FUNCTIONALIZATION OF P-TERT-BUTYLCALIX[6]ARENE BY ALKYLATION WITH 2-(CHLOROMETHYL)PYRIDINE HYDROCHLORIDE

A study of the base-catalyzed alkylation of p-tert-butylcalix[6]arene (1) with 2-(chloromethyl)-pyridine in DMF has led to the isolation and identification of 10 of the 12 possible pyridinyl homologues of 1. The identity of the base applied and molar ratios between the reactants play an important role in determining the product distribution. Regioselective 1,2,4,5-tetra-O-alkylation is realized with NaH as the base, while the use of BaO/Ba(OH)2 affords in high yield 1,4-diether 5, which is isolated as a barium complex. The reactions with limiting amounts of alkylating agent and K2CO3 produce invariably complex mixtures with 1,2,3-triether 6 as the major product. The structure of the products has been established by elemental analysis, FAB (+) mass spectral measurements, and NMR techniques. [(2-Pyridylmethyl)oxy]calix[6]arene homologues show in most cases broadened H-1-NMR spectra at rt, which sharpen at higher temperatures, allowing for a distinction between the various regioisomers. FAB (+) mass spectra and some NMR features arising from the substitution patterns at the lower rim are discussed.