Heterocyclic intramolecular nucleophilic attack

The intramolecular nucleophilic attack of a nitrogen atom on an allylpalladium complex was also used to construct a five and a six membered heterocycle in the same step. TV-substituted 2-iodobenzamides bearing an allene function in the appropriate distance from the iodine underwent cyclization through the carbopalladation of the allene moiety by the arylpalladium complex, formed in the first step of the catalytic cycle. The intermediate allylpalladium complex, part of a nine membered ring, cyclized readily to give the pyrroloisoquinolone derivative in excellent yield (4.23.). The nature of the added ligand and the solvent both had a marked influence on the efficiency of the transformation.26... 

Arenetellurolates have been used as starting materials for the preparation of heterocyclic compounds. Intramolecular nucleophilic attack by tellurium on the acetylenic carbon in 2-ethynyl-2-propenetellurolate yielded a 2,3-dihydrotellurophene derivative3 (p. 408). 

In another example of heterocyclic ring synthesis, pyridinium salts 816 require only Et3N for deprotonation, the resulting ylides 817 add to esters of 2-bromo-2-alkenecarboxylic acids or analogous benzonitriles to give intermediate betaines 818 which, via intramolecular nucleophilic attack, give indolizines 819 (Scheme 174) <1999JOC7618>. 

Classical reactions involving nucleophiles such as saponification ("OH as the nucleophile), aminolysis (with amines also ammonia in ammonolysis reactions), transesterification (alkoxides, "OR) and others (hydrazinolysis, hydroxamic acid synthesis, etc.) have been adapted to solid phane and used to obtain, for instance, carboxylic acids, amides and esters. Internal or intramolecular nucleophilic attack has been employed to obtain cyclic products such as lactones, lactams (including cyclic peptides) and a great variety of heterocycles (hydantoins, diketopiperazines, benzodiazepinones, etc.). 

The reactivity of allenylpalladium species, derived from oxidative addition of propargyl alcohol derivatives to palladium (0), has attracted considerable attention in organic synthesis.283 Recently, the intramolecular reaction of the propargylic derivatives 665 with an oxygen and nitrogen nucleophile has been widely utilized for the synthesis of heterocyclic compounds. The key step of formation of a heterocyclic ring is intramolecular nucleophilic attack of a... 

The majority of the reactions of this type that lead to the heterocyclic systems discussed in this chapter involve formation of a bond between a carbon and a heteroatom. Intramolecular nucleophilic attack by the oxime oxygen on the dithiocarbonate thiocarbonyl group in (103) gives the... 

Kang et al. also demonstrated that in the presence of CO (20 atm), the car-bonylative coupling cyclization of 2,3-, 4,5-, or 5,6-allenylamines with Arl can be realized to afford aroyl-substituted N-containing heterocycles 43 and 44 (Scheme 24) [17]. The reaction proceeded via aroylpalladation of the allene moiety leading to a 71-allyl palladium intermediate, which underwent an intramolecular nucleophilic attack to form the product (pathway 1, Scheme 1). 

Intramolecular nucleophilic attack onto the carbon centres of nitriles constitutes a common strategy employed in the synthesis of heterocyclic amines. However, a recent preparation of 5 -amino-m-terphenyls from arylidene and 1-arylethylidene-malononitriles has demonstrated that such reactions can be applied to the synthesis of carbocyclic amines (Scheme 3). 

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