Acid catalysed condensation of resorcinol and pyrogallol with aromatic aldehydes using a microfluidic vortex fluidic device (VFD) under continuous flow conditions results in the selective formation of resorcin[4]arenes and pyrogallol[4]arenes as predominantly their C(4v) isomers. Notably C(2v) isomers and C(2h) isomers can be also prepared with the latter being converted to the C(4v) isomer when the VFD operates in confined mode.