Selective Functionalization of a Single Methylene Bridge of a Calix[6]arene

Abstract

The monohydroxycalix[6]arene derivative 4a was prepared via photochemical bromination of hexamethoxycalix[6]arene 3a in aq THF. Monohydroxycalix[6]arene 4a and its chloro derivative 5 are useful synthetic intermediates for the preparation of structurally diverse calix[6]arenes functionalized at a single methylene bridge.

Preparation of Calix[8]arene Derivatives Functionalized at a Single Methylene Bridge

“…The same method was recently applied to the preparation of monofunctionalized calix [6]arene derivatives. [7] Key intermediates in this route were the monohydroxy calix [6]arene derivative 3 (obtained by photochemical bromination of hexamethoxycalix [6]arene 1b in aqueous THF), and its chloro derivative 4 (Scheme 1). Monofunctionalized calix [6]arenes incorporating alkoxy, acetylacetonyl, or aryl groups were prepared through the reaction of 3 or 4 with nucleophiles under S N 1 conditions.…”

“…Monofunctionalized calix [6]arenes incorporating alkoxy, acetylacetonyl, or aryl groups were prepared through the reaction of 3 or 4 with nucleophiles under S N 1 conditions. [7] Scheme 1. Preparation of the large-ring monohydroxy and monochlorocalixarenes.…”

“…[8] Taking advantage of the synthetic availability of the monohydroxycalix [8]arene 5, [7] herein, we describe the preparation of calix [8]arenes derivatives possessing a single, monofunctionalized methylene bridge.…”

“…Calix [8]arenes derivatives possessing two bridges substituted with alkyl groups or a single bridge substituted with a p-nitrophenyl group have been obtained in low yield in a [3+2] fragment condensation reaction of a linear trimer with bis(bromomethylated) alkanediyl diphenols. [8] Taking advantage of the synthetic availability of the monohydroxycalix [8]arene 5, [7] herein, we describe the preparation of calix [8]arenes derivatives possessing a single, monofunctionalized methylene bridge.…”

Calix[6]arene Derivatives with Differently Modified Bridges

“…[7] Using a different approach, monochlorocalix[n]arenes 3b and 3c (Scheme 1) were prepared via photochemical reaction of 1c and 1d with NBS in a THF/water/CaCO 3 mixture, followed by treatment of the monohydroxycalix[n]arene product with SOCl 2 . [8] Recently, a calix[6]arene derivative with a pair of opposite chloromethylene bridges was prepared via a lithiation/oxygenation of 1c, affording a derivative with a pair of opposite bridges hydroxylated, followed by reaction of the product with SOCl 2 /Et 3 N. [9] Bromination of the methylene bridges of a Boc-protected calix[6]arene derivative [10] with excess NBS proceeded only up to the tetrabrominated stage. [11] Scheme 1.[a]…”