Nucleophilic addition nitrogen-containing nucleophiles

In this article, special attention has been paid to cyclopropanations, Diels-Alder reactions, and nucleophilic substitutions, for which numerous works have been devoted to the use of Ar,N-containing ligands. Other classical reactions allowing the formation of a new C - C bond have been omitted here (e.g., Michael-type additions or aldol reactions) where they have also been, to a lesser extent, efficiently performed using nitrogen-containing ligands. 

Addition of Ketene Acetals and Enoles In recent years, much attention has been given to the synthesis of optically active nitrogen-containing compounds, with the key step being the highly stereoselective nucleophilic addition of ketene silyl acetals to nitrones (Scheme 2.174). Similar to nitrone cyanations, in ketene silyl acetal reactions one observes an accelerating effect with thiourea derivatives (633). 

Acetylenecarboxylic esters, reactions with nitrogen-containing heterocycles, 23, 263 Acetylenic derivatives of pyrazoles, synthesis and properties of, 82, 1 Acetylenic esters, synthesis of heterocycles through nucleophilic additions to, 19,297 Acid-catalyzed polymerization of pyrroles and indoles, 2, 287... 

Tandem radical additions have also been utilized for the synthesis of nitrogen containing heterocycles. These reactions have the same requirements as those discussed for the oxygen heterocycles. The reductive addition of phenylsulfanyl radicals to the unsaturated amide 153 has been investigated [95JCS(P1)19], The nucleophilic radical adds selectively to the enamide followed by 5-exo-cyclization to give 154 in excellent yield with high trans selectivity. 

Ammonia and other nitrogen-containing nucleophiles react readily with internally fluorinatcd alkenes (e. g.. 28) to form products via addition-elimination sequences. The product ratio (e. g., of 29 and 30) depends strongly on the reaction conditions. 

Tripathi VK, Venkataramani PS, Mehta G (1979) Addition of nitrogen-containing, oxygen-containing, and sulfur-containing nucleophiles to aryl ethynyl ketones. J Chem Soc Perkin Trans 1 36-41... 

The nucleophilic addition reactions of enolates to imines and related compounds (the so-called Mannich-type reactions, equation 39) are important tools in organic synthesis and a variety of electrophiles have been used to obtain the resulting nitrogen-containing... 

The donor properties of nitrogen-containing systems make these nucleophiles excellent participants in substitution reactions of oxiranes (Equation 16). The major issue for additions to unsymmetrical epoxides is one of regioselec-tivity. Both steric and electronic effects within the electrophile and the nucleophile can play a significant role in these... 

The reaction of selenoamides and selenourea with aldehydes and ketones has been known to take place via the nucleophilic attack of the selenium atom and end up in the formation of a variety of selenium- and nitrogen-containing heterocycles [99]. For example, selenourea was treated with j0-keto ester in the presence of KOH to give selenouracil (Eq. 27) [100], and its biological activity has been tested [100b]. Very recently, Lewis acid mediated addition of primary selenoamides to a, -unsaturated ketones has been reported to give 1,3-selena-zines (Eq. 28) [99 f]. 

A number of reactions of nitrogen-containing nucleophiles with aldehydes and ketones involve addition of the nitrogen to the carbon of the carbonyl group, followed by elimination of water to produce a double bond. Common examples are reactions of primary amines to produce substituted imines, reactions of secondary amines to produce enamines, reactions of hydrazine or substituted hydrazines to produce hydrazones, reactions of semicarbazides to give semicarbazones, and reactions of hydroxylamine to produce oximes. Usually these reactions are run with an acid catalyst. 

The reaction of 2potassium amide in liquid ammonia to give 2-cyanoimidazole, imidazole, and 2-aminopyridine has been investigated (911). It has been found that 2-chloropyrazine containing an excess of in position 1, on treatment with potassium amide in liquid ammonia at — 65° yields 2-aminopyrazine in which the exocyclic nitrogen contains all the excess and an addition-nucleophilic-ring opening-ring closure (ANRORC) mechanism was proposed (822). The mechanism of the conversions into imidazole (823) and... 

Cyclopropyllithium may engage itself in various types of reactions depending on the properties of the aromatic compound. When fluorobenzene is the aromatic substrate, benzyne formation followed by hydride transfer is believed to take place, but if the aromatic compound is a diazine or a substituted or annulated pyridine, the first step is nucleophilic addition of cyclopropyllithium to the nitrogen-containing ring of the aromatic nucleus. The predominance... 

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