Synthesis of isocyanates and carbodiimides

The reaction of 1,3-disubstituted ureas and 1-arylsulfonyl-3-alkylureas with phosgene permits the preparation of a number of isocyanates and sulfonyl isocyanates that had not previously been described, or that were difficult to prepare. 1,3-Disubstituted thioureas and 1-aryl-(or alkyl)sulfonyl-3-alkylthioureas give carbodiimides. Thionyl chloride and phosphorus pentachloride react with the urea derivatives in the same way as phosgene. Oxalyl chloride reacts with ureas to form parabanic acid derivatives, whereas with thiourea it gives 2-imino-1,3-thiazolidine-4,5-diones, which can isomerize to parabanic acid derivatives.     

光气法制备酰氯的催化剂研究进展

酰氯是一类用途非常广泛的重要有机合成中间体,在工业上制备酰氯主要使用的氯化剂包括PCl3、PCl5、SOCl2、光气等,充分反应后通过过滤、蒸馏等工艺进行脱色提纯制得酰氯。光气法由于对环境污染较低,是目前最常用的方法。三光气可以分解成光气,其优良的物理、化学性质以及便捷的储存和运输条件是光气的最佳替代化学品。但由于光气活性较低,在使用过程中添加催化剂必不可少,本文将重点介绍目前光气法制备酰氯时所使用的各种催化剂及其性能。     

A highly selective and sensitive fluorescence "turn-on" probe for Ag+ in aqueous solution and live cells

A naphthalimide-based fluorescent probe, NPQ, that contains a novel receptor was successfully developed. NPQ exhibited "turn-on" fluorescence and excellent selectivity toward Ag(+) in the presence of various other metal ions in aqueous solution. A series of control compounds were designed and synthesized in order to explore the photoinduced electron transfer (PET) quenching mechanism of NPQ and binding mode of NPQ with Ag(+). Moreover, with the NPQ-Ag(+) complex, I(-) was easily selectively recognized by a marked fluorescence quenching. The live cell imaging experiments demonstrate that NPQ can be used as a fluorescent probe for monitoring Ag(+) in living cells.     

The reaction of indole and the indole grignard reagent with phosgene. A facile synthesis of indole-3-carboxylic acid derivatives

Indole-3-carboxylic acid (as well as indole-3-glyoxylic acid) derivatives are readily prepared from indoles (including oxindoles) and phosgene (oxalyl chloride), respectively. The interaction of these reagents with the indole Grignard reagent afforded several products including the cyclo-tetramers, 21 and 30 . Indolo-fused heterocycles can be readily prepared from the reaction of phosgene (or oxalyl chloride) with suitable reactants. Thus e.g., phosgene and 2-(2-hydroxy-phenyl)-N-methylindole readily gave 5,6-dihydro-11-methyl-6-oxobenzo[a]pyrano[4,3-b] indole ( 33 ).     

A highly selective colorimetric and ratiometric two-photon fluorescent probe for fluoride ion detection

A naphthalimide-based highly selective colorimetric and ratiometric fluorescent probe for the fluoride ion displayed both one- and two-photon ratiometric changes. Upon reaction with the F(-) (TBA(+) and Na(+) salts) anion in CH(3)CN as well as in aqueous buffer solution, probe 1 shows dramatic color changes from colorless to jade-green and remarkable ratiometric fluorescence enhancements signals. These properties are mechanistically ascribed to a fluoride-triggered Si-O bond cleavage that resulted in a green fluorescent 4-amino-1,8-naphthalimide.     

Combustion and Toxicity: Discussion

Dr. Shakoor (Republic of Iraq): I have read that some phosgene is liberated through the burning of polyvinyl chloride). Is this true, and, if so, how can it be explained?     

Products of the reaction of anabasine with phosgene

Chemistry of Natural Compounds - The reaction of anabasine with phosgene has given the anabasinium salt of phosgene, anabasine-N-carbonyl chloride, and the urea derivative...     

Continuous in situ generation and reaction of phosgene in a microflow system

Continuous in situ generation of phosgene and its use in acid chloride formation in a microflow system were demonstrated. The acid chloride was subsequently coupled with an amine in high yield without severe epimerization.     

基于萘酰亚胺的次氯酸荧光探针的合成及细胞成像性能研究

以萘酰亚胺结构为荧光发色团,设计开发了一种含C=C双键的、具有分子内电荷转移(ICT)效应的新型水溶性优化的次氯酸荧光探针3-(2-氰基丙烯酸乙酯基)-4-羟基-N-正丙基-1,8-萘酰亚胺(NAEC).添加次氯酸后,探针分子NAEC中的C=C双键被氧化,生成醛基,探针NAEC原有的ICT效应被破坏,产生荧光信号.经核磁、质谱、荧光发射光谱和UV-Vis吸收光谱对其结构和检测性能进行了研究.结果表明,在pH=7.4的N,N-二甲基甲酰胺(DMF)/磷酸缓冲盐溶液(PBS)(V∶V=1∶19)缓冲体系中,探针NAEC可在10s内完成对次氯酸的检测,荧光分析检测限为2.4nmol/L,斯托克斯位移为100nm;探针NAEC显示出较强的抗干扰性,能在其他活性氧、小分子生物硫醇及常见阴离子等22种干扰物存在下完成次氯酸的专一检测.同时,该探针分子的膜透性与生物相容性良好,具备较好的活体内源性ClO-荧光成像能力,在生物检测及环境监控等领域具有良好的应用前景.     

1-(Aziridine) carbonyl chlorides and 1-(aziridine) carbonyl quaternary ammonium chlorides. Rearrangement to 2-(chloroalkyl) isocyanates

Aziridine reacted with phosgene in the presence of an acid acceptor or with 1,1′-carbonylbis(pyridinium) chloride to produce 1-(aziridine)carbonyl chloride (XII) or 1-(aziridine)carbonyl pyridinium chloride (XIII), respectively, as transient intermediates. Attempts to trap and observe (XII) and (XIII) at -10° were unsuccessful. These elusive materials underwent facile rearrangements to 2 - chloroethyl isocyanate under these conditions. Aziridine reacted with 1,1′-carbonylbis(triethylammonium)chloride (VII) at -20° to give 1-(aziridine) carbonyl triethylammonium chloride (X) as a transient intermediate which proceeded to 2-chloroethyl isocyanate. At -10° this reaction produced N,N-diethyl-1-aziridinecarboxamide. Aziridine reacted with a large excess of phosgene in the absence of an acid acceptor to give N-2-(chloroethyl) carbamoyl chloride (III), 1,1′-bis(2-chloroethyl) urea (IV) and 2-(β-chloroethylamino)-2-oxazoline hydrochloride (V). Possible mechanisms for these reactions are discussed.     

Ringschlussreaktionen von 1-(2-Aminophenyl)-1-phenyl-äthylenen durch Kondensation mit Phosgen

Cyclization of 1-(2-aminophenyl)-1-phenyl-ethylenes or 1-(2-aminophenyl)-1-phenyl-propenes (II) by condensation with phosgene led to 4-phenyl-carbostyrils (III) or 2-chloro-4-phenyl-quinolines (IV). Similarly, thiophosgene afforded 4-phenyl-thiocarbostyril. Treatment of 1-(2-aminophenyl)-2-methyl-1-p-tolyl-propene (VII) with phosgene led to the corresponding isocyanate IX, which cyclized in the presence of aluminum chloride with loss of a methyl group to 3-methyl-4-p-tolyl-carbostyril (III-6). However, 1-(2-aminophenyl)-2-methyl-1-phenyl-propene (VIII) treated with phosgene gave the isocyanate XI and 3-phenyl-3-isopropenyloxindole (X). Cyclization of the isocyanate XI with aluminium chloride led simultaneously to 3-methyl-4-phenyl-carbostyril (XIV), and with migration of a methyl group to 3-methylene-4-methyl-4-phenyl-3. 4-dihydro-carbostyril (XV).     

Development of a monitoring tape for phosgene in air

A porous cellulose tape impregnated with a processing solution that includes 4-p-nitroben-zylpyridine, N-benzylaniline and methanol is a highly sensitive means of detecting phosgene and maintains stable sensitivity for at least three months in air in a desiccator. When the sample including phosgene was passed through the tape, the color of tape changed to red. The degree of color change was proportional to the concentration of phosgene at a constant sampling time and flow rate. The degree of color change could be recorded by measuring the intensity of reflecting light (555 nm). The detection limit was 6 ppb for phosgene with a sampling time of 60 sec and a flow rate of 400 ml/min. Reproducibility tests showed that the relative standard deviation of response (n = 10) was 2.6% for 0.2 ppm phosgene. No interference was observed from ethanol (1 vol.%), trichloroethylene (1 vol.%), acetone (1 vol.%), carbon dioxide (4.9 vol.%), carbon monoxide (100 ppm), nitrogen dioxide (100 ppm), sulfur dioxide (50 ppm), hydrogen chloride gas (5 ppm), chlorine (3 ppm), acetic acid gas (24 ppm), ammonia (40 ppm), or benzyl chloride (20 ppm).     

Reaction of phosgene with the tricycle related to the minor base of phenylalanine transfer ribonucleic acids

1-Benzylwye (8) underwent electrophilic substitution at the 7-position in the presence of phosgene and pyridine in tetrahydrofuran (THF) to afford the 1,4-dihydropyridines (11, 10, and 14) together with the carboxylic acid 6 and its methyl ester 2 after short treatment of the reaction mixture with methanol and then with water. When triethylamine was used instead of pyridine, phosgene reacted with triethylamine rather than 8, producing (E)-3-(diethylamino)propenoyl chloride (17) and diethylcarbamoyl chloride (18).     

Phosphazenium chloride catalysts immobilized on SBA-15 mesoporous material and silica gel: new exceptionally active catalysts for the chlorination of organic acids

Novel reusable phosphazenium chloride catalysts immobilized on SBA-15 mesoporous material and silica gel show exceptional activities and selectivities even in the continuous chlorination reaction of organic acids with thionyl chloride or phosgene.     

Photodecomposition of Chloroform Catalyzed by Unmodified MCM‐41 Mesoporous Silica

Unactivated MCM‐41 mesoporous silica catalyzes the photodecomposition of chloroform to phosgene and hydrogen chloride under near‐UV (λ > 360 nm) irradiation. The rate of photodecomposition increases toward an asymptotic limit as the O₂ partial pressure is increased. Deuterochloroform does not decompose under the same experimental conditions. Low concentrations of both cyclohexane and ethanol quench the photodecomposition, whereas water, up to its solubility limit, does not. Dissolved tetraalkylammonium salts suppress photodecomposition. The data are consistent with a mechanism in which light absorption by an SiO₂ defect yields an electron‐deficient oxygen atom, which then abstracts hydrogen from chloroform. The resulting CCl₃ radicals react with oxygen to form a peroxy radical that decomposes, eventually yielding phosgene and hydrogen chloride.     

Reaction of oxalyl and malonyl chloride with 1,1-dimethyl-2-substituted hydrazides

Recently we reported the reaction of 1,1-dimethyl-4-substituted semicarbazides with phosgene to occur with formation of several new heterocyclic ring systems. Here we report the reaction of several semicarbazides, thiosemicarbazides and related acyl substituted hydrazides with oxalyl chloride and malonyl chloride. These reactions occur with the formation of heterocyclic products which are oxadiazolinones, imidazolidinetriones, 2-thioxoimidazolindine-4,5-diones, and 2-thioxo-1,3-diazine-4,6-diones (2-thioxopyrimidine-4,6-diones).     

Bis-naphthalimide-based supramolecular self-assembly system for selective and colorimetric detection of oxalyl chloride and phosgene in solution and gas phase

Two bis-naphthalimide-based supramolecular gelators (NN-3 and NN-4) with a little difference of position of amino groups were designed and synthesized for the detection of oxaloyl chloride and phosgene. Energy transfer could be occurred between two naphthalimide groups in molecules NN-3 and NN-4. Yellow gels NN-3 and NN-4 were formed in some mixed solvents, and nanofibers with different size were obtained in these gels. The self-assembly processes of NN-3 and NN-4 in different solvents were investigated by UV-vis absorption, fluorescent spectra, SEM, FTIR, XRD and NMR. Gelators NN-3 and NN-4 could selectively detect oxaloyl chloride in solution and film states, but detect phosgene only in solution. NN-3 exhibited the ratiometric detection ability towards oxaloyl chloride and phosgene with the low limit of detection (LOD) of 210 nmol/L and 90 nmol/L, respectively. NN-4 as the corresponding control sample, it owned the higher LOD towards oxaloyl chloride and phosgene of 12.4 µmol/L and 64 µmol/L, respectively. Interestingly, films NN-3 and NN-4 could sensitively detect oxaloyl chloride gases with the low LOD of 2.0 ppm and 8.34 ppm, respectively. The detection mechanisms of NN-3 and NN-4 were well studied by ¹H NMR titration, HRMS and theoretical calculation.     

Thermal decomposition of poly(vinylidene chloride) prepared in presence of oxygen

The thermal decomposition of poly(vinylidene chloride) was studied for samples prepared in the presence of oxygen. The products from both mass and aqueous suspension polymerizations show two modes of thermal decomposition. A rapid initial mode varies in rate and extent with the amount of oxygen present. A slower mode is unaffected by oxygen and in similar in rate to the polymer made in the absence of oxygen. The chief volatile products are phosgene and formaldehyde for the rapid decomposition and hydrogen chloride for the slow decomposition. The rapid decomposition is interpreted to be an unzipping reaction of a vinylidene chloride–oxygen alternating copolymer initiated by homolysis of a peroxide bond. The absence of significant amounts of hydrogen chloride during this stage of decomposition shows that none of the free radicals generated are capable of initiating a chain reaction that would unzip hydrogen chloride from the poly(vinylidene chloride) backbone. The presence of oxygen during the aqueous suspension polymerization correlates with the generation of hydrochloric acid in the aqueous phase. By analogy with the high temperature decomposition, the hydrochloric acid is believed to result primarily from the hydrolysis of phosgene produced by partial decomposition of the polyperoxide. Initiation of the decomposition is believed due to a reaction of the chain propagating radical.     

Synthesis and Reactions of N-Chlorocarbonyl Isocyanate

Cl? CO? N?C?O (N-chlorocarbonyl isocyanate) is prepared in 90% yield by partial hydrolysis of the addition product of phosgene and cyanogen chloride. Many derivatives of the iminocarboxylic acid parent compound can be obtained from this highly reactive species. Both the acid chloride and the isocyanate group are amenable to reactions exhibiting overall selctivity, and this opens the way, inter alia, to a simple preparative synthesis of isocyanates from alcohols, phenols, thiols, and thiophenols. Combination of the two functional groups and their peculiar symmetry, which becomes evident, e.g. in the HCl adduct, facilitates ready cyclization of N-chlorocarbonyl isocyanate under very mild conditons.     

Debenzylation of tertiary amines using phosgene or triphosgene: an efficient and rapid procedure for the preparation of carbamoyl chlorides and unsymmetrical ureas. Application in carbon-11 chemistry

Efficient and rapid preparations of carbamoyl chlorides and unsymmetrical ureas from tertiary amines and phosgene or its safe equivalent triphosgene [bis(trichloromethyl)carbonate, BTC] are described. First, the reaction of stoichiometric amounts of phosgene with secondary amines was revisited, and it was shown that the formation of carbamoyl chlorides in high yields required careful adjustments of experimental conditions and the use of pyridine as an HCl scavenger. A phosgene-mediated dealkylation of triethylamine was observed when this base was used instead of pyridine. Taking advantage of this observation, a strategy of synthesis of carbamoyl chlorides from tertiary amines and phosgene has been developed. N-Alkyl-N-benzyl(substituted)tetrahydroisoquinolines, -piperazines, -piperidines, or -anilines were treated with stoichiometric amounts of phosgene (or BTC) in CH(2)Cl(2). Tertiary amines bearing electron-enriched benzyl group(s) afforded carbamoyl chlorides in excellent yields and without any contamination by symmetrical ureas. Subsequent additions of primary or secondary amines to these carbamoyl chlorides produced unsymmetrical ureas in single-pot and high-yielding operations. This methodology was applied in (11)C-chemistry. From [(11)C]phosgene, a common precursor used in the preparation of radiotracers for positron emission tomography, a rapid and efficient synthesis of (11)C-carbamoyl chlorides and (11)C-unsymmetrical ureas derived from tetrahydroisoquinoline and piperazine is described. The first example of (11)C-amide formation from the reaction of a (11)C-carbamoyl chloride and an organometallic (cyanocuprate or a Grignard reagent in the presence of a nickel catalyst) is also presented.