Migration of amino groups

The 1,2-migration of amino groups in /3-aminoalkyl radicals such as 24 has also been of interest because of the involvement of these species in the enzyme-catalyzed elimination of ammonia from 1,2-amino alcohols.47-50 These studies have also been reviewed recently by Radom et al45... 

Other rearrangements closely related to this type are those reactions in which there is a migration of amino groups (or atoms at-... 

Acylation of the SH function provides no unequivocal protection, because S-acyl groups can migrate to amino groups. This S - N acyl transfer is not too pronounced in blocking with the S-benzyloxycarbonyl or with the S-tert.butyloxycarbonyl groups, but these possibilities remain to be tested in practice. Somewhat wider application has been reported of the S-ethylcarba-moyl group... 

Fincham, J.K., Shaws, R.A. Phosphrmis-nitrogen crunpounds. Part 62. The reactions of 2,2-diamino-4,4,6,6,8,8-hexachloro- and 2,6-diamino-2,4,4,6.8,8- hexachloro-cyclotetraphospha-zatetraene with sodium methoxide in methanoL The first example of amino group migration in the tetramer system. P, H, and C nuclearmagnetic resonance spectroscopic investigations of the products. Phosphorus, Sulfur and Silicon 47,109-117 (1990)... 

Amino alcohols rearrange in the presence of nitrous acid to give ketones. The intermediate is an aliphatic diazonium salt, and the reactions are concerted and stereo-electronically controlled, with the migration of the group trans-anti to the departing nitrogen. 

Acylation. Reaction conditions employed to acylate an aminophenol (using acetic anhydride in alkaU or pyridine, acetyl chloride and pyridine in toluene, or ketene in ethanol) usually lead to involvement of the amino function. If an excess of reagent is used, however, especially with 2-aminophenol, 0,A/-diacylated products are formed. Aminophenol carboxylates (0-acylated aminophenols) normally are prepared by the reduction of the corresponding nitrophenyl carboxylates, which is of particular importance with the 4-aminophenol derivatives. A migration of the acyl group from the O to the N position is known to occur for some 2- and 4-aminophenol acylated products. Whereas ethyl 4-aminophenyl carbonate is relatively stable in dilute acid, the 2-derivative has been shown to rearrange slowly to give ethyl 2-hydroxyphenyl carbamate [35580-89-3] (26). 

Two disadvantages are associated with the use of S-acetyl or 5-benzoyl derivatives in peptide syntheses (a) base-catalyzed hydrolysis of 5-acetyl- and 5-benzoylcys-teine occurs with /S-elimination to give olefinic side products, CH2=C-(NHPG)CO—(b) the yields of peptides formed by coupling an unprotected amino group in an 5-acylcysteine are low because of prior S-N acyl migration. ... 

The reaction of 3-amino-1,2,4-triazine 1-oxide 1 with methyl iodide in the presence of sodium bicarbonate leads to the methylation of the amino group to afford 3-methylamino-l,2,4-tiiazine 1-oxide 123. This iV-oxide 123, under neutral conditions in the presence of Mel, undergoes methyl group migration to the N(2) atom of the 1,2,4-triazine ring, yielding 3-imino-2-methyl-1,2,4-triazine 1-oxide 124. The same product 124 was obtained by direct methylation of compound 1 under neutral conditions (84TL1677). 

Aminoalcohols are an important class of compounds in medicinal chemistry because many drugs contain this structure. For their resolution, there are two possibilities acylation of amino function or an enzymatic transesterification with vinyl esters through the hydroxyl group. However, the amino or hydroxyl group must be protected, because if the starting material is the free aminoalcohol, the O- and N-acylation can take place, and in addition, there are migrations obtaining... 

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