Functionalization at the lower rim phenolic OH groups

The functionalization of calixarenes at the lower rim can be either partial (selective) or complete and can be carried out with a large variety of reagents.4 

The partial and selective functionalization allows the design and synthesis of a large variety of receptors for ions and neutral molecules bearing mixed functionalities. Especially in calix[4]arenes, the significant differences in the pK.d values of the phenolic OH groups allow their stepwise deprotonation and hence their selective functionalization. 

Caution Carry out all procedures in a well-ventilated hood, and wear disposable vinyl and latex gloves and chemical-resistant safety goggles. Alkylating reagents are highly toxic. 

The following procedure is representative of the di-alkylation of several para-substituted calix[4]arenes. 

Support the flask on a stirrer with a clamp and assemble the condenser on the main neck. Let a small nitrogen flux pass through the glassware until it returns to room temperature. Then insert a calcium chloride drying tube on top of the condenser.0 

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