Fris amine

The less hindered f/ans-olefins may be obtained by reduction with lithium or sodium metal in liquid ammonia or amine solvents (Birch reduction). This reagent, however, attacks most polar functional groups (except for carboxylic acids R.E.A. Dear, 1963 J. Fried, 1968), and their protection is necessary (see section 2.6). 

The mechanism of NPYR formation has been studied by Coleman (37) and Bharucha et al. ( ). Coleman (37) reported that the requirement for a high temperature, the inhibitory effects of water and antioxidants, and the catalytic effect of a lipid hydroperoxide are consistent with the involvement of a free radical in the formation of NPYR. Similarly, Bharucha et al. (29) suggested that, since both NPYR and NDMA increase substantially towards the end of the frying process, N-nitros-amine formation during frying of bacon occurs essentially, if not entirely, in the fat phase after the bulk of the water is removed and therefore by a radical rather than an ionic mechanism. These authors speculated that, during the frying of... 

Smoking. The effects of smoking on the formation of N-nitros-amines in bacon has been investigated recently by Bharucha et al. ( ). They reported that unsmoked bacon samples generally tended to contain more N-nitrosamines, presumably because of their higher nitrite content at the time of frying. Sink and Hsu (55) showed a lowering of residual nitrite in a liquid smoke dip process for frankfurters when the pH also was lowered. The effects of smoke seem to be a combination of pH decrease and direct C-nitrosation of phenolic compounds to lower the residual nitrite in the product (56). This is an area which requires further study since certain C-nitrosophenols have been shown to catalytically transnitrosate amines in model systems (57). 

Fry and Newberg 1,2> examined the electrochemical reduction of nor-camphor oxime (109) and camphor oxime (110) to the corresponding amines. The results of this study are shown in Table 3. It is clear from a comparison of these data with those in Table 2 that the electrochemical reduction of oximes 109 and 110 takes a very different stereochemical course from reduction of the corresponding anils 103 and 104. Reduction of oximes apparently proceeds under kinetic control, affords products corresponding to protonation at carbon from the less hindered side of the carbon-nitrogen double bond, and affords the less stable epimeric amine in each case. It is not evident why the stereochemistry of reduction of anils and oximes should differ, however. 

Arylamine Photodecomposition. A number of researchers have alluded to the fact that the products produced from photolysis of aromatic carbamates (i.e., la) also degrade upon irradiation (10), 17). Indeed, we found that the aryl amine 2b and the photo-Fries products 2c and 2d (resulting from photolysis of 2a) decomposed with respective disappearance quantum yields of 0.035, 0.004, and 0.003 when irradiated at 280 nm. These latter results agree with those of Schwetlick et al. (17), who found the rates of disappearance of lc and Id to be quite small. 

The results in this paper support an N-C bond cleavage mechanism (Schemes I and II) for the photolysis of both TDI and MDI based polyurethanes. The substituted anilinyl radicals observed no doubt are formed by diffusion from a solvent cage after the primary N-C bond cleavage. Although not specifically shown in this paper, the reported photo-Fries products (6) are probably formed by attack of the carboxyl radical on the phenyl ring before radical diffusion occurs. The solvent separated anilinyl radicals rapidly abstract hydrogens from the solvent to give the reported aromatic amine product (6). 

Presently about 20 different mutagenic and/or carcinogenic heterocyclic amines (HAs) have been isolated from various heat-processed foods. One class of these HAs is formed by pyrolysis of proteins or some amino acids. These HAs are amino-carbolines (Figure 13.7), and have been identified in grilled, broiled, baked, and fried meat and fish products, in meat sauces and bouillons, as well as in pyrolyzed proteins, glutamate, lysine, phenylalanine, tryptophan, ornithine, and creatine. 

Meats, charbroiled, smoked, or fried Many, largely polycycUc aromatic hydrocarbons such as benzo[a]pyrene, and heterocyclic amines... 

Dialkylquinazolines 825 are available by microwave-assisted amination and ring closure of 2-acylamino phenyl-ketones 824 with ammonium formate <20070L69>. The 2-aminophenyl ketone precursors of the amides 824 are available by a photochemically induced Fries rearrangement of anilides 823, which enables a variety of different alkyl substituents to be incorporated at the 4-position of the quinazoline <20070L69>. 

This type of duality of action is presumably present in other situations, such as the Fries rearrangement (78), the Friedel-Crafts reaction with acid chlorides (65) or acid anhydrides (21), and the catalytic chlorination of nitrobenzene (17). In these reactions it appears that the uncoordinated Lewis acid is the effective catalyst. The same situation is illustrated by recent work on aromatic amination (32, 33) and halogenation (57, 58, 71) and seems to be general feature of Lewis acid-catalyzed electrophilic reactions of aromatic compounds containing suitable donor groups. 

Hwang et al. developed a rapid and sensitive HPLC-UV method for the analysis of nine derivatized BAs, with benzoyl chloride as the derivatization agent. The reaction is faster than with tosyl chloride and leads to stable products with shorter elution times than do dansyl derivatives. The amines were previously extracted after acidification with TCA. The method was applied to detect BAs in fried marlin fillet, implicated in a food poisoning incident (in Taipei City in 1996) and indicated that a high level of His (84.1 mg/100 g) was present in the sample (80). 

O-Phthaldialdehyde (OPA) is an amine detection reagent that reacts in the presence of 2-mercaptoethanol to generate a fluorescent product (for preparation, see Section 4.1, 2-mercaptoethanol) (Fig. 91). The resultant fluorophore has an excitation wavelength of 360 nm and an emission point at 455 nm. OPA can be used as a sensitive detection reagent for the HPLC separation of amino acids, peptides, and proteins (Fried et al., 1985). It is also possible to measure the amine content in proteins and other molecules using a test tube or microplate format assay with OPA. Detection limits are typically in the microgram per milliliter range for proteins. 

This reaction scheme was later confirmed for the reduction of oximes in acidic solution by isolation of the intermediate ketimine in two cases 143-). However, in alkaline medium, reduction of the C=N bond in oximes and semicarbazones pre-ceds splitting of the N-Y bond, so that hydroxylamines and hydrazines may be obtained144 The stereochemistry of the electrochemical and chemical (H2/Pt, Na/EtOH) reduction of several imines to amines has been compared recently by Fry and Reed 144b ... 

In the diaryl amine series 191 (Scheme 47), additional, synthetically valuable, anionic pathways provide routes to anthranilates 190, oxindoles 192, and dibenzazepinones 194. Although not explored in terms of its scope [75c], the lateral metalation-cydization, 191 -> 192, is extensively precedented [69] but harbors intriguing potential for subsequent DreM chemistry. The rearrangement 191 —> 190 is an N —> ortho C anionic Fries equivalent of the aryl O-carbamate migration (Scheme 3E) [75c] and after N-methylation, 190 may be transformed into 1,2,3-trisubstituted systems 193 [76]. In another appealing manifestation of CIPE, the efficient conversion of 191 into dibenzazepinone 194 has been applied in an effective synthesis of the antiepileptic drug oxcarbazepine (Trileptal ) 195 [77] and may also be... 

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