Tri-tert-butyltrihydroxy[3.3.3]metacyclophane 13 was prepared in 6 steps from p-tert-butylanisole in 25% overall yield by using the TosMIC method, followed by Wolff-Kishner reduction and demethylation with boron tribromide. AlC13/ MeN0,-catalyzed trans-tert-butylation of 13 in benzene gave the desired metacyclophane 14 in 85% yield, along with tert-butylbenzene (15). Weak intramolecular hydrogen bonding was observed in the triols 13 and 14. -6,15,24-Tritert-butyl-9,18,2?-trihydroxy[3.3.3]MCP 13 was tri-0-alkylated with alkyl halides (RX: R = Et, Pr, and Bu) in the presence of Cs2C03 to yield partial-cone confomer 12b-d in quantitative yield. Ring inversion by oxygen-through-the-annulus rotation is allowed for triethoxy derivative 12b (coalescence temperature ca. 90 "C) but inhibited for the tripropoxy-1212 and the tributoxy derivative 12d. The reaction of the trio1 13 with ethyl bromoacetate in the presence of Cs2C03 yielded cone and partial-cone 12e, respectively. In contrast, a significant amount of cone conformer 12f resulted when NaH was used as base. Only when the template metal can hold the ester or amide group@) and the oxide group(s) on the same side of the [3.3.3]MCP is the conformation immobilized to the cone. -Titration of cone amide cone-12f with KSCN monitored by IH NMR clearly demonstrates that a 1 : 1 complex is formed which is stable on the NMR time scale, and the original C3 symmetry is retained after the complete metal cation complexation. -The stability of multimembered carbon skeletons permits the interconversion of functional groups without special regard to ring-opening side reactions as was observed for homotrioxacalix [3]arenes with ethereal linkages. For example, the introduction of nitro groups was accomplished on the upper rim by direct threefold ipso-nitration of tert-butyltrimethoxy derivative 12a.
Synthesis and Conformational Studies of Calixarene-Analogous Trihydroxy(3.3.3)metacyclophanes and Their O-Alkylated Derivatives.-The metacyclophane (III) is prepared in six steps from p-tert-butylanisole in 25% yield and de-tert-butylated to give the desired metacyclophane (IV). Weak intramolecular hydrogen bonding is observed in these triols. Tri-O-alkylation of (III) in the presence of Cs2CO3 leads to the formation of partial-cone conformer tri-O-alkyl derivatives in quantitative yield. Ring inversion by oxygen-throughthe-annulus rotation takes place for the triethoxy derivative, but is inhibited for the tripropoxy and tributoxy derivatives. -(YAMATO, T.; DOAMEKPOR, L. K.; KOIZUMI, K.; KISHI, K.; HARAGUCHI, M.; TASHIRO, M.; Liebigs Ann.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.