Electrophilic reactions nitrile trapping

Bromine-lithium exchange applied to the sulfide obtained from the reaction between 2-fluorobenzonitrile and 2-bromothiophenol promotes an intramolecular attack on the nitrile function. Hydrolysis of the resulting tricyclic lithio-imine produces thioxanthone (Scheme 209). Alternatively, the imine can be trapped with electrophiles... 

In contrast to the diverse insertion chemistry of vinylpalladium intermediates discussed in Sects. IV.3 and IV.5, the reactions of vinylpalladium complexes with electrophiles had not been reported until recently. Although a single report on the annulation of the o-mer-curio benzaldehyde with diphenylacetylene into the corresponding indenols and inde-nones catalytic in palladium and stoichiometric in copper had been communicated in 1992, the more synthetically useful protocol for the catalytic version of this type of transformation remained unknown until 1999. In this section the intermolecular carbopalladation of alkynes with aryl halides followed by the intramolecular trapping of the formed vinylpalladium species with ketones, aldehydes, and nitriles will be discussed. 

The copper-catalyzed cascade annulation of nitriles, diaryliodonium salts, and alkynes was recently described by Chen and coworkers. N-Arylation of the nitrile resulted in an V-arylnitrilium intermediate, which was trapped by the aUcyne and subsequently underwent electrophilic annulation to yield substituted quinolines (Scheme 6d) [107]. The concept was later varied to reach polycyclic quinolines, quinazolines, quinazolinimine, and acridine scaffolds [108—110], A similar cascade reaction delivered iminobenzoxazines by N-aiylation of ort/io-cyanoanilides followed by C-O cyclization [111], and the reactimi of nitriles with [1,1-biphenyl]-derived iodonium salts resulted in phenanthiidines [112]. The corresponding C-arylation cascade reactions are discussed in Sect. 4.3. 

In Chap. 2, the author disclosed zirconocene-mediated cyclization of bis(alky-nyl)silanes, nitriles, and unsaturated compounds. The reactive intermediates involving two or three molecules of nitriles were isolated and characterized. Thus, the author expects to further isolate the one molecule of nitrile involved intermediate and demonstrates the reaction mechanism toward the formation of Zr-/Si-containing three-ring fused intermediates (Scheme 3.1). The author tried to use only one equivalents of nitrile, lower the reaction temperature, and quench the reaction mixture generated in situ or trap with electrophiles. However, all these attempts failed, and the isolation and characterization of one-nitrile-involved intermediates... 

---