl-substitued oxetane phthalimide was unique in undergoing an unusual cyclodimerization at 130°C, primarily because of the high susceptibility of the neophyl-type carbon skeleton to a cation transfer. On the other hand, most 2 brought about the single ring-opening polymerization below room temperature, regardless of the lactam substituent and the R 2 group. This polymerization was an equilibrium polymerization through a bicyclic oxonium-propragating end, and the thermodynamic parameters of polymerization were determined. Thus, 3 was transformed into 4 in one pot, by a combination of the depolymerization of 3 and the repolymerization of 2 above the ceiling temperature. From the structure analysis of 2 it was inferred that the single ring-opening polymerizability arises from dipole-dipole repulsion between the parallel standing lone pairs of two acetalic oxygen atoms in a nearly symmetric bicycle. There fore, 2 having a somewhat twisted bicyle showed no single ring-opening polymerizability.

Synthesis and Cationic Polymerization of 2-Phenyl-1,6-dioxaspiro[4.6]undecane. A Novel Expandable Monomer Undergoing Cationic Double Ring-Opening Polymerization

Synthesis and Cationic Polymerization of 2-Phenyl-1,6-dioxaspiro[4.6]undecane. A Novel Expandable Monomer Undergoing Cationic Double Ring-Opening Polymerization

The double ring-opening polymerization of sulfur containing spiro orthocarbonates

The polymerization of new sulfur containing spiro orthocarbonates with the ability to undergo double ring-opening is reported. Various initiators were used in the cationic polymerization study, and the polymer structure determined. The polymerization is proposed to occur via a controlled tandem double ring-opening mechanism.

Double Ring-Opening Reactions of Bis-Cyclopropanes Promoted by Iron Salts

Double Ring-Opening Reactions of <i>Bis</i>-Cyclopropanes Promoted by Iron Salts

Sulfur Analog of Spirocyclic Orthocarbonate Capable of Undergoing Tandem Double Ring-Opening Polymerization: Synthesis, Structure, and Cationic Polymerization of Dibenzo[3,4;10,11]-1,6,8,13-tetrathiaspiro[6.6]tridecane, Property of the Polymer, and Volume Change on Polymerization

The sulfur analog of spiroorthocarbonate (SOC) capable of undergoing tandem double ring-opening polymerization (dibenzo[3,4;10,11]-1,6,8,13-tetrathiaspiro[6.6]tridecane, 4) was synthesized, and its polymerization behavior was studied. Some properties of the polymers obtained and the volume change on polymerization of 4 were also examined. The synthesis of 4 was performed by the acid-catalyzed ester-exchange reaction of tetrakis(methylthio)methane with o-xylenedithiol and was obtained in 98% yield. The structure of 4 was determined by the spectral and elemental analysis data. Cationic polymerization of 4 with latent thermal initiator benzyl tetrahydrothiophenium hexafluoroantimonate in nitrobenzene proceeded efficiently at more than 150 °C to give the corresponding poly(thioethertrithiocarbonate) 5. The polymer structure was determined by the spectral data and further confirmed by the structures of the decomposition products formed by the reductive cleavage of the trithiocarbonate bond of with LiA1H 4 . The mechanism of the polymerization was postulated from the results obtained. Thermal properties of such as T g and T m were examined and compared with those of its oxygen analog (13). The volume change was studied in the polymerizations of4 and its oxygen analog (2), during which 5.2 and 6.7% volume expansions were observed, respectively.

Syntheses and radical ring-opening polymerization behavior of vinylcyclopropanone cyclic acetals having exomethylene and phenyl groups

Syntheses and radical ring-opening polymerizations of vinylcyclopropanone derivertives having cyclic six-membered acetal, exomethylene, and phenyl groups; 1-vinyl-6-methylene-4,8-dioxaspiro [2.51 octane (2b), 1-vinyl-5,7-dimethyl-6-methylene-4,8-dioxaspiro[2.5]octane (2c), 1-vinyl-5-phenyl-4,8-dioxaspiro [2.5] octane (2d), and 1-vinyl-5,7-diphenyl-4,8.dioxaspiro12.sloctane (2e), were carried out. The monomers were prepared by reactions of l,l-dichloro-2-vinylcyclopropane and the corresponding diols in DMF in the presence of sodium hydride. Radical polymerizations of 2b-2e were carried out at 60, 80, and 120°C in the presence of an appropriate initiator (3 mol % vs. monomer) in degassed sealed ampoules for 20 h. Although colorless transparent polymers (M n 2300 - 13,500) were isolated by preparative HPLC for the most monomers, a crosslinked polymer was obtained in the case of 2b. The structures of the polymers were determined to consist of single and double ring-opening units. The content of the double ring-opened unit was 25-75% by comparison of IR spectra to a model compound. It is suggested that the double ring-opened propagating chain end is stabilized by the substituents on the cyclic acetal rings. The two-center energies of the cyclopropane ring and activation energy of ring-opening calculated by molecular orbital methods may explain the selectivity in the cleavage of the cyclopropane ring, and the degree of double ring-opening.

Synthesis and Photoinitiated Cationic Polymerization of 2-Methylene-7-phenyl-1,4,6,9-tetraoxaspiro[4.4]nonane

Synthesis of the asymmetrically substituted 2-methylene-7-phenyl-1,4,6,9-tetraoxaspiro[4.4]nonane monomer in four steps and its polymerization are described. The spiromonomer is liquid at room temperature. Photoinitiated cationic polymerization of 2-methylene-7-phenyl-1,4,6,9-tetraoxaspiro[4.4]nonane at ambient temperature in bulk was investigated, using a cationic photoinitiator system based on (η5-2,4-cyclopentadiene-1-yl)[1,2,3,4,5,6-η](1-(methylethyl)benzene)iron(I) hexafluorophosphate (Irgacure 261). Upon irradiation, within 10 min quantitative double ring-opening polymerization to a structurally well-defined poly(alkylene−carbonate−ketone) with molecular weight average Mw of 27.000 (GPC) occurred. No elimination, vinylidene polymerization, or single ring-opening polymerization was detected, as commonly observed in the case of free-radical initiation of similar spiroorthocarbonates, spiroorthoesters, or methylenedioxolanes were detected. Despite quantitative double ring opening, no volume expansion occurred during polymerization. A volume shrinkage of 4.1% was found. General structural prerequisites for expanding and pseudoexpanding monomer systems are discussed.