Solvent-free synthesis of pillar[6]arenes

An efficient solvent-free procedure for the synthesis of pillar[6]-arenes has been developed. The procedure involves the solid-state condensation of finely milled 1,4-dialkoxybenzene and paraformaldehyde by grinding in the presence of a catalytic amount of H2SO4. The use of organic solvents for the extraction of products has also been avoided. Operational simplicity, compatibility with various 1,4-dialkoxybenzenes, non-chromatographic purification technique, high yields and mild reaction conditions are the notable advantages of this procedure. A large scale reaction demonstrated the practical applicability of this methodology.