Amino groups types

The 3-amino group brings a second nucleophilic center in these structures thus 2-imino-3-amino-4-methyl-4-thia201ine (409) reacts with methyl diloroformate to give the bicyclic compound (410) (Scheme 234). Other thiazolo-s-triazoles of the [3.2-l>] type have been obtained by... 

Compounds of this type possess a definite Aj-selenazoline structure, while homologous compounds with at least one labile hydrogen on the 2-amino group can exist as a tautomeric equilibrium (Scheme 64). 

There are two distinct groups of aldolases. Type I aldolases, found in higher plants and animals, require no metal cofactor and catalyze aldol addition via Schiff base formation between the lysiae S-amino group of the enzyme and a carbonyl group of the substrate. Class II aldolases are found primarily ia microorganisms and utilize a divalent ziac to activate the electrophilic component of the reaction. The most studied aldolases are fmctose-1,6-diphosphate (FDP) enzymes from rabbit muscle, rabbit muscle adolase (RAMA), and a Zn " -containing aldolase from E. coli. In vivo these enzymes catalyze the reversible reaction of D-glyceraldehyde-3-phosphate [591-57-1] (G-3-P) and dihydroxyacetone phosphate [57-04-5] (DHAP). 

This type of cyclization is important only for the formation of cinnolines. In all cases, the starting compounds have an ortho amino group, which upon diazotization undergoes ring closure with the other functionality, most frequently with a multiple bond. 

The employment of non-protic electrophiles for the foregoing type of cyclizations as illustrated in Scheme 8 has the particular merit of leaving a useful point of departure for further transformations. Comparable cyclizations of 2-allyl-3-aminocyclohexenones with mercury(II) acetate are preceded by dehydrogenation to the corresponding 2-allyl-3-aminophenol as shown in Scheme 9 82TL3591). The preferred direction of cyclization depends upon the nucleophilicity of the amino group. 

Canonical forms of type (442b) facilitate proton loss from the amino groups the anions formed react easily with electrophilic reagents, usually preferentially at the exocyclic nitrogen atom e.g. 443 -> 444) (79HC(34-2)9). 

Substituents in the indazole ring may direct a given reaction towards another position either by their R and I electronic properties or simply by protecting the most reactive position. Examples of both types are found in sulfonation studies (67HC(22)l). As indicated before (Section 4.04.2.3.2(i)), sulfonation takes place at position 7. However, the presence of an amino group at positions 5 or 7 directs the attack towards the 4-position (Scheme 40). To obtain the indazole-5-sulfonic acid a more complicated procedure has been used but it is still based on the same ideas. 

Another type of bifunctional catalysis has been noted with a,cn-diamines in which one of the amino groups is primary and the other tertiary. These substituted diamines are from several times to as much as 100 times more reactive toward imine formation than similar monofunctional amines. This is attributed to a catalytic intramolecular proton transfer. 

Physostigmine can be regarded as the methylcarbamate of a -amino-phenol, with an alkyl chain substituent in the o-position, relative to the amino-group. Stevens and Beutel, with this in mind, have prepared substances of the type p-RjRjjN, CO, O. CgHjR. NMCjX, where R is an alkyl radical, c.gi, isopropyl, in either the o or m-positioQ relative to the... 

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