Regioselective One‐Pot Synthesis of Triptycenes via Triple‐Cycloadditions of Arynes to Ynolates

Abstract

We developed the novel one-pot synthetic method of substituted triptycenes by the reaction of ynolates and arynes. This four-step process involves three cycloadditions and electrocyclic ring opening of the strained Dewar anthracene. Each of the three related but structurally distinct classes of nucleophiles (ynolate,enolate,and anthracenolate) reacts with o-benzyne in the same predictable manner controlled by chelation and negative hyperconjugation. The resulting functionalized C 3-symmetrical triptycenes hold promise in the design of functional materials.

3-Trifluoromethylbenzyne: Precise Orientation in Cycloaddition Reaction Enabled Regioselective Synthesis of Trifluoromethylated Triptycenes

“…In a similar way, as we have shown earlier, 8a 12 the Diels–Alder reaction of anthranoxide and benzynes is noticeably asynchronous: nucleophilic addition of anthranoxide to the benzyne precedes the formation of the second C–C bond. Therefore, polarization of the trifluoromethylbenzyne triple bond would also play a significant role in this step.…”

“…The high regioselectivity observed in both the ynolate and anthrone methods could be attributed to the polarization of the in-plane π-orbital due to the electronegative nature of the CF 3 group. As is the case with methoxybenzyne, 8a the addition of both lithium ynolate 1 and benzocyclobutenone enolate 3 to trifluoromethylbenzyne will selectively occur at the C1 position. These asynchronous cycloadditions start as nucleophilic additions to the alkyne moiety.…”

“…Therefore, polarization of the trifluoromethylbenzyne triple bond would also play a significant role in this step. Additionally, because Li–O interaction was highly important to form precomplexes in the case of methoxybenzyne, 8a one can suggest that Li–F noncovalent interactions 20 may also contribute to the regioselectivity of these trifluoromethylbenzyne cycloadditions.…”

“…Recently, we have developed a novel synthetic approach to triptycenes via triple cycloaddition of ynolates 7 1 with benzynes 2 (Scheme 1, a ). 8 It is noteworthy that using 3-methoxybenzyne 8a and 3-silylbenzynes 8b as reactants results in regioselective formation of functionalized triptycenes with substituents at the 1,8,13-positions. 9 In the case of 3-methoxybenzyne ( 2a ), this high selectivity is derived from the presence of the methoxy group.…”

Synthesis of Phosphachromones by Cyclized Coupling of Ethyl Hydrogen (Phenylethynyl)phosphonate with Arynes

“…11a,f,12 Recently, our group reported the synthesis of ortho-sulfurative arylphosphanes from arynes, P(O)H, and elemental sulfur via a one-pot strategy. 13 Given these favorable attributes, we hypothesized that using alkynylphosphine oxides with arynes might furnish the corresponding phosphacycle products under transition-metalfree conditions (Figure 1B, strategy d).…”