Primary aromatic amines ring opening

Using primary aliphatic amines, ring opening of isocoumarin-derived thiolactones (3) according to equation (2) offers a convenient access to o-(2-oxoalkyl)thiobenzamides (4) with yields in the 80% range aromatic amines give side reactions. ... 

Cu(BF4)2.xH20 catalyses the ring opening of styrene oxide by amines under solvent-free conditions.22 Primary aromatic amines react regiospeciflcally at the benzyl carbon... 

Wordy Over the past few years, we have encountered numerous examples of water as the perfect solvent. We observed this first in osmium-catalyzed dihydroxylation reactions and also in nucleophilic ring-opening reactions of epoxides. We also observed this in cycloaddition reactions and in most oxime ether, hydrazone, and aromatic heterocycle condensation processes.Finally, we observed it in formation reactions of an amide from a primary amine and an acid chloride using aqueous Schotten-Baumann conditions. ... 

The reactions in Methods A, B and C, which all start from pyrylium salts are analogous to the well-known conversions of 2.4.6-substituted pyrylium salts 27 with ammonia, primary amines, hydrogen sulfide or the anions of CH activated compounds to the corresponding heterocyclic or isocyclic aromatic systems The first step involves addition of the basic phosphine at C-2 (or C-6) to form 2S. Ring-opening, ring-closure and elimination of water are likely steps in the formation of the product 2. 

The amount of catalyst (scandium trisdodecyl sulfate) and ligand, (14), in the ring opening of czT-1,2-disubstituted oxiranes with primary and secondary aromatic amines in water were varied to maximize the yields.33 In all but two cases, the reaction, under ideal conditions, yielded the j3-amino alcohols in >81% yield with enantioselectivity ... 

Many authors elucidated functionalization of polymers containing reactive oxirane moieties. Epoxidized NR, BR, IR and/or the respective model hydrocarbons, poly (butadiene-co-isoprene, various epoxy resins, poly (2,3-epoxypro-pyl methacrylate) and its copolymers or grafted systems were mostly exploited. Stabilizers based on epoxidized unsaturated rubbers are of the top interest. The mechanism of the functionalization process was studied in details by means of 3,4-epoxy-4-methylheptane and 1,2-epoxy-3-ethyl-2-methylpentane as model compounds [289]. The ring opening of the asymmetric oxirane is regiospecific. Aliphatic primary amines attack the least substituted carbon atom and can be involved in crosslink formation. Aromatic primary and secondary amines are less reactive than aliphatic ones because of their lower basicity the attack on the least substituted carbon atom is however preferred too. 

Ammonia and primary aliphatic and aromatic amines convert 4-pyrones into 4-pyridones ° this must involve attack at an a-position, then ring opening and reclosure in some cases ring-opened products of reaction with two mole equivalents of the amine have been isolated, though such structures are not necessarily intermediates on the route to pyridones. The transformation can also be achieved by, first, hydrolytic ring opening using barium hydroxide (see above), and then reaction of the barium salt with ammonium chloride. ... 

When the nucleophile has hydrogen atoms, e.g., with ammonia, primary amines, hydroxylamine, hydrazine derivatives, phosphine, hydrogen sulfide, nitromethane (EWG = NO2), acetonitrile (EWG = CN), an ANRORC (attack by nucleophile, ring opening, ring closure) reaction results in the conversion of substituted pyrylium salts into a large variety of six-membered aromatic carbocyclic or heterocyclic compounds. 

This methodology has also been employed for the preparation of tetradentate ligands by exchanging the primary amines for C2-symmetric primary diamines (eq 4). For example, from (/ ,/ -1,2-diamino-1,2-diphenylethane, diastereomeric ligand B was obtained in 84% yield. These aromatic amines are sufficiently reactive to open the aziridine ring. Due to steric hindrance, no further reaction of the secondary amine moieties with (5)-A -trifluoromethylsulfonyl-2-isopropylaziridine was observed. This tetradentate ligand was inferior to his(sulfonamides) as catalyst... 

The most important applications of peroxyacetic acid are the epoxi-dation [250, 251, 252, 254, 257, 258] and anti hydroxylation of double bonds [241, 252, the Dakin reaction of aldehydes [259, the Baeyer-Villiger reaction of ketones [148, 254, 258, 260, 261, 262] the oxidation of primary amines to nitroso [iJi] or nitrocompounds [253], of tertiary amines to amine oxides [i58, 263], of sulfides to sulfoxides and sulfones [264, 265], and of iodo compounds to iodoso or iodoxy compounds [266, 267] the degradation of alkynes [268] and diketones [269, 270, 271] to carboxylic acids and the oxidative opening of aromatic rings to aromatic dicarboxylic acids [256, 272, 271, 272,273, 274]. Occasionally, peroxyacetic acid is used for the dehydrogenation [275] and oxidation of aromatic compounds to quinones [249], of alcohols to ketones [276], of aldehyde acetals to carboxylic acids [277], and of lactams to imides [225,255]. The last two reactions are carried out in the presence of manganese salts. The oxidation of alcohols to ketones is catalyzed by chromium trioxide, and the role of peroxyacetic acid is to reoxidize the trivalent chromium [276]. 

Pyrylium salts are aromatic heterocycles with an oxygen atom that display a high electrophilic character at the ortho and para positions of the ring. Di- and tri-substituted compounds are fairly stable and have shown to react with primary amines to yield pyridinium salts (Scheme 6.15) [74]. In aqueous solution, the pyrylium form is in equilibrium with the open form (pseudobase ). 

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