Hydrogenation carbamates

Trialkanolamines, lacking an amine hydrogen, do not undergo die carbamate reaction. 

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). 

Hg(OAc)2, H2O, 80% AcOH, HSCH2CH2SH, 25°, 5-20 min H2S, 2 h, high yield. The removal of an 5-benzylthiomethyl protective group from a dithioacetal with mercuiy(II) acetate avoids certain side reactions that occur when an 5-benzyl thioether is cleaved with sodium/ammonia. The dithioacetal is stable to hydrogen bromide/acetic acid used to cleave benzyl carbamates. 

Benzyl carbamates of pyrrole-type nitrogens can be cleaVfed with nucleophilic reagents such as hydrazine hydrogenation and HF treatment are also effective. ... 

Fluorodediazoniation of alkyl carbamates in hydrogen fluonde/pyndine (70/30) represents a novel route to alkyl fluoroformates [6, 9] (equation 4)... 

The cyanomethyl ether, formed from bromoacetonitrile (acetone, K2CO3, 97-100% yield), is cleaved by hydrogenation of the nitrile with Pt02 in EtOH, in 98% yield. The method has also been used for the protection of amines and carbamates. 

Decarbamoylation and acylation of 204 which was prepared by catalytic hydrogenation of the corresponding carbamate (71BCJ520) afiforded 22. A diazotransfer reaction upon treatment of 22 (R = C02Me or COMe) with... 

The salts of alkyl xanthates, A/,A/ -di-substituted dithio-carbamates and dialkyidithiophosphates [26] are effective peroxide decomposers. Since no active hydrogen is present in these compounds, an electron-transfer mechanism was suggested. The peroxide radical is capable of abstracting an electron from the electron-rich sulfur atom and is converted into a peroxy anion as illustrated below for zinc dialkyl dithiocarbamate [27] ... 

To complete the synthesis of thienamycin, it only remains to cleave the carbamate and ester functions in 23. Catalytic hydrogenation of 23 accomplishes both of these objectives, and furnishes (+)-thienamycin (1). Synthetic (+)-thienamycin, prepared in this manner, was identical in all respects with natural thienamycin. 

If R2 contains an a-hydrogen the method cannot be applied as enaminc formation occurs. Bisamides (or -carbamates) are often used in amidoalkylations of aryl and reactive methylene compounds, but the rather harsh reaction conditions severely limit application in the synthesis of more complicated molecules with other functional groups. 

The isocyanate group is reactive, a feature which leads to a large number of possible reactions when crosslinking is carried out. The essential feature of all the processes is that they involve reaction, initially at least, with an active hydrogen atom in the molecules of the co-reactant. For example, isocyanates will react with water, as illustrated in Reaction 4.10, to generate an unstable intermediate, a carbamic acid, which releases carbon dioxide to yield an amine. 

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