Carbamates derivatives

The Finnish viscose producer Kemira Oy Saeteri collaborated with Neste Oy on the development of a carbamate derivative route. This system is based on work (89) that showed that the reaction between cellulose and urea gives a derivative easily dissolved in dilute sodium hydroxide ... 

Up until 1986 the major use for 2-j -butylphenol was in the production of the herbicide, 2-j -butyl-4,6-dinitrophenol [88-85-7] which was used as a pre- and postemergent herbicide and as a defoHant for potatoes (30). The EPA banned its use in October 1986 based on a European study which showed that workers who came in contact with 2-j -butyl-4,6-dinitrophenol experienced an abnormally high rate of reproduction problems. Erance and the Netherlands followed with a ban in 1991. A significant volume of 2-j -butyl-4,6-dinitrophenol is used worldwide as a polymerization inhibitor in the production of styrene where it is added to the reboiler of the styrene distillation tower to prevent the formation of polystyrene (31). OSBP is used in the Par East as the carbamate derivative, 2-j -butylphenyl-Ai-methylcarbamate [3766-81-2] (BPMC) (32). BPMC is an insecticide used against leaf hoppers which affect the rice fields. 

Another significant use of 3-methylphenol is in the production of herbicides and insecticides. 2-/ f2 -Butyl-5-methylphenol is converted to the dinitro acetate derivative, 2-/ f2 -butyl-5-methyl-4,6-dinitrophenyl acetate [2487-01 -6] which is used as both a pre- and postemergent herbicide to control broad leaf weeds (42). Carbamate derivatives of 3-methylphenol based compounds are used as insecticides. The condensation of 3-methylphenol with formaldehyde yields a curable phenoHc resin. Since 3-methylphenol is trifunctional with respect to its reaction with formaldehyde, it is possible to form a thermosetting resin by the reaction of a prepolymer with paraformaldehyde or other suitable formaldehyde sources. 3-Methylphenol is also used in the production of fragrances and flavors. It is reduced with hydrogen under nickel catalysis and the corresponding esters are used as synthetic musk (see Table 3). 

Carbamates derived from chloroformates are used to manufacture pharmaceuticals, including tranquili2ers (58), antihypotensives, and local anesthetics, pesticides, and insecticides (see Carbamic acid). 

Phenethyl carbamate derivatives 30 have also been employed in Bischler-Napieralski reactions cyclization of these substrates affords 3,4-dihydroisoquinolones 31. These reactions have been conducted using a variety of different promoters including PPA, POCl3, and Tf20. Mixtures of P2O5 and POCI3 appear to afford the best results in some cases. 

The carbamates, derived from the reaction of 8-aminoquinoline with phenyl or ethyl chloroformate, upon reduction with NaBH4 gave the... 

Allylsilanes are available by treatment of allyl acetates and allyl carbonates with silyl cuprates17-18, with antarafacial stereochemistry being observed for displacement of tertiary allyl acetates19. This reaction provides a useful asymmetric synthesis of allylsilanes using esters and carbamates derived from optically active secondary alcohols antarafacial stereochemistry is observed for the esters, and suprafacial stereochemistry for the carbamates20,21. 

Z)-3-Alkoxyallylstannanes of high optical purity are available by stannylation of lithiated allyl carbamates derived from optically active allyl alcohols118. 

Lin, A. J. Shansky, C. W. Sartorelli, A. C. Potential bioreductive alkylating agents. 3. Synthesis and antineoplastic activity of acetoxymethyl and corresponding ethyl carbamate derivatives of benzoquinones. J. Med. Chem. 1974, 17, 558-561. 

Okawara et al. reported the photodissociation of several carbamate derivatives on the basis of the product analysis [166]. They demonstrated that the cleavage bonds were different corresponding to the number of the methylene groups in Eq. (43). When n was unity, the reactive benzyl radical and less-reactive thiyl radical were produced. 

Cambon, C., C. Declume, and R. Derache. 1979. Effect of the insecticidal carbamate derivatives (Carbofuran, Pirimicarb and Aldicarb) on the activity of acetylcholinesterase in tissues from pregnant rats and fetuses. Toxicol. Appl. Pharmacol. 49 203-208. 

The mechanism of the stereoselective syntheses of (K)-3-aryl-5-(hydroxy-methyl)oxazolidinones via the Mannenin reaction of aryl carbamic acid esters with (Jt)-glycidyl butyrate has been explored in detail by Brickner et al. [60]. Namely, N-lithiated carbamate derivatives of anilines are allowed to react with the commercially available (K)-glycidyl butyrate (96-98% enantiomeric excess ee) under appropriate conditions to obtain enantiomerically pure (Jt)-3-aryl-5-(hydroxymethyl)oxazolidinones in 85-99% yields, according the pathways depicted in Scheme 19. 

Compounds which are of interest in this context include 4-oxadiazolylpyrid-azines (35, R = cyclopropyl, Et) [117], 6-aryloxy-2-hydroxyalkyI-3(27/)-pyri-dazinones [118], 3-halo-6-hydrazinopyridazines of type (36, R = substituted amino) [119], Ar-2-isoxazolylmethyl-substituted 3-iminopyridazines (37) [ 120], carbamates derived from 3,6-bis(hydroxymethyl)-4-pyridazinones (38, R = alkyl, Ph) [121], and iminodihydropyridazine derivatives (39, R1 = acyl R2 = H,MeS R3 = aryl) [122, 123]. In Hungary, antidepressant activity has been observed with some 3,6-disubstituted pyridazines of type (40) [124]. 

Conversion to carbamates. Cyclic carbamates derived from sugars and related compounds have repeatedly been encountered, the first being an inosamine derivative, obtained by Curtius degradation of dihydroshikimic acid.82,83... 

Friesen et al. reported that 2,3-allenols 340 can be converted to the corresponding carbamate derivatives 343, in which the terminal C=C bond of the allene moiety can be iodinated to afford diiodides 344. Under the catalysis by an Ag+ salt, compounds 344 react to give iminocarbonates 345 and oxazolindinones 346, leading to diols 347 and amino alcohols 348, respectively, after hydrolysis (Scheme 10.138) [160-162], A similar reaction was observed with trichloroacetimidates 350 [163],... 

Potential Uses of These Polymers. We have studied the phenyl isocyanate modification of poly(vinyl alcohol) as a model system. Many uses exist for carbamates as medicines, pesticides and herbicides (67,68). For example, ethyl carbamate has been used to treat leukemia and multiple myeloma. Ethyl carbamate has also been used as an antidote for central nervous system poisoning by strychnine. The tranquilizer Meprobamate is a carbamate derivitive. Numerous pesticides and herbicides, such as Sevin and Propham, are also carbamate derivatives. Propham is isopropyl N-phenylcarbamate which bears a strong resemblence to the polymers of Equation 21, and this compound is used as a preemergence herbicide. Numerous other close analogs could be cited also. We might note also that the N-phenyl carbamoyl unit bears... 

Carbamate derivatives (Table 1) of cellulose, chitin, amylose, amylopectin, and dextran were prepared using the isocyanates described in Part A of the Experimental Section. Amylose, amylopectin, dextran, and cellulose were obtained from Polysciences, Inc. and used without further purification. Chitin, obtained from Eastman Kodak, was decalcified and deproteinated by the method reported by Haye r prior to use. 

Preweighed 1.0 mg samples of each polysaccharide carbamate derivative were submerged in aqueous solutions at three pH values 3.1 7.0 and 11.3. Three milliliter aliquots were withdrawn at periodic intervals and analyzed by ultraviolet spectroscopy. Typical results are shown in Figures 3 and 4 for pendant hydrolysis rates of carbamate derivatives of cellulose and chitin respectively as a function of pH. 

Figures 3 and 4 illustrate typical rates of hydrolysis for carbamate derivatives of cellulose and chitin. The rates of release at a pH value 11.3 were considerably higher in both systems than at pH values of 3.1 and 7.0. After seven days in the basic medium the cellulose derivative had delivered 27.3 percent of the available aniline. In the acidic medium and neutral medium 15.6 and 10.6 percent were delivered. After seven days the chitin derivative delivered 27.7, 10.0, and 9.5 percent of the available p-methylaniline in the basic, acidic, and neutral media, respectively.

Scheme 12 Synthesis of cis and trans 1-hydroxymethyl substituted C6-HSL and their carbamate derivatives... 

Another recently reported case is that of the antiarrhythmic agent moric-izine, an ethyl carbamate derivative of a primary aromatic amine (R-NH-C0-0-CH2CH3) [109]. Hydrolysis to the carbamic acid... 

Fig. 8.19. Sequential activation of acetoxymethyl carbamate derivatives of secondary amines, as exemplified with a model amine. The sequence is initiated by chemical and enzymatic hydrolysis of the terminal ester group [209][210]. 

Ferrero, M., Fernandez, S. and Gotor, V., Selective alkoxycarbonylation of A-ring precursors of vitamin D using enzymes in organic solvents. Chemoenzymatic synthesis of lo ,25-dihydroxyvi-tamin D3 C-5 A-ring carbamate derivatives. J. Org. Chem., 1997, 62, 4358. 

It is also worthwhile to outline at this place the immobilization procedure that was used for the preparation of type I CSPs A bifunctional linker with a terminal isocyanate on one side and a triethoxysilyl group on the other end (3-isocyanatopropyl triethoxysilane) was reacted with the native cinchona alkaloids quinine and quinidine and subsequently the resultant carbamate derivative in a second step with silica [30], Remaining silanols have been capped with silane reagents, yet, are less detrimental for acidic solutes because of the repulsive nature of such electrostatic interactions. CSPs prepared in such a way lack the hydrophobic basic layer of the thiol-silica-based CSPs mentioned earlier, which may be advantageous for the separation of certain analytes. 

Various papers have been published that investigated the thermodynamics of host-guest associations of cinchonan carbamate derivatives either in solution with the chiral selectors (i.e., the soluble precursors of CSPs) on the one hand [87,88] or... 

Scheme 6.3S. Interpretation of the chirality transfer during the course of allylic substitution of acyclic carbamate derivative (R)-163.

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