Nitrogen, substitutional

Zugravescu reports the isolation of ring nitrogen substitution products (195) (Scheme 124) (325). and it is not clear whether direct electrophilic substitution in the 5-position is the general case or if the finally observed product results from rearrangement. 

Hydroxypyrroles. Pyrroles with nitrogen-substituted side chains containing hydroxyl groups are best prepared by the Paal-Knorr cyclization. Pyrroles with hydroxyl groups on carbon side chains can be made by reduction of the appropriate carbonyl compound with hydrides, by Grignard synthesis, or by iasertion of ethylene oxide or formaldehyde. For example, pyrrole plus formaldehyde gives 2-hydroxymethylpyrrole [27472-36-2] (24). The hydroxymethylpyrroles do not act as normal primary alcohols because of resonance stabilization of carbonium ions formed by loss of water. 

The nitrogen substitution chemistry of 2,3-dichloro-l,4-naphthoquiaone (30) has been widely employed (101). Although the product mixtures are sometimes complex, many examples illustrate the excellent results possible ia specific iastances eg, 3-nitro-12JT-ben2o[b]phenoxa2iae-6,ll-dione... 

A compound in which the —OH group of an acid is replaced by —NH2 is called an amide. When the —OH is replaced by —NHR, the product is called a nitrogen-substituted amide or, abbreviated, an N-substituted amide. One way to make amides is to react ammonia (or an amine) with an ester ... 

Reaction of A,A-dimcthylsullamoyl aziridines 323 and 325 with primary amines furnishes substituted 1,2,5-thiadiazolidine 1,1-dioxides 324 and 326, respectively, in a regioselective manner <06SL833>. Aziridine 325 is made from ( I /t,6,S ,Z)-bicyclo[4.2. l]non-3-en-9-one in two steps /V,/V-dimethylsulfamoyl imine formation using dimethylsulfamide and subsequent reaction with trimethylsulfoxonium ylide. The product from the reaction with 4-methoxy-benzyl amine can be subsequently manipulated (debenzylation and derivatization) to give the alternative nitrogen substitution pattern in a controlled manner. 

Effects of nitrogen substitution can be predicted by quantum chemical calculations (42,43), or more qualitatively by examining the charge distribution in the relevant carbocations. When a carbocation is generated at C-l, the positive charge can be delocalized as shown below. 

The results of studies of the acid-catalyzed hydration of oxygen-, sulfur-, seleno-and nitrogen-substituted alkenes and the relevance of this work to partitioning of the corresponding carbocation intermediates (Chart 1) between deprotonation and nucleophile addition was reviewed in 1986.70. We present here a brief summary of this earlier review, along with additional discussion of recent literature. 

Kuhn EP, Suflita JM (1989) Anaerobic biodegradation of nitrogen-substituted and sulfonated benzene aquifer contaminants. Hazard Waste Hazard Mater 6(2) 121-134... 

The drawback of this reaction is its extremely high sensitivity to the steric bulk of the nitrogen substitutent. When the analogous /V-benzylimine 101 was subjected to the standard hydrosilylation conditions, the reaction gave 55% conversion and 47% ee with prolonged reaction time (96 hours). A practical way to overcome this problem is to employ a nucleophilic promoter to convert the intermediate into a more reactive species. In this case, it has been found that primary amines have the most pronounced effect on the reaction. For example,... 

Nitrogen substituted porphyrazines were the second type of heteroatom-deriva-tized pz macrocycle reported and were prepared from the readily derivatized diami-nomalconitrilc (DAMN) (7). Octakis(dimethylamino)porphyrazines are extremely electron-rich systems and have been used to prepare charge-transfer complexes with Cgo, as well as to peripherally chelate metals or convert to crown appended systems (38, 39). The unsymmetrical dimethylaminoporphyrazine analogues have also been reported (29), as well as the first example of the desymmetrized seco-pz from the dimethylaminoporphyrazine (8, 40). The nitrogen substituted porphyrazines are discussed in Section V. 

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