Electrophilic Reactions of Carbenoids. Synthesis of Fused Heterocyclic Systems via Intramolecular Nucleophilic Substitution of Carbenoids

Article abstract of DOI:10.1021/jo00122a046

Intramolecular nucleophilic substitution of carbenoids with oxygen, nitrogen, and sulfur nucleophiles leading to the synthesis of fused heterocyclic compounds has been studied.For the purpose of this investigation styryl type gem-dihalides 4, 8, 18, 20, 28 containing a nucleophilic substituent in the ortho position of the aromatic ring have been synthesized.Carbenoids have been generated in those systems by the halogen - metal exchange reaction and shown to readily undergo intramolecular nucleophilic substitution by the properly located nucleophilic group (OH, SH, or NH2).As a result a new synthetic route to benzofurans, thianaphthenes, and indoles has been established based on nucleophilic substitution of vinyl halides by an ortho substituent.The dramatic increase of reactivity of vinyl halides upon introduction of lithium has been explained as being due to metal-assisted ionization.