N-Phenylcarbamates

Reaction of methyl a-L-rhamnopyranoside with triphenylboroxole gave a syrupy boronate ester which was characterized as a crystalline phenyl-carbamate. Removal of the phenylboronic acid residue gave a product identified as methyl a-L-rhamnopyranoside 4-N-phenylcarbamate, since it was identical with that resulting from removal of the ketal group from methyl 2,3-O-isopr opylidene-a-L-rhamnopyranoside 4-N-phenylcarbamate (12). This establishes the structure of the original ester as methyl a-L-rhamnopyranoside 2,3-phenylboronate (24). 

The N-phenylcarbamic acid methyl ester was purchased from TCI America. 

Phenylcarbamate herbicides, 13 320 N-Phenylcarbamate herbicides, 13 303 Phenyl chloroformate... 

In 20% dioxan (Hegarty et ai, 1974). The reference reaction is nucleophilic attack by alkoxide ions on phenyl N-methyl-N-phenylcarbamate at 25° in water (Hutchins and Fife, 1973). The rate constant for bimolecular attack by an oxyanion of pKt 4.26 (3.6 x 10-13 dm3 mol-1 s-1) is obtained by a long extrapolation of a two point Bronsted plot (which has the reasonable slope of 0.90)... 

Hutchins and Fife, 1973. The reference reaction is the attack of the anion of a phenol of pX, 9.0 on phenyl N-methyl-N-phenylcarbamate under the same conditions f 18 times slower than B.3.1... 

Fife et ai, 1975. The reference reaction is attack by 2-aminoethanethiolate anion (pA, 8.3) onp-nitrophenyl N-methyl-N-phenylcarbamate, corrected to pK 8.7... 

Fife et al., 1975. The EM is based on an estimated lower limit for the rate of the reaction of cyclohexylamine with p-nitrophenyl N-methyl-N-phenylcarbamate (aniline does not react at all) and requires a long extrapolation from pK, 10.7 to 2.7, using 0 = 0.8... 

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... 

MethyUndanes, 20 281 Methylindene, cyclization, 28 298 Methylnaphthalene, cyclization, 28 298, 299 Methyl-N-phenylcarbamate synthesis, 41 226-227... 

A-Ethoxycarbony 1-1H-azepine is converted rapidly (5 min) and quantitatively into ethyl N -phenylcarbamate by boron trifluoride (81JCS(P1)447). The dichloroborane (15 R1 = H, R2 = BCl2) results from the action of boron trichloride on 10,11-dihydro-5//-dibenz[f>,/]azepine (74IC2783). 

Williams, A., Participation of an elimination mechanism in alkaline hydrolysis of alkyl N-phenylcarbamates , J. Chem. Soc. Perkins, II, 1244-1247 (1973). 

Izumi et al. (369) found that Keggin-type heteropolyanions containing Mo or V show a promoting effect in the reductive carbonylation of nitrobenzene by PdCl2 to form methyl N-phenylcarbamate in the presence of methanol (Eq. 44) ... 

The thermolysis of the corresponding N -phenylcarbamate takes place at a lower temperature (310 °C) (Scheme 2)12,14. 

The use of DNS-C1 for the fluorimetric analysis of N-phenylcarbamate and urea herbicides has been examined [175]. The herbicides are hydrolyzed in 2Npotassium hydroxide in... 

Herbicides that act as inhibitory uncouplers are dinitro-phenols, N-phenylcarbamates, acylanilides, halogenated benzoni-triles, substituted imidazoles, substituted benzimidazoles, bromofenoxim, substituted 2,6-dinitroanilines, pyridinols, and substituted 1,2,4-thiadiazoles (2). 

Figure 3. Correlation of pl50 and partition data for some substituted phenyldimethyl-ureas and isopropyl N-phenylcarbamates [adapted from Hansch and Deutsch (12)]...

The preparation of N-phenylcarbamates from incompletely substituted, carbohydrate boronates is, perhaps, the least destructive of esterifying reactions, requiring only that the compounds be heated with phenyl isocyanate in dry benzene or toluene. Several reports have appeared on successful application to glycoside,22,51,58,69 sugar,47 and alditol23 derivatives. 

---