SOFT CALIXARENES - STRUCTURAL ASPECTS OF CALIXARENE ALLYL ETHERS AND OF THIACALIXARENE SYNTHESIS

Syntheses and room-temperature single-crystal X-ray structure determin ations are recorded for an array of p-t-butylcalix[n] arenes, n = 4 or 6, diversely functionalized at the phenolic oxygen atoms: the 1,3-dia llyl 2,4-dimethyl ether for n = 4 (1), the hexaallyl ether for n = 6 ( 2), and the 1,3-dibenzyl 2,4-bis(dimethylthiocarbamoyl) derivative for n = 4 (3), with a view to establishing lip;and baseline conformations for subsequent metal complexation studies, and for exploring any incl usion properties. Compound (1) is monoclinic, P2(1)/c, a. 16.751(9), b 20.772(7), c 27.91(1) Angstrom, beta 99.39(4)degrees, Z = 8, conventi onal R on \F\ being 0.060 for N-o 4396 'observed' (I > 3 sigma(I)) ref lections. Compound (2) is triclinic, P (1) over bar, a 19.6312), b 14. 57(2), c 14.188(9) Angstrom, a 107.84(8), beta 93.26(7), gamma 99.48(1 0)degrees, Z = 2, R 0.067 for N-o 7315. Compound (3), as its methanol monosolvate, is triclinic, P (1) over bar, a 15.592(4), b 15.17(3), c 14.31(2) Angstrom; alpha 88.8(1), beta 64.3(1), gamma 75.7(1)degrees, Z = 2, R 0.076 for N-o 3802. The conformation of (1) is similar to tha t previously established for an analogue in which two of the t-butyl g roups were absent the conformation of (2) is that of a flattened 1,2,3 -alternate form, the asymmetric unit being a pair of half (centrosymme tric) dimers; the conformation of (3) is 1,3-alternate.