Chloroformates with tert amines

As a result of these findings, the combined use of the two azophenol hosts, Po04 (64, n = 1) and pyridine dye 66, is able to discriminate the substitution pattern of amines, i.e. prim., sec. and tert. amines. In other words, when an unknown alkylamine is treated with Po04 in chloroform and the yellow solution remains unchanged, the amine should be a tert. amine (Fig. 20). On addition of pyridine dye 66 in chloroform to the unknown amine which shows color change with Po04,... 

The reaction of methyl chloroformate with amines to give methyl carbamates is exothermic and, due to large heat release, hot spots occur [45]. This is even observed at the laboratory scale when using N-methoxycarbonyl-L-tert-leucine. 

Yields higher than about 70% for any of these isonitrile preparations generally indicate incomplete fractionation. The purity of the product may be conveniently checked by proton magnetic resonance spectroscopy. The characteristic 1 1 1 triplet for tert-butyl isocyanide appears at <5 1.45 (chloroform-d). A small upheld peak usually indicates the presence of unreacted amine. Other common contaminants are dichloromethane and chloroform The purity may be determined more accurately by gas chromatographic analysis on a 230 cm. by 0.6 cm. column packed with 10%SE30 on Chromosorb G, 60-80 mesh, at 80°. 

The oxidation of some aliphatic amines is a good route to aliphatic nitro compounds. tert-Butylamine is oxidized in 83% yield to 2-methyl-2-nitropropane by potassium permanganate in water at 45 °C for 8 h and at 55 °C for 8 h [738, 892], Under similar conditions, 4-amino-2,2,4-tri-methylpentane is converted into 4-nitro-2,2,4-trimethylpentane in 69-82% yields [859]. Refluxing 3a-acetoxy-20a-amino-5p-pregnane with a chloroform solution of m-chloroperoxybenzoic acid for 40 min furnishes 3a-acetoxy-20a-nitro-5p-pregnane in 66% yield [379]. 2-Aminobutane is converted into 2-nitrobutane by peroxyacetic acid [253] or dimeth yldioxirane [277] (equation 498). 

In a typical run, 5 mmoles of fert-butylamine in chloroform reacted with 4.1 mmoles of ozone in an ozone-nitrogen stream at about —60°C. to give 0.9 mmole (18%) of 2-methyl-2-nitropropane (XI), 0.9 mmole (18% ) of tert-h iiy isocyanate (XVI), and 3.0 mmoles (60% ) of tert-butylammonium chloride (XIV). In a separate but similar run, 3.5 mmoles of molecular oxygen were determined as a product. Under the conditions of the reaction no significant reaction occurred between ferf-butylamine and chloroform in the absence of ozone or between ozone and chloroform in the absence of the amine. 

Removal of the methoxymethyl groups from 43 with HCl, followed by protection of the secondary amine with benzyl chloroformate afforded the carbamate 9. Selective silylation of the 4-hydroxy group of 9 by treatment with 1.2 equiv of tert-butyldimethylsilyl chloride and 2.4 equiv of imidazole in DMF at room temperature for 1 h afforded the corresponding silyl ether as a single isomer in 80% yield that was subjected to acetylation at the C-3 hydroxyl group to afford the carbamate 11, which upon removal of the Cbz and TBDMS groups furnished 1. 

A year later, MCM-41 was used to prepare a Cr(salpr)MCM-41 (salpr=Ar,Ai -bis(3-salicylidenaminopropyl)amine) catalyst for the benzylic oxidation of allqrl aromatics. Masteri-Farahani et al. used a chloropropyl-modified MCM-41 material that was mixed with a [Cr(salpr)(H20)Cl] complex to produce their chromium catalyst. Using tert-bulylhydroperoxide (TBHP) as an oxidant, a mixture of the catalyst and substrate in solvent (chloroform or the substrate itself) was reacted for 7 h to afford the oxidised product. The substrates tested were toluene and ethyl benzene, which showed high selectivity towards the oxidised product benzaldehyde or acetophenone, respectively. 

In the polycondensation step, a monofunctional phenol (such as 3-5 mol% phenol, p-tert-butylphenol, p-cumylphenol) is added as a chain terminator to control the molecular weight of the final polycarbonate. Reaction partners are now end groups (chloroformate and phenolic -OH see above) and reaction rates decrease. The final polycondensation stages are catalyzed by tertiary amines. The amines react with the chloroformate end groups to form intermediate quaternary acylium salts which then react with phenolate to form carbonate and OH ions, hydrolyzing the chloroformate end groups, or to form a urethane in a side reaction [164]. Detailed mechanistic studies of the catalyst reaction were performed by Aquino et al. [173] and Kosky et al. [174]. 

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