t-Carbinamines, RR'R″CNH<sub>2</sub>. III. The Preparation of Isocyanates, Isothiocyanates and Related Compounds<sup>1</sup>

Bortnick, Newman M.; Luskin, Leo S.; Hurwitz, Melvin D.; Rytina, A. W.

doi:10.1021/ja01598a043

Cited by 35 publications

(4 citation statements)

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“…1H NMR (CDCl3): 8 4.33 (4H, cm, NCH2CH2CH2CH3), 3.71 (2H, s, ring CH2), 1.63 (4H, cm, NCH2CH2CH2CH3), 1.35 (4H, cm, NCH2CH2CH2CH3), 0.94 (6H, t, J = 6.2 Hz, methyl). Other oxonols were made using the same procedure, starting with the appropriate thiourea (prepared from requisite primary amine and carbon disulfide) (Bortnick et al 1956). All of the oxonols described have similar NMR spectra.…”

Section: Materials and Methods Chemistrymentioning

confidence: 99%

Voltage sensing by fluorescence resonance energy transfer in single cells

González

Tsien

1995

Biophysical Journal

165

122

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A new mechanism has been developed for achieving fast ratiometric voltage-sensitive fluorescence changes in single cells using fluorescence resonance energy transfer. The mechanism is based on hydrophobic fluorescent anions that rapidly redistribute from one face of the plasma membrane to the other according to the Nernst equation. A voltage-sensitive fluorescent readout is created by labeling the extracellular surface of the cell with a second fluorophore, here a fluorescently labeled lectin, that can undergo energy transfer with the membrane-bound sensor. Fluorescence resonance energy transfer between the two fluorophores is disrupted when the membrane potential is depolarized, because the anion is pulled to the intracellular surface of the plasma membrane far from the lectin. Bis-(1,3-dialkyl-2-thiobarbiturate)-trimethineoxonols, where alkyl is n-hexyl and n-decyl (DiSBA-C6-(3) and DiSBA-C10-(3), respectively) can function as donors to Texas Red labeled wheat germ agglutinin (TR-WGA) and acceptors from fluorescein-labeled lectin (FI-WGA). In voltage-clamped fibroblasts, the translocation of these oxonols is measured as a displacement current with a time constant of approximately 2 ms for 100 mV depolarization at 20 degrees C, which equals the speed of the fluorescence changes. Fluorescence ratio changes of between 4% and 34% were observed for a 100-mV depolarization in fibroblasts, astrocytoma cells, beating cardiac myocytes, and B104 neuroblastoma cells. The large fluorescence changes allow high-speed confocal imaging.

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Section: Materials and Methods Chemistrymentioning

confidence: 99%

Voltage sensing by fluorescence resonance energy transfer in single cells

González

Tsien

1995

Biophysical Journal

165

122

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“…4.3 Amines. The carbamation of primary amines with DMC is a known process, though only catalyzed reactions proceed with good yields and selectivity (Scheme ) 16 Carbamation of Amines with DMC Cat.…”

Section: Dmc As a Methoxycarbonylating Agentmentioning

confidence: 99%

The Chemistry of Dimethyl Carbonate

2002

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Dimethyl carbonate (DMC) is a versatile compound that represents an attractive eco-friendly alternative to both methyl halides (or dimethyl sulfate) and phosgene for methylation and carbonylation processes, respectively. In fact, the reactivity of DMC is tunable: at T = 90 degrees C, methoxycarbonylations take place, whereas at higher reaction temperatures, methylation reactions are observed with a variety of nucleophiles. In the particular case of substrates susceptible to multiple alkylations (e.g., CH(2)-active compounds and primary amines), DMC allows unprecedented selectivity toward mono-C- and mono-N-methylation reactions. Nowadays produced by a clean process, DMC possesses properties of nontoxicity and biodegradability which makes it a true green reagent to use in syntheses that prevent pollution at the source. Moreover, DMC-mediated methylations are catalytic reactions that use safe solids (alkaline carbonates or zeolites), thereby avoiding the formation of undesirable inorganic salts as byproducts. The reactivity of other carbonates is reported as well: higher homologues of DMC (i.e., diethyl and dibenzyl carbonate), are excellent mono-C- and mono-N-alkylating agents, whereas asymmetrical methyl alkyl carbonates (ROCO(2)Me with R > or = C(3)) undergo methylation processes with a chemoselectivity up to 99%.

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“…Finally, the present procedure was compared to a conventional method for the synthesis of methyl urethanes with ClCO 2 Me as the methoxycarbonylating agent . Amines 2d , e and 2h , i were chosen as substrates.…”

Section: Resultsmentioning

confidence: 99%

“…Scheme . A procedure of methoxycarbonylation of amines with ClCO 2 Me was used . In a 10-mL flask, the amine (0.5 g) was dissolved in toluene (3 mL) and an aqueous solution of K 2 CO 3 (1.7 M, 3 mL) was added.…”

Section: Methodsmentioning

confidence: 99%

Synthesis of Methyl Carbamates from Primary Aliphatic Amines and Dimethyl Carbonate in Supercritical CO₂: Effects of Pressure and Cosolvents and Chemoselectivity

et al. 2005

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At 130°C, in the presence of CO 2 (5-200 bar), primary aliphatic amines react with dimethyl carbonate (MeOCO 2 Me, DMC) to yield methyl carbamates (RNHCO 2 Me) and N-methylation sideproducts (RNHMe and RNMe 2 ). The pressure of CO 2 largely influences both the reaction conversion and the selectivity toward urethanes: in general, conversion goes through a maximum (70-80%) in the midrange (40 bar) and drops at lower and higher pressures, whereas selectivity is continuously improved (from 50% up to 90%) by an increase of the pressure. This is explained by the multiple role of CO 2 in (i) the acid/base equilibrium with aliphatic amines, (ii) the reactivity/solubility of RNHCO 2 -nucleophiles with/in DMC, and (iii) the inhibition of competitive N-methylation reaction of the substrates. Cosolvents also affect the reaction: in particular, a drop in selectivity is observed with polar protic media (i.e., MeOH), plausibly because of solvation effects (through H-bonds) of RNHCO 2-moieties. The reaction shows also a good chemoselectivity: bifunctional aliphatic amines bearing either aromatic NH 2 or OH substituents [XC 6 H 4 (CH 2 ) n NH 2 , X ) NH 2 , OH; n ) 1, 2], undergo methoxycarbonylation reactions exclusively at aliphatic amino groups and give the corresponding methyl carbamates [XC 6 H 4 (CH 2 ) n NHCO 2 Me] in 39-65% isolated yields.

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t-Carbinamines, RR'R″CNH₂. III. The Preparation of Isocyanates, Isothiocyanates and Related Compounds¹

Cited by 35 publications

References 0 publications

Voltage sensing by fluorescence resonance energy transfer in single cells

Voltage sensing by fluorescence resonance energy transfer in single cells

The Chemistry of Dimethyl Carbonate

Synthesis of Methyl Carbamates from Primary Aliphatic Amines and Dimethyl Carbonate in Supercritical CO₂: Effects of Pressure and Cosolvents and Chemoselectivity

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t-Carbinamines, RR'R″CNH2. III. The Preparation of Isocyanates, Isothiocyanates and Related Compounds1

Cited by 35 publications

References 0 publications

Voltage sensing by fluorescence resonance energy transfer in single cells

Voltage sensing by fluorescence resonance energy transfer in single cells

The Chemistry of Dimethyl Carbonate

Synthesis of Methyl Carbamates from Primary Aliphatic Amines and Dimethyl Carbonate in Supercritical CO2: Effects of Pressure and Cosolvents and Chemoselectivity

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Product

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t-Carbinamines, RR'R″CNH₂. III. The Preparation of Isocyanates, Isothiocyanates and Related Compounds¹

Synthesis of Methyl Carbamates from Primary Aliphatic Amines and Dimethyl Carbonate in Supercritical CO₂: Effects of Pressure and Cosolvents and Chemoselectivity