Carbon-nitrogen bonds intramolecular additions

Reactions of Alkynyl Amines In 2004, Shimada et al. reported that platinum-catalyzed intramolecular carbon-nitrogen bond addition reaction, called... 

Epielwesine. Intramolecular addition of vinylsilanes, catalysed by acid to an appropriately sited carbon-nitrogen double bond, which featured as the key step for the efficient construction of a variety of heterocycles, [86] was successfully applied to the synthesis of ( )-epielwesine (335) (Scheme 49) by Overman et al. [87]. The requisite starting material, the... 

The nitrile group in cyanopyridine can participate in intramolecular reactions. The presence in chalcone 118 of an ortho-hydroxyl substituent can lead to its addition to a carbon-nitrogen triple bond, with the formation of the 2/7-pyran-2-iminic moiety (compound 119) [126, 127] (Scheme 3.36). 

Intramolecular addition of amine N-H bonds to carbon-carbon multiple bonds would afford nitrogen heterocycles. To realize catalytic cyclization of a,co-aminoalkenes or aminoalkynes, various catalytic systems have been developed especially with early transition metals such as titanium, zirconium, lanthanide metals, and actinide metals [ 12], Late-transition-metal catalysis based on Ni, Pd, and Rh has also proved to be efficient [ 12], Recently, the ruthenium-catalyzed intramolecular hydroamination of aminoalkynes 15 was reported to afford 5-7-membered ring products 16 in various yields (Eq. 6) [13]. Among... 

Other reactions involving the cleavage of a carbon heteroatom bond include a promising method for the deprotection of benzyl ethers by irradiation in the presence of acceptors (Scheme 46) [240-241] and the liberation of alkyl radicals (capable of initiating a polymerization) from alkyltriarylborate salts [242-243], The PET induced decomposition of phenyldiazomethane leads to cis-stilbene the reaction however appears to involve addition of the radical cation to a neutral molecule prior to nitrogen loss [244]. The detachment of a halogen after intramolecular electron transfer from the a C-X bond to an electron-rich... 

Intramolecular hydroamination/cyclization, the addition of an N-H bond across an intramolecular carbon-carbon unsaturated bond, offers an efficient, atom economical route to nitrogen-containing heterocyclic molecules (Equation 8.37). Numerous organolanthanide complexes were found to be efficient catalysts for this transformation [124, 125]. The real active intermediates are organolanthanide amides, which are formed by the rapid protonolysis reactions of precatalysts with amine substrates. The proposed catalytic cycle of hydroamination/cyclization of aminoalkenes is presented in Figure 8.37 [124]. 

The cyclization of 4,5-hexadienamines and -amides, catalyzed by palladium salts in the presence of copper(II) chloride under a carbon monoxide atmosphere, afforded 2-(2-pyrrolidinyl)acrylates. A different mechanism is operating here, which does not involve the intramolecular addition of nitrogen nucleophile to a rt-complex, but, instead, the addition of PdX2 to a double bond, followed by SN2 or S 2 displacement in the cyclization step28. 

The most commonly used of these three bond classes is the formation of bond b . Formation of bond b typically occurs through an intramolecular alkylation of a nitrogen atom. A second highly prevalent method for the formation of the type I structure is the formation of bonds b and c from addition of a nitrogen across a carbon-carbon double bond. A final rarely used route is the formation of bonds c and e through the intramolecular addition of a carbene across and carbon-nitrogen double bond. Methods in which bond a is formed are rare in terms of simple fused-ring aziridines but several examples can be found in Section 1.02.7 in the discussion of the mitomycin family of alkaloids (Scheme 1). 

In these reactions, the nitrogen nucleophile is typically an amide, carbamate, or sulfonamide. Because of the low nucleophilicity of such nitrogen functions, no intermolecular 1,4-addition involving C—N bond formation is known. In all cases reported, the carbon-nitrogen coupling takes place in an intramolecular aminopalladation. 

Many approaches to y-lactams have been dependent on cyclization by acyl-nitrogen bond formation [22]. Cyclization involving carbon-carbon bond formation is an alternative route however, until recently, this potential methodology has received little attention. Mori and co-workers reported a palladium-catalyzed cyclization of A -allyl iodoacetamides, in which the intramolecular addition reaction of the carbon-iodine bond to an olefinic linkage is a key step [23]. 

Figure 2 In the peptide Phe-Gly-Cys-Gly (formed by Phenylalanine, Glycine, Cysteine and Glycine amino adds linked by peptidic bonds), the sulphur atom is very close to the phenyl ring. An Intramolecular addition ofthe CysS radical on the aromatic ring of Phe (marked with an arrow) leads easily to the alkylthio-substituted cyclohexadie-nyl radicals. A tom colors Cyan carbon blue nitrogen red oxygen yellow sulphur. H atoms are not shown.

This chapter deals with recent advances in efficient radical traps and also includes newly developed radical acceptors for both intramolecular and intermolecular addition. Special attention will be given to the synthetic importance of newly developed heteroatom radical traps, particularly carbon-nitrogen double bonds. 

Nucleophilic intramolecular addition of a carbon-silicon bond onto a carbon-nitrogen iminium ion is the key step of a berbine synthesis <82CC769,83H(20)417>. Thus, treatment of the isoquinolinium salt (235) with caesium fluoride in ethanol afforded (+)-xylopinine (237), presumably via the betaine (236) (Scheme 45). A silicon-directed intramolecular cyclization of a A-acyliminium ion (238) was also the key step of Speckamp s synthesis of (+)-epilupinine as shown in Scheme 46 <85JOC40I4>. 

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