Calix[4]arenes Substituted on the Narrow Rim with Malononitrile and Cobalt Bis(dicarbollide) Anion

Abstract

Nitrile groups are suitable precursors for amino functions to which various other groups can be attached. Thus, the reaction of the 1,3-bis(3-bromopropyl ether) or 1,3-bis(4-bromobutyl ether) of tert-butylcalix[4]arene with methylmalononitrile has been studied in order to attach four nitrile groups to the narrow rim. Bimacrocyclic dinitriles were formed in 70% yield with malononitrile, and tetranitriles in 85% yield with methylmalononitrile. Subsequent alkylation of the tetranitriles with cobalt dioxane-bis(dicarbollide) gave dianionic calix[4]arenes, isolated as the cesium salts in 68% and 89% yield. Two compounds were characterized by single crystal X-ray analysis.

Key words

calixarenes - boron - clusters - alkylation - nitriles

References

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9

A reaction of 5b with malononitrile in THF at -78 ˚C using LDA as base led to a complicated mixture from which the expected tetranitrile could be isolated in 12% yield.

10

Crystal data for 6a: C₅₃H₆₆N₂O₄×2MeCN, M = 877.19, monoclinic, a = 13.8422(4) Å, b = 18.3275(6) Å, c = 42.7189(11) Å, β = 97.642(2)˚, V = 10741.2(5) Å^³, T = 173(2) K, space group P2₁/c, Z = 8, µ(Mo Kα) = 0.068 mm^-¹, 95208 reflections measured, 19962 unique reflections which were used in all calculations. The final wR(F ^²)[I > 2σ(I)] was 0.2685. Crystallographic data in CIF format have been deposited with the Cambridge Crystallographic Data Centre, reference no. CCDC 642222, and can be obtained on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: [phone]; E-mail: [e-mail].

11

Crystal data for 7a: C₅₈H₇₂N₄O₄, M = 889.20, triclinic, a = 10.3770(4) Å, b = 13.3048(6) Å, c = 20.2318(9) Å, α = 92.798(3)˚, β = 90.151(3)˚, γ = 93.368(3)˚, V = 2785.1 (2) Å^³, T = 173 (2) K, space group P 1, Z = 2, µ(Mo Kα) = 0.066 mm^-¹, 77572 reflections measured, 11334 unique reflections which were used in all calculations. The final wR(F ^²)[I > 2σ(I)] was 0.1509. Crystallographic data in CIF format have been deposited with the Cambridge Crystallographic Data Centre, reference no. CCDC 642221.