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. ... 

Aluminum chloride [7446-70-0] is a useful catalyst in the reaction of aromatic amines with ethyleneknine (76). SoHd catalysts promote the reaction of ethyleneknine with ammonia in the gas phase to give ethylenediamine (77). Not only ammonia and amines, but also hydrazine [302-01-2] (78), hydrazoic acid [7782-79-8] (79—82), alkyl azidoformates (83), and acid amides, eg, sulfonamides (84) or 2,4-dioxopyrimidines (85), have been used as ring-opening reagents for ethyleneknine with nitrogen being the nucleophilic center (1). The 2-oxopiperazine skeleton has been synthesized from a-amino acid esters and ethyleneknine (86—89). 

The diazotization of amino derivatives of six-membered heteroaromatic ring systems, particularly that of aminopyridines and aminopyridine oxides, was studied in detail by Kalatzis and coworkers. Diazotization of 3-aminopyridine and its derivatives is similar to that of aromatic amines because of the formation of rather stable diazonium ions. 2- and 4-aminopyridines were considered to resist diazotization or to form mainly the corresponding hydroxy compounds. However, Kalatzis (1967 a) showed that true diazotization of these compounds proceeds in a similar way to that of the aromatic amines in 0,5-4.0 m hydrochloric, sulfuric, or perchloric acid, by mixing the solutions with aqueous sodium nitrite at 0 °C. However, the rapidly formed diazonium ion is hydrolyzed very easily within a few minutes (hydroxy-de-diazonia-tion). The diazonium ion must be used immediately after formation, e. g., for a diazo coupling reaction, or must be stabilized as the diazoate by prompt neutralization (after 45 s) to pH 10-11 with sodium hydroxide-borax buffer. All isomeric aminopyridine-1-oxides can be diazotized in the usual way (Kalatzis and Mastrokalos, 1977). The diazotization of 5-aminopyrimidines results in a complex ring opening and conversion into other heterocyclic systems (see Nemeryuk et al., 1985). 

Sulfur atom as internal nucleophile. In this area, it has been shown that the reaction of 8-bromo-l,3-dimethyl-7-(2,3-epithiopropyl)xanthine 147 with a range of aliphatic and aromatic amines generates efficiently 2-amino-substituted 2,3-dihydro-thiazolo[2,3-/]xanthine derivatives 148. The process involves a sequential amine-induced thiirane ring opening followed by thiolate z/MYi-substitution of chlorine atom (Equation 66) <1994PCJ647>. 

Carree, F. Gil, R. Collin, J. (2004) Samarium iodides catalyzed meso-epoxides ring opening by aromatic amines.. Tetrahedron Lett., 45 7749-7751. 

Azoulay, S. Manabe, K. Kobayashi, S. (2005) Catalytic asymmetric ring opening of meso-Epoxides with Aromatic Amines in Water., Org. Lett, 14593-4595. 

Kureshy, R. 1. Singh, S. Khan, N. H. Abdi, S. H. R. Agrawal, S. Mayani, V. J. Jasra, R. V. (2006) Microwave-assisted asymmetric ring opening of meso-epoxides with aromatic amines catalyzed by a Ti-S-(—)-BlNOL complex.. Tetrahedron Lett., 47 5277- 5279. 

Gao, B. Wen, Y. Yang, Z. Huang, X. Liu, X. Feng X. (2008) Asymmetric ring opening of meso-Epoxides with aromatic amines catalyzed by a new proline-based N,N -dioxide-indium tris (triflate) complex,/t/v. Synth. Catal, 350 385- 390. 

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 treatment of thiurets (diimino-l,2,4-dithiazolidines, (297)) with aromatic amines results in ring opening to form thiocarbamylguanidines (298) and sulfur cyclization to 3,5-diamino-1,2,4-thiadiazole derivatives (299) can occur spontaneously or upon oxidation (Scheme 67) <84CHEC-1(6)463 >. 

A unique acyclic C-nucleoside containing the pyrido[2,3-. ]pyrazine nucleus 675 was prepared by the action of AcOH, whereby rearrangement of 3 -keto-2 -deoxypyrazine C-nucleoside derivatives 673 occurs via the intramolecular aminal intermediate 674, followed by furanose ring opening and subsequent aromatization (Equation 56)... 

Figure 3.5 The synthesis of diazepam is initiated by the double acylation of an aromatic amine with an aromatic acid chloride. A second equivalent of the p-chloroaniline leads to a six-membered ring with two nitrogens. This is hydrolytically opened to expose a free amino group which reacts with an aminoester to yield a seven-member ring. The amide nitrogen is then methylated.

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. 

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