Search results for "Isocyanate"
showing 10 items of 47 documents
The Reaction of 4-Amino-2-oxazolines with Isocyanates and Isothiocyanates. Synthesis and X-Ray Structures of Polysubstituted 2-Imidazolidinones, 1,3-…
2006
Abstract Reactions of 4-alkylamino-2-phenyl-2-oxazolines 1 with isocyanates and isothiocyanates provide unprecedented efficient and regioselective heterocycle–heterocycle transformations. Compounds 1 reacted rapidly with tosyl isocyanate yielding directly 3-alkyl-4-benzamido-1-tosyl-2-imidazolidinones 4 in almost quantitative yields. The corresponding ureido intermediates 2 were not isolable species. However, the reactions with non-sulfonylated isocyanates or isothiocyanates were slower, leading to the expected ureido and thioureido derivatives 5, which were easily and efficiently transformed to either polysubstituted 2-imino-1,3-oxazolidine or 2-imino-1,3-thiazolidine hydrochlorides 7, res…
III. Darstellung und molekülstruktur von triazoboracyclooctanen
1976
Abstract The aminoboration of phenylisocyanate or phenylisothiocyanate with 2-phenyl-1,3,2-diazabora-cyclohexane yields under ring expansion the eight-membered BNC-heterocycles 2,3-diphenyl-1,3,5-triaza-2-bora-cyclooctane-4-one or 2,3-diphenyl-1,3,5-triaza-2-bora-cyclooctane-4-thione, respectively. Isomeric structures, which can appear in the insertion reaction, are discussed on the basis of spectroscopic data.
Darstellung eines neuen achtgliedrigen BNC-heteroringes
1975
Abstract 2-Phenyl-1,3,2-diazaboracyclohexane reacts with phenylisocyanate by an insertion reaction leading to an eight-membered BNC-heterocycle.
Imidotungsten(VI) complexes with chelating amino and imino phenolates
2011
The reaction of WOCl(4) with 2,4-di-tert-butyl-6-((isopropylamino)methyl)phenol followed by the reaction with phenyl isocyanate leads to the formation of imidotungsten(VI) complex [W(NPh)Cl(3)(OC(6)H(3)(CH(2)NH-i-Pr)-2-t-Bu(2)-4,6)] 4 with a chelating aminophenolate ligand. When the same procedure was applied using aminophenols with bulkier substituents in the amino group, the final product was an unexpected Schiff-base complex [W(NPh)Cl(3)(OC(6)H(3)(CH=NPh)-2-t-Bu(2)-4,6)] 5, where the ligand is derived from 2,4-di-tert-butyl-6-((phenylimino)methyl)phenol. Complex 5 is also formed in the thermal degradation of 4. On the whole, 5 appears to be formed by a disproportionation of intermediate …
Permanent stenting in “unextractable” common bile duct stones in high risk patients. A prospective randomized study comparing two different stents
2007
BACKGROUND: Endoscopic sphincterotomy (ES) and stone extraction is the treatment of choice for bile duct stones. Therefore, if ES and conventional stone extraction fail, further treatment is mandatory. Insertion of a biliary endoprosthesis is an effective option. MATERIALS AND METHODS: We treated 30 high-risk patients (17 women and 13 men, mean age 82 years) affected by difficult common bile duct stones. The patients were randomly assigned preoperatively using closed envelopes (blind randomization) into two groups to receive insertion of polyethylene or hydrophilic hydromer-coated polyurethane stent, respectively. Follow-up was achieved by contacting referring physicians and patient's relat…
Thioether-Bearing Hyperbranched Polyether Polyols with Methionine-Like Side-Chains: A Versatile Platform for Orthogonal Functionalization
2016
The synthesis of thioether-bearing hyperbranched polyether polyols based on an AB/AB2 type copolymerization (cyclic latent monomers) is introduced. The polymers are prepared by anionic ring-opening multibranching copolymerization of glycidol and 2-(methylthio)ethyl glycidyl ether (MTEGE), which is conveniently accessible in a single etherification step. Slow monomer addition provides control over molecular weights. Moderate dispersities (Đ = 1.48–1.85) are obtained, given the hyperbranched structure. In situ 1H NMR copolymerization kinetics reveal reactivity ratios of rG = 3.7 and rMTEGE = 0.27. Using slow monomer addition, copolymer composition can be systematically varied, allowing for th…
TG/DTA-FTIR as a method for analysis of tall oil based rigid polyurethane foam decomposition gaseous products in a low oxygen environment
2020
Abstract This study is an investigation of the suitability of the thermogravimetry and differential thermal analysis method coupled with Fourier Transform Infrared spectrometry (TG/DTA-FTIR) for a thermal degradation gaseous product analysis of a rigid polyurethane-polyisocyanurate (PU-PIR) foam synthesised from high functionality tall oil fatty acids (TOFA) based polyols. The FTIR spectra of the TG-generated gaseous thermal degradation products of three PU-PIR formulations with varied high functionality TO based polyol content (45, 75 and 95 pbw) and a different tier of isocyanate (NCO) indexes (110, 150, 200, 300 and 400) for each formulation were compared to the spectra of a formulation …
A Versatile Synthesis of Fluorinated Uracils in Solution and on Solid-Phase.
2004
[reaction: see text] An efficient and convenient two-step synthesis of new fluorinated uracils is described. The first step involves the condensation of an ester enolate with a fluorinated nitrile to furnish fluorinated beta-enamino esters. In turn, these compounds react with organic isocyanates or isothiocyanates to give C-6 fluorinated uracils or thiouracils, respectively, in excellent yields. This synthesis has been successfully adapted to solid-phase conditions with high diversity, thereby facilitating the creation of small (thio)uracil libraries.
Pyrrolo[2,1-d][1,2,3,5]tetrazine-4(3H)-ones, a new class of azolotetrazines with potent antitumor activity.
2003
Pyrrolo[2,1-d][1,2,3,5]tetrazinones 10a-o, compounds that hold the deaza skeleton of the antitumor drug temozolomide, were prepared by reaction of 2-diazopyrroles 9 and isocyanates. Such a synthetic route represents, among those leading to azolotetrazinones reported so far, the only possible one since attempts to cyclize to the title ring system 2-amino-1-carbamoylpyrroles 11 or the mono substituted 2-triazenopyrrole 12 failed. Compounds 10 were screened at the National Cancer Institute (NCI) for their activity against a panel of about 60 human tumor cell lines. Most of them possess remarkable antineoplastic activity having GI(50) values in the low micromolar or sub-micromolar range and rea…
Homochiral oxazolidin-2-ones and imidazolidin-2-ones by tandem nucleophilic addition–conjugate addition
2004
Abstract Treatment of both primary alcohols 1a , b and secondary amines 1c , d , tethered to a Michael acceptor with ( R )-phenylethyl isocyanate in the presence of DBU gave in good yield and high stereoselection diastereomeric mixtures of oxazolidin-2-ones 2a , b and 3a , b and imidazolidin-2-ones 2c , d and 3c , d , respectively. The cyclisation reaction was studied computationally by ab initio quantum mechanical methods. The observed stereoselectivity was explained on the basis of the different stability of both anions and transition states leading to 2a and 3a , respectively. The usefulness of the method was proven by conversion of 2a into the enantiomerically pure bioactive amino acid …