The synthesis and characterisation of the reactive tetrakis(0,O-phosphorus)-bridged calix[4]resorcinols 3 and 4 is described. Because of its poor solubility in common organic solvents, a solid-state NMR investigation of 3 (lH, 13C, 'lP) was conducted. Reaction of 3 with MeMgI, Me,SiNMe2, and HNMe2 furnished the 03h3P-substituted cavitands 5 and 6. Oxidative addition reactions of 6 with the (H2N)2C(=O)/H202(1: 1) adduct, tetrachloro-o-benzoquinone (TOB), and hexafluoroacetone (HFA) led to the n4h5P derivative 7, and to the n5h5P derivatives 8 and 9. An X-ray crystal-structure determination of the tetrakis(0,O-phosphorus)-bridged calix[4]resorcinol 4 has been conducted. The framework displays the cone conformation; the chlorine atoms are directed inwards.

Unlike C‐undecylcalix[4]resorcinarene, C‐methylcalix[4]resorcinarene 1 reacted with chlorodifluorophosphine in the absence of an auxiliary base to give the unstable octakis(difluorophosphite)‐substituted derivative 2. The existence of two conformational isomers of 2 in solution was observed by 19F and 31P NMR spectroscopy. Attempts to react the octakis(trimethylsilyl)calix[4]resorcinarene 3 and its tetrabromo derivative 4 with phosphorus trichloride and chlorodifluorophosphine were unsuccessful. The ethoxy‐tethered C‐methyl‐octakis(trimeth‐ylsilyl)calix[4]resorcinarene 5 was allowed to react with 2‐chloro‐1,3,5‐trimethyl‐1,3,5‐triaza‐2σ3λ3‐phosphorin‐4,6‐dione and chlorodifluorophosphine. By substitution of all trimethylsilyl groups, the octakis(phosphorus(III))‐substituted compounds 6 and 7 were formed. As for 2, dynamic behavior in solution was observed for 6 and 7, arising from the equilibrium between different conformational isomers. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:553–558, 1998

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The octakis(trimethylsiloxy)calix[4]resorcinarenes, 3 and 4, were synthesized by reaction of 1 and its tetrabromo derivative 2 with hexamethyldisilazane, and were found to exhibit dynamic behaviour in solution. Temperature-dependent NMR investigations confirmed the presence of at least two conformational isomers of 3 in solution. The conformation of 3 in the solid state was determined by an X-ray crystal structure analysis; the calixarene displays a boat conformation. The introduction of the ethoxy group as a spacer into the molecule of 1 was effected via its reaction with ethyl bromoacetate and subsequent reduction with lithium aluminium hydride forming the ethoxy-tethered C-methylcalix[4]resorcinarene 6 in an impure state. Reaction of crude 6 with hexamethyldisilazane furnished the ethoxy-tethered octakis( trimethylsiloxy)calix[4]resorcinarene 7; its hydrolysis led to pure 6.