Ureas tetramethylurea

Amides such as DMF or ureas such as N,N-tetramethylurea react with bis(trimethylsilyl)selenide 604 in the presence of BF3-OEt2 to give selenoamides, for example 617, or selenoureas whereas esters such as n-butyl benzoate react with 604 in the presence of Bp3-Et20 and 2,3-dimethylbutadiene to give 619 via 618 [157]. On heating with P4Sio/sulfur and hexamethyldisiloxane 7 y9-ketoesters such as ethyl acetoacetate are converted to 3H-l,2-dithiole-3-thiones such as 620 in high yields [158] (Scheme 5.51 cf. also Section 8.6). 

Urea (27 g), tetramethylurea (TMU, 0.8 g), copper powder (2.13 g), 19.95 g phthalic anhydride, 0.105 g molybdic anhydride, and trichlorobenzene (mixture of isomers, 72 g) were introduced in the above order into the reactor. The reaction mixture was heated from 20 to 170°C in 90 min with stirring and then kept at 170°C for 5 hr. The volatile portion was distilled off (at... 

Therefore, the solvent used for successful electrosynthesis of PcCu should be inert in relation to PA and, on the other hand, should have electroconductivity. The compounds used as promoters [41] could theoretically serve as such solvents. Tetramethylurea (TMU) and l-methyl-2-pyrolidinone were chosen by the authors of Ref. 32 among other promoters used in the work [41]. The first one has a nature close to that of the principal precursor (urea), and thus should not influence the reaction course negatively. The TMU has sufficient conductivity to permit electrolysis in its medium, and reasonable viscosity. The boiling point of 174-178 C is ideal for such research, since conventional syntheses of Pc from urea and PA are carried out at similar temperatures. The results of TMU use as a solvent are presented in Table 5.7. The results seem promising, and this solvent is recommended to study Pc formation in its medium in further research work. In the case of l-methyl-2-pyro-lidinone, no phthalocyanine formation was observed. No phthalocyanine was observed also in the following systems (1) urea, PA, TBA, TMU (without copper) (2) urea, PA, TBA, TMU, Sb, or Mg (anodes (3) TMU, urea (or without urea), phthalimide, TBA (in all cases with or without electrolysis). 

As mentioned earlier (Example 16, Table 5.6), an abundance of urea does not affect the reaction course of 1,3-D cyclization. Tetramethylurea can participate in similar intermediate reactions as urea due to the proximity of their nature. Theoretically, it is possible to obtain metal-free phthalocyanine by adding other catalysts and/or promoters the reaction mixture on the basis of TMU or other derivatives of urea. 

In contrast, dipolar aprotic solvents possess large relative permittivities (sr > 15), sizeable dipole moments p > 8.3 10 ° Cm = 2.5 D), and average C.f values of 0.3 to 0.5. These solvents do not act as hydrogen-bond donors since their C—H bonds are not sufficiently polarized. However, they are usually good EPD solvents and hence cation sol-vators due to the presence of lone electron pairs. Among the most important dipolar aprotic solvents are acetone, acetonitrile [75], benzonitrile, A,A-dimethylacetamide [76, 77], A,A-dimethylformamide [76-78], dimethylsulfone [79], dimethyl sulfoxide [80-84], hex-amethylphosphoric triamide [85], 1-methylpyrrolidin-2-one [86], nitrobenzene, nitro-methane [87], cyclic carbonates such as propylene carbonate (4-methyl-l,3-dioxol-2-one) [88], sulfolane (tetrahydrothiophene-1,1-dioxide) [89, 90, 90a], 1,1,3,3-tetramethylurea [91, 91a] and tetrasubstituted cyclic ureas such as 3,4,5,6-tetrahydro-l,3-dimethyl-pyr-imidin-2-(l//)-one (dimethyl propylene urea, DMPU) [133]. The latter is a suitable substitute for the carcinogenic hexamethylphosphoric triamide cf. Table A-14) [134]. 

N-bridging cyanate in low yields (17-23% after heating for 24 h Scheme 11). Conversion was found to proceed at comparable rates in ethanol or acetonitrile, and it was thus concluded that hydrolytic processes by traces of water do not play a role. Cyanate formation also was observed with Af-methylurea or 7/,7/-dimethylurea, but not with Af,A -dimethylurea or tetramethylurea, which shows that at least one NH2 group is essential for the elimination reaction to occur. A possible interpretation is that bridging of urea over the binuclear core through its O atom and one amino N atom is a key step for the conversion (58). This finding is in line with the discovery of urea-to-cyanate transformation for several pyrazolate-based dinickel complexes with urea bound in the N,0-bridging mode (see below). 

Urea, 1,1,3,3-tetramethyl-. See Tetramethylurea Urea, (3-(triethoxysilyl) propyl)-. Seey-Ureidopropyltriethoxysilane N-(Triethoxysilylpropylj urea Urea, 1,1,3-trimethyl-2-thio. See Trimethylthiourea 5-Ureidohydantoin. See Allantoin 5-Ureidonorvaline. See Citrulline Ureidopropyltriethoxysilane. Seey-Ureidopropyltriethoxysilane N-(Triethoxysilylpropylj urea 3-Ureidopropyltriethoxysilane. See y-Ureidopropyltriethoxysilane N-(Triethoxysilylpropylj urea y-Ureidopropyltriethoxysilane CAS 23779-32-0 EINECS/ELINCS 245-876-7 Synonyms N,N -Bis [3-(triethoxysilyl) propyl] urea (3-(Triethoxysilyl) propyl) urea N-(Triethoxysilylpropyl) urea Urea, (3-(triethoxysilyl) propyl)- Ureidopropyltriethoxysilane 3-Ureidopropyltriethoxysilane Empirical CioH24N204Si Properties M.w. 264.40 dens. 0.92 m.p. -97 C flash pt. 14 C ref. index 1.386 (20 C)... 

DMA A,A-dimethylacetainide AN acetonitrile DMTF A,A-dimethylthioformamide DMPU 1,3-dimethylpropylene urea Py pyridine TMU tetramethylurea PDA 1,3-propanediamine three M—O bonds one M—S bond Jahn-Teller distorted octahedron four equatorial Cu—O bonds second-order Jahn-Teller distorted octahedron Hg—Hg bond length 250 pm two bonds are longer... 

As far as neutral nitrogen ligands are concerned, a patent elaimed the use of amides or ureas (e.g. tetramethylurea, but oxygen-containing sulphur compounds were also mentioned) as promoters for the Ru3(CO)i2-eatalysed (rhodium compoimds were also mentioned) synthesis of ureas from nitroarenes and anilines... 

An ice-cold soln. of urea in methanol added all at once to 3-chloro-3-phenylphthalide and after 1 min. the solvent rapidly removed on a rotatory evaporator under reduced pressure methyl i/ -0-benzoyIhenzoate. Y ca. 90%. - Urea (or alkylated ureas such as tetramethylurea) may be used as a base in place of the more expensive and malodorous pyridine. F, e. s. M. S. Newman and L. K. Lala, Tetrah. Let. 1967, 3267. 

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