White deamination

The White deamination procedure has been used in the tran.sformation of the steroidal alkaloids tomatidine (1) and solasodine into dihydroneotigogenin (4) and dihydrotigogenin, respectively. Thus (1) was converted into the N,22-dihydride... 

Oxidation of amides (White deamination) [follows 1, 327], White223 has described the benzoylatien of 2-phenylethylamine (1), the reaction of (2) with dinitrogen tetroxide to give (3), which on thermal decomposition at 77° affords 2-phenylethyl benzoate (4). 

Wharton reaction 17, 937 White deamination 15, 269 Wibaut s. Arens Wideqvist reaction 3, 684 Wiechell s. Fritsch Wieland s. Barbier Willgerodt-Kindler reaction... 

As Figure 1 depicts, phenylalanine ammonia-lyase (PAL), which occurs ubiquitously in higher plants and the wood-rotting Basidiomycetes (1-3), seems to play a common central role in the conversion of phenylalanine (by deamination) to a wide variety of secondary metabolites. These include lignins in higher plants (4), veratryl alcohol in the white-rot fungus Phanerochaete chrysosporium (4a), and methyl p-anisate in the brown-rot fungus... 

Yakovenko, B.V. and Yavonenko, A.F. (1991). The influence of acclimation temperature on the rate of glycine deamination in white muscle and hepatopancreas of carp (InRussian). GidmbiologicheskiiZhumal27(3), 111. 

Deamination of primary aliphatic amino groups in (suitably substituted) peptides may also be possible via diazonium fluoborates and triazenes (White and Scherrer, 1961) ... 

Because of the basicity of the hydroxide counter-anion, diazonium ions formed in deamination can be expected to be particularly susceptible to anion exchange by the proton-transfer mechanism described above. White has shown that the deamination of optically active 2-phenyl-2-butylamine in acetic acid yields alcohol with 74% retention of configuration and acetate with 61% retention, together with a small amount of nitrite. He points out that the formation of acetate and nitrite are readily explained by proton exchange between the hydroxide ion and molecules of acetic and nitrous acid. As is expected, the product of collapse with the original counter anion shows the least amount of racemization (White and Stuber, 1963). Similar results have been obtained by Huisgen and Ruchardt (1956b) for the deamination of optically active -phenethylamine. 

Whiting has reported product analyses on the rearrangement of cis-and secondary acyclic systems. For the fmws-phenyltriazene, however, as much as 24% of RX was obtained. In this connection, the nearly identical stereochemistry of the acetates obtained from the deamination and nitrosoamide rearrangement of a-phenylethylamine in acetic acid (White and Stuber, 1963) may also be mentioned. 

Deamination Aryidiazonium hexafluorophosphates. Aryldiazonium tetrahaloborates. Di-fluoroamine. Dinitrogen tetroxide (White). Hydroxylamine-O-sulfonic aeid. Hypophos-phorous acid. 3-Nitro-N-nitrosocarbazole. Nitrosyl chloride. Tetramethylurea. Debenzylation of benzoylamines Triethyloxonium fluoroborate. 

Anhydrous piperazine is a white solid which is obtained as leaflets when crystallised from alcohol, m.p. 106°C (b.p. 145-146 C). Piperazine may be prepared by several methods [40], However, industrially it is best prepared by cyclodehydration of 2-hydroxyethylamine (34) or N-(2-aminoethyl)-2-hydroxyethylamine (35) at high temperatures in the presence of a catalyst like Ra-Ni and habdes of Zn, Fe, A1 or Mg [41-43]. Catalytic deamination of diethylenetriamine (36) in the presence of Ra-Ni catalyst in an autoclave at 150°C also gives piperazine. Another useful method to prepare piperazine involves reduction of pyrazine (37) by sodium and ethanol [40] (Scheme 1). 

White, E.H. and N. Egger (1984). Reaction of syd-nones with ozone as a method of deamination On the mechanism of inhibition of monoamine oxidase by sydnones. J. Am. Chem. Soc. 106, 3701-3703. 

For some other nitroso compounds and related reagents developed by White for the deamination of alkylamines in organic solvents, see White et al., 1992b, refs. 3-7. 

The l-alkyl-3-aryltriazenes (7.15 see Scheme 7-3) are easily obtained from aromatic diazonium salts and alkylamines. They exist in a tautomeric equilibrium (see Zollinger, 1994, Sect. 13.4) and, under acid catalysis, they dissociate into both possible combinations of amine and diazonium ion. The aliphatic amine and aromatic diazonium ion will, however, react further with each other, whereas in the combination alkanediazonium ion -h aromatic amine the diazonium ion will decompose rapidly into the carbocation and dinitrogen. This system has been used little for mechanistic or preparative deamination studies, obviously because a very complex product pattern is inherent in it. The carbocation may react with the aromatic and the aliphatic amine at the amino group. A modified method was described by Southam and Whiting (1982) using anhydrous acetonitrile as medium at —10 to -5°C. ... 

Although this reaction does not lead to an alkanediazonium ion, it is obvious that it is another method that is closely related to the deamination pathways discussed in this section. The azoxytoluenesulfonate method is related to the use of N-nitroamides as a source for carbocations because the leaving group is also nitrous oxide (7-10). The A -nitroamide decomposition was used extensively by White and coworkers in the 1960 s and 1970 s (see White and Grisley, 1961 White et al., 1973 White and Field, 1975, and literature cited there). N-Nitro carbamates (7.25, R = OR") can also be used. 

We have reviewed the early history of primary aliphatic amine deaminations up to the 1950 s in Section 7.1. The mechanisms that were postulated and evaluated until the late 1960 s or mid-1970 s have been discussed by various authors (White and... 

Table 7-2. Deamination intermediates and products of 1-amino-1-phenylethane derivatives in di-oxane at 25°C after White et al. (1992 b), R = 2-naphthyl.

The reader who is not well acquainted with the extensive and controversial literature of deamination mechanisms of the last five decades may have the impression from our relatively detailed review of White et al. s recent paper and of the related work of Collins group that the dominant role of ion pairing in deaminations was not clearly recognized earlier. This is by no means the case. The paper of White s group (1992b) was chosen for this discussion because it combines and expands previous partial results with 1-phenylethylamine derivatives for which mechanistic conclusions are not disguised by a multitude of products as they are illustrated in the introductory Scheme 7-1. 

The inert molecule-separated ion pair formation in Scheme 7-17 may be regarded as a two-fold dissociation of R —N2 —OCOR, giving successively the diazonium ion-counterion pair (R — OCOR ) and the separated ion pair (R+ N2 OCOR ), or it may be a concerted decomposition, leading directly to (R" N2 OCOR ). Southam and Whiting (1982) presented arguments for the second alternative in deaminations of octane-4-amine based on internal-external product ratios for A/-nitroso butanamide solvolyses in acetic acid. That explanation is, however, falsified by the results of Fishbein s group discussed earlier in this section ... 

The most extensive investigation on the deamination of trans- and cis-4- tert-butyl)cyclohexylamine (7.89 and 7.90, respectively) by the three procedures mentioned was conducted by Whiting s group (Maskill et al., 1965 Maskill and Whiting, 1976) in acetic acid (in part in butyric acid). 

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