A challenging step in the preparation of tetrahydrocannabinol
analogs
is an acid-catalyzed intramolecular cyclization of the cannabidiol
precursor. This step typically affords a mixture of products, which
requires extensive purification to obtain any pure products. We report
the development of two continuous-flow protocols for the preparation
of (−)-trans-Δ9-tetrahydrocannabinol
and (−)-trans-Δ8-tetrahydrocannabinol.