Aza-heterocycles

Quinoxalines undergo facile addition reactions with nucleophilic reagents. The reaction of quinoxaline with allylmagnesium bromide gives, after hydrolysis of the initial adduct, 86% of 2,3-diallyl-l,2,3,4-tetrahydroquinoxaline. Quinoxaline is more reactive to this nucleophile than related aza-heterocyclic compounds, and the observed order of reactivity is pyridine < quinoline isoquinoline < phenan-thridine acridine < quinoxaline. ... 

Zimmermann SC, Lawless LJ (2001) Supramolecular Chemistry of Dendrimers. 217 95-120 Zwanenburg B, ten Holte P (2001) The Synthetic Potential of Three-Membered Ring Aza-Heterocycles. 216 93-124... 

The Synthetic Potential of Three-Membered Ring Aza-Heterocycles... 

During our research in this field of small-ring heterocycles we found that functionahzed aziridines are attractive chiral catalysts, e.g., in the diethylzinc addition to aldehydes. Aspects of such uses of aziridines will be discussed as well. This overview does not pretend to be an exhaustive coverage of all existing literature on small-ring aza-heterocycles as that would require a separate monograph. Instead, emphasis is put on functionahzed three-membered aza-heterocycles, that were investigated in the author s laboratory [1], and relevant related literature. The older literature on these heterocycles is adequately summarized in some extensive reviews [2]. Chiral aziridines have been reviewed recently by Tanner [3], by Osborn and Sweeney [4], and by McCoull and Davis [5]. 

Azirines are the most strained three-membered aza-heterocycles. Remarkably, these highly strained types of molecules occur in nature, namely azirino-mycin 14 and dysidazirine 15 (Fig. 1). 

Yamanchi T, T Handa (1987) Characterization of aza heterocyclic hydrocarbons in urban atmospheric particulate matter. Environ Sci Technol 21 1177-1181. 

Grubbs and coworkers [238] used the ROM/RCM to prepare novel oxa- and aza-heterocyclic compounds, using their catalyst 6/3-15 (Scheme 6/3.9 see also Table 6/3.1). As an example, 6/3-35 gave 6/3-36, by which the more reactive terminal alkene moiety reacts first and the resulting alkylidene opens the five-membered ring. In a similar reaction, namely a domino enyne process, fused bicyclic ring systems were formed. In this case the catalyst also reacts preferentially with the terminal alkene moiety. 

Representative of recent applications of the reaction to the synthesis of heterocycles are the photodehydrochlorination of chlorobenzo[b]thiophen (347) to give the fused pyrimidone 348,287 the photoelimination of HI from iodobenzene derivatives 349 to give the benzazepines 350,288 and the synthesis of the medium ring aza-heterocycle 351 by irradiation of the chloro precursor 352.289 Included among the many other examples of... 

Related microwave-assisted ring-closing metathesis reactions, leading to seven-[154] and eight-membered aza-heterocyclic products [49], are depicted in Scheme 6.74. 

Starting Materials Containing One Five-Membered Aza Heterocyclic Ring 375... 

Starting Materials Containing One Six-Membered Aza Heterocyclic Ring 382... 

Reductive amination is used in most of the syntheses as the method for the formation of a five- or six-membered aza heterocyclic ring. A triple reductive amination approach to castanospermine and swainsonine has been reported by Mootoo et al. <2001JOC1761> (Scheme 56). 

Recent research deals with stereoselective 1,3-dipolar cycloadditions of nitrones for the syntheses of alkaloids and aza heterocycles asymmetric synthesis of biologically active compounds such as glycosidase inhibitors, sugar mimetics, /3-lactams, and amino acids synthesis of peptido-mimetics and peptides chemistry of spirocyclopropane heterocycles synthesis of organic materials for molecular recognition and photochemical applications. 

Sawicki, E., S. P. McPherson, T. W. Stanley, J. Meeker, and W. C. Elbert. Quantitative composition of the urban atmosphere in terms of polynuclear aza heterocyclic compounds and aliphatic and polynuclear aromatic hydrocarbons. Int. J. Air Water Pollut. 9 515-524, 1%5. 

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