关键词:
vinylidene
alkyne
rearrangement
ruthenium
molecular activation
C-C bond activation
cyclization
indole
naphthalene
摘要:
Formation of monosubstituted vinylidenes from terminal alkynes at metal complexes as well as its mechanisms has been well studied, and this process is now recognized as a powerful and reliable method for the activation of terminal alkynes in organic chemistry. In contrast, the formation of disubstituted vinylidenes from carbon-based internal alkynes via 1,2-migration of a carbon substituent remained elusive. In this article, we describe our studies on the vinylidene rearrangement of common internal alkynes at group 8 metal complexes and its application to organic synthesis. Anionic and cationic group 8 metal complexes can affect the vinylidene rearrangement of carbon-substituted internal alkynes via the 1,2-migration of aryl and alkyl groups. The migratory aptitude of aryl groups was investigated experimentally and theoretically, and the results reveal that, unlike the general nucleophilic rearrangements, the less-electron donating aryl group preferentially migrates as the nucleophile in the vinylidene rearrangement. This vinylidene rearrangement using a cationic ruthenium complex was successfully applied for catalytic transformations of 2-alkynylaniline, 3-amino-4-alkynylcoumarin, and 2-alkynylstyrene derivatives that lead to 3-substituted indole, 1-arylpyrrolocoumarin, and 1-disubstituted naphthalene derivatives, respectively.