Peroxycarbamates

Peroxyesters include the alkyl esters of peroxycarboxyhc acids monoperoxydicarboxyhc acids diperoxycarboxyhc acids monoperoxy- (30) and diperoxycarbonic (31) acids monoperoxy- (32) and diperoxyoxahc (33) acids peroxycarbamic acids (34) peroxysulfonic acids (35) and peroxyphosphoric acids (36). 

Apparently the alkoxy radical, R O , abstracts a hydrogen from the substrate, H, and the resulting radical, R" , is oxidized by Cu " (one-electron transfer) to form a carbonium ion that reacts with the carboxylate ion, RCO - The overall process is a chain reaction in which copper ion cycles between + 1 and +2 oxidation states. Suitable substrates include olefins, alcohols, mercaptans, ethers, dienes, sulfides, amines, amides, and various active methylene compounds (44). This reaction can also be used with tert-huty peroxycarbamates to introduce carbamoyloxy groups to these substrates (243). 

Normally, alkyl peroxycarbamates undergo thermolysis to yield free radicals and carbon dioxide (20). 

The first-order decomposition rates of alkyl peroxycarbamates are strongly influenced by stmcture, eg, electron-donating substituents on nitrogen increase the rate of decomposition, and some substituents increase sensitivity to induced decomposition (20). Alkyl peroxycarbamates have been used to initiate vinyl monomer polymerizations and to cure mbbers (244). They Hberate iodine quantitatively from hydriodic acid solutions. Decomposition products include carbon dioxide, hydrazo and azo compounds, amines, imines, and O-alkyUiydroxylarnines. Many peroxycarbamates are stable at ca 20°C but decompose rapidly and sometimes violently above 80°C (20,44). 

Peroxyesters (1), R(C03 R )n Peroxycarbonicesters (2), ROC(O)—0—0—R Diperoxyesters (3), C(0)(-0-0—R)a Peroxycarbamates (4), >NC(0)-0-0-R Areneperoxysulfonates (5), rso2-o-o-r Difficult to prepare because of ready rearrangement or decompn in polar solvents peroxy sulfonates decomp hetero lyrically (no free radicals) Peroxycarbamates are stable, distillable liqs or cryst solids rapid decompn at 80—140° and violent decompn at 140— 180°. Alkylareneperoxysulfon-ates have low stability and decomp violently at RT within 10 mins... 

In the reaction of an aminoalcohol with a methyl imidazole-AT-carboxylate or tert-butyl imidazole-AT-peroxycarboxylate, selective acylation of the amino function can be achieved11903 to give the carbamate and peroxycarbamate, respectively, the hydroxy groups of which can be further acylated ... 

Alkyl orthophosphate triesters, 79 41 terteAlkyl peroxycarbamates, decomposition of, 78 486 Alkyl peroxyesters, 78 478-487 chemical properties of, 78 480 487 physical properties of, 78 480 primary and secondary, 78 485 synthesis of, 78 478-480 synthetic routes to, 78 479 tert-Alkyl peroxyesters, 78 480 84, 485 as free-radical initiators, 74 284-286 properties of, 78 481-483t uses of, 78 487 Alkylperoxy radical, 74 291 Alkyl phenol ethoxylates, 8 678, 693 ... 

Peroxyeslerx include the alkyl esters of peroxycarboxylic acids tnonoper-oxydicarboxylic acids diperoxycarboxylic acids monoperoxy- (24) and diperoxycarhonic (25) acids monoperoxy- (26) and diperoxyoxalic (27) acids peroxycarbamic acids (28) peroxysulfonic acids (29) and perox-yphosphoric acids. 

Attempts have also been made to use a combination of copper salts and bisoxa-zolines, and other chiral ligands, for the amination reaction using A-(p-toluenesul-fonyl)peroxycarbamate as the nitrogen source, but the yield and ee of the allyl amines obtained were generally low [42]. 

Peroxycarbamic acid derivatives are very reactive epoxidizing agents that can be employed under mild conditions and are practically independent of the solvent effect examples are the reagent (probably 40) prepared from carbonylditriazole with H2O2 and A-benzoylperoxycarbamic acid The latter is very useful for... 

The yields of epoxides are 35-70% the yields of 1,3-diphenylurea are 92-98%. Yields of epoxides are improved by use of nonpolar solvents such as n-pentane or benzene. p-Chlorophenyl isocyanate gives somewhat higher yields than phenyl isocyanate. The active intermediate is probably an isocyanate-hydrogen peroxide complex rather than a peroxycarbamic acid (CgHsNHCOgH).1 N. Matsumura, N. Sonoda, and S. Tsutsumi, Tetrahedron Letters, 2029 (1970)... 

Other approaches to free-radical polymers Include capping with a peroxy end group or using a dual path initiator. The former approach was used (65) to convert a,(o-hydroxy polyethers (Eth) to esters to peroxycarbamate end groups (Reaction 19) ... 

Acyl nitrites Enisocy anates N-Hydroxyurethans Peroxycarbamic acids... 

C-Nitrosoformic acid esters Peroxycarbamic acids and esters... 

Bis-peroxycarbamates [hexamethylene-JV,/Vhis(feft-butylperoxycarbamate) or HBTBP, and methylene bis-4-cyclohexyl-/VX(teft-butylperoxycarbamate), or MBTBP] [30]... 

There are two possible crossUnking mechanisms which occur in the presence of those peroxycarbamates (Schemes 6 and 7) [30]. One is different from the usual mechanism of diamine crosslinking, while the second one is the classic one where the diamine adds onto the polymeric backbone by nucleophilic Michael addition. Indeed, those peroxycarbamates can undergo a thermal decomposition creating radicals (Scheme 6), and so the crosslinking mechanism can be a nucleophilic addition. 

Scheme 6 The homolytic thermal decomposition of the hexamethylene-N,N bis(tert-butyl) peroxycarbamate [30]...

In the crosslinking formation by HBTBP, there is a thermal decomposition of the peroxycarbamates to give free radicals in a suitable medium. This thermal decomposition is represented in Scheme 6 [30,126-129]. 

Finally, it was deduced that the crossUnking mechanism for aliphatic and aromatic containing amine and diamine was slightly the same and took place in three steps. Aliphatic diamines are more reactive than aliphatic amines and the most used diamine is HMDA-C and its derivatives (N,N -dicinnamyfidene-l,6-hexanediamine and bis-peroxycarbamates). During the post-cure treatment, two different mechanisms of bond making and bond breaking were evidenced, as explained in Sect. 3.1.4. 

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