Arynes are among the most active organic intermediates and have found numerous applications in expeditious preparation of substituted arenes. In the past 20 years, chemists have witnessed a resurgence in aryne chemistry, which is mainly attributed by the extensive utilization of Kobayashi's method, a fluoride-induced removal of the TMS group with concomitant departure of its ortho OTf group on o-silylaryl triflates. Nowadays, o-silylaryl triflates are the most frequently employed aryne precursors. This review provides an overview of the history of Kobayashi's method, its methodological achievements, and its applications in the synthesis of natural products, bioactive molecules, and polycyclic aromatic hydrocarbons.
Although
benzyne has been well-known to serve as a synthon that
can conveniently prepare various 1,2-difunctionalized benzenes, the
sites other than its formal triple bond remain silent in typical benzyne
transformations. An unprecedented aryne 1,2,3,5-tetrasubstitution
was realized from 3-silylbenzyne and aryl allyl sulfoxide, the mechanistic
pathway of which includes a regioselective aryne insertion into the
SO bond, a [3,6]-sigmatropic rearrangement, and a thermal
aromatic 1,3-silyl migration cascade.
Both
1,2,4-trisubstitution and dearomative 1,2,4-trifunctionalization
of benzyne have been accomplished from sulfoxides bearing a penta-2,4-dien-1-yl
moiety. These cascade transformations proceed through a benzyne insertion
into the SO bond and an uncommon regiospecific anionic [4,5]-sigmatropic
rearrangement, furnishing a C–O, C–S, and C–C
bond on the C1-, C2-, and C4-position of a benzene ring, respectively.
This study showcases new cascade benzyne reaction modes involving
both distal C–H bond functionalization and dearomatization.
The stannum-ene reactions of both benzyne and cyclohexyne were realized, which is particularly suitable for cyclohexyne with a broad substrate scope and excellent chemoselectivity. Our DFT calculations via distortion/interaction analysis revealed that both stannum-and hydrogen-ene reactions with cyclohexyne have later transition states due to their higher distortion energies in the transition states than those in benzyne reactions, which lead to enhanced Pauli repulsion as the decisive factor in the interaction energy accompanied with enlarged energy gap between two types of ene reactions. Therefore, excellent chemoselectivity was disclosed in the cyclohexyne-ene reaction.
The stannum-ene reactions of both benzyne and cyclohexyne were realized, which is particularly suitable for cyclohexyne with a broad substrate scope and excellent chemoselectivity. Our DFT calculations via distortion/interaction analysis revealed that both stannum-and hydrogen-ene reactions with cyclohexyne have later transition states due to their higher distortion energies in the transition states than those in benzyne reactions, which lead to enhanced Pauli repulsion as the decisive factor in the interaction energy accompanied with enlarged energy gap between two types of ene reactions. Therefore, excellent chemoselectivity was disclosed in the cyclohexyne-ene reaction.
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