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 -symmetrical triptycenes hold promise in the design of functional materials.

Enantioselective Synthesis of Distorted π‐Extended Chiral Triptycenes Consisting of Three Distinct Aromatic Rings by Rhodium‐Catalyzed [2+2+2] Cycloaddition

“…In 1956, Wittig and Ludwig reported the practical one‐step synthesis of triptycene by the Diels–Alder reaction of anthracene with benzyne . After this report, a number of efficient methods (e.g., the Friedel–Crafts reaction, the [2+2+2] cycloaddition, and the [2+2] cycloaddition approaches) have been reported for the synthesis of structurally diverse triptycene derivatives.…”

Synthesis of Distorted 1,8,13‐Trisilyl‐9‐hydroxytriptycenes by Triple Cycloaddition of Ynolates to 3‐Silylbenzynes

“…Recently, we developed a sequential triple addition reaction of ynolates to arynes to form triptycenes, where three arynes are formally condensed to an ynolate, along with cleavage of the triple bond in one pot (Scheme (a)) . When substituted arynes are used as a substrate, functionalized and/or pre‐functionalized triptycenes can be prepared.…”

“…This synthetic limitation is ac riticald rawback for syntheses of functionalized designed triptycenes.Recently,w ed eveloped as equential triple addition reaction of ynolates [9] to arynes to form triptycenes, where three arynes are formally condensed to an ynolate, alongw ith cleavageo f the triple bond in one pot (Scheme 1(a)). [10] When substituted arynes are used as as ubstrate, functionalized and/or pre-functionalized triptycenes can be prepared.I napreviousr eport, we also describedt he selective synthesis of 1,8,13-trimethoxytriptycenes (X = OMe) by using 3-methoxybenzyne, highlighting the secondary orbital interactions as am ajor controlling factor of the selectivity in addition to the inductive effect [11] and distortion model. [12] It shouldb en oted that the 1-, 8-, and 13-positionsa re located on the same plane (blue trianglei n Scheme 1(b)) and the substituents at thesep ositions are oriented vertically from the plane.A lthough this uniques tructure could be used as ap latform for functionalized triptycenes, [13] efficient synthetic methods for this type of triptycene have rarely been reported.T his triple addition methodc an be applied to the short-step synthesis of functionalized triptycenes.Silylarenes are frequently used as powerful synthetic tools in synthetic organic chemistry because their silyl groups can be converted into other substituents.I fs ilylarynes could be applied to the triple addition, the resulting triptycenes would be usefula sp recursors for functionalized triptycenes.H owever, these silylarynesh ave only been used in af ew organics yntheses.…”

Benzocyclobutadienes: An Unusual Mode of Access Reveals Unusual Modes of Reactivity

“…However, reports of such transformations are extremely rare. [3,4] This is surprising because the reaction of a benzyne with an alkyne is computed to be significantly exergonic (cf. 58.5 kcal•mol −1 for 9 to 10 , Figure S1 in the SI) and to proceed with a low activation energy.…”

“…[3] In the only other example of this type of process to our knowledge, Shindo and Alabugin recently reported the reaction of various benzynes with electron-rich ynolates 4 to give triptycenes 6 , which they proposed to arise via initial formation of formal [2+2] adducts 5 (Figure 1b). [4] …”