Heterocyclic amine precursors

A further example of homoleptic Tc complexes with heterocyclic amines is provided by the dicationic complex [Tc(bipy)3] " " (531). Starting from the Tc precursor... 

The most important applications of the in situ photochemical fluorodediazoniation start from heterocyclic amines for which the diazonium tetrafluoroborates are impossible to isolate. In this way, fluorinated imidazoles,123-253,254-257 261 benzimidazoles,262 pyrazoles,254-256,262 indazoles,158 thiazoles,259 and triazoles259-262 have been prepared (Table 4). Some of these are the precursors of biologically active compounds such as fluoro-substituted histidines or histamines,123,253-257,258 or 5-fluoro-l/ -D-ribofuranosylimidazole-4-carboxamide.261... 

Knize, M.G. and Felton, J.S. (2005) Formation and human risk of carcinogenic heterocyclic amines formed from natural precursors in meat. Nutr. Rev., 63,158-165. 

Of the components in the various lists, the four classes of tobacco smoke components investigated in greatest detail during the past five decades were the PAHs, aza-arenes, NNAs, and the V-heterocyclic amines. Because of the wealth of background information available on PAHs demonstrated to be tumorigenic in laboratory animals, extensive research (isolation, identification, quantitation, precursors, removal, prevention of formation, etc.) was conducted in the 1950s and... 

Isatin-3-imines 822 are versatile precursors for the synthesis of spiroheterocycles. They were prepared by grinding together an equimolar mixture of isatin and aromatic or heterocyclic amine. Subsequent treatment with mercaptoacetic acid using inorganic supports such as montmorillonite KSF, alumina, or silica gel in an open vessel upon MWI gave spiro compounds 823 within 5-7 min. The montmorillonite KSF is the best solid support, giving the best yields (92-97%) in the shortest time and easiest work-up (Scheme 156) (030PP401). 

NHC (N-Heterocyclic Carbene) precursor is prepared by established procedtrres from 2 mols of amine, 1 mol of glyoxal and one mol of formaldehyde [Arduengo USPatent 5 077 414 1991, Chem Abstr 116 106289 1002, cf Hermarm et al. Chem Eur J 2 1627 1996] and washed with THF before use. It is useful for making IMesCuCl which in turn is used for making IMesAuCl and [IMesPtCl]2 [Furst Casin Chem Commun 46 6924 2010],... 

Numerous substituted p pmidine and tiiazine amines have found utility as precursors to highly active and crop selective sulfonylurea herbicides. In the process of optimizing herbicidal efficacy and crop safety within this class, a variety of structurally diverse heterocyclic amines have been synthesized and evaluated. This paper reviews the methods of preparation that have been developed for some of the different structural types used as intermediates to active sulfonylurea herbicides. These methods include cyclizations, rearrangements, and side-chain metalations that have led to furo[2,3-d]pyriiindines, pyrazinones, and selectively functionalized pyrimitoes, triazines, triazoles, and pyridines. 

Silver ( Ag) (f=l/2, 1/2). Silver-containing layered networks [Ag(L)] (L = 4-pyridinesulfonate or p-toluenesulfonate) were treated with primary amines in different ratios. Solid-state ° Ag, and CP/ MAS NMR experiments were used to study the interactions between the primary amines and the parent materials. Ag chemical shift tensor parameters are extremely sensitive to changes in silver environments. Reaction of Ag20 with the A-heterocyclic carbene precursors 3,5-bis[3-(2,4,6-tri-methylphenyl)imidazolium-l-ylmethyl]-lH-pyrazole bishexafluorophosphate and 3,5-bis[3-(2,6-diisopropylphenyl)imidazolium-l-ylmethyl]-lH-pyrazole bishexafluorophosphate yielded silver(I) complexes 2 and 3, respectively The identity of those species could be elucidated by detailed NMR spectroscopic studies ( H, C, N, Ag and DOSY experiments). 

Sheremetev and co-workers employed diazo compounds of type 60, prepared from the corresponding amines in moderate yields as alternative excellent precursors for the preparation of side-chain-functionalized derivatives (Scheme 29). Several furazans bearing reactive groups or cyclopropyl or five-membered heterocyclic substituents have been prepared by standard procedures (99MI6). 

The Ugi reaction is the four-component condensation of an amine, aldehyde or ketone, carboxylic acid and isocyanide to give an o -acylamino amide [22-24], Although this process has the potential to introduce considerable diversity, the products themselves are not heterocycles but through appropriate choice of substrates, latent functionality in one of the precursors can intercept either an intermediate or further derivatize the acylamino amide Ugi product through post-modification. Thus variants of the Ugi reaction have been investigated under microwave-assisted conditions for the synthesis of diverse heterocyclic libraries [16,19-24],... 

Organolanthanides are catalyst precursors for the formation of five-, six-, and even seven-membered heterocycles. These IHs are also effective with secondary and aromatic amines (e.g. Eq. 4.20). 

The silicon containing (5 5 5) heterocycle 32 has been efficiently synthesized starting from. Y-prolinc 375 via silanes 376, 378, and 379. The final step has been achieved via radical cyclization. The amine 377 was treated with COCl2 and the resulting carbamoyl chloride 378 reacted with PhSeNa to give the radical precursor 379 (84% overall yield from 376). Compound 379 when refluxed with Ph3SnH or Bu3SnH in the presence of AIBN afforded the desired heterocycle 32 in 75% yield (Scheme 81). 

Heterocycles can be employed as precursors for the synthesis of pyrazoles. Pyrazoles can be synthesized by three-membered ring substrates. For example, allyl amines 12 and pyrazoles 13 could be obtained by hydrazinolysis of 2-ketoaziridines 11 <06TL255>. Regioselective ring opening of 3-aryl-2-benzoyl-l,l-cyclopropanedicarbonitriles 14 with hydrazine provided a new process for the synthesis of 5-aryl-3-phenylpyrazoles 15 <06JHC495>. 

---