Cyclotetrabenzoin: Facile Synthesis of a Shape-Persistent Molecular Square and Its Assembly into Hydrogen-Bonded Nanotubes

Cyanide‐catalyzed benzoin condensation of terephthaldehyde produces a cyclic tetramer, which we propose to name cyclotetrabenzoin. Cyclotetrabenzoin is a square‐shaped macrocycle ornamented with four α‐hydroxyketone functionalities pointing away from the central cavity, the dimensions of which are 6.9×6.9 Å. In the solid state, these functional groups extensively hydrogen bond, resulting in a microporous three‐dimensional organic framework with one‐dimensional nanotube channels. This material exhibits permanent—albeit low‐porosity, with a Langmuir surface area of 52 m2 g−1. Cyclotetrabenzoin’s easy and inexpensive synthesis and purification may inspire the creation of other shape‐persistent macrocycles and porous molecular crystals by benzoin condensation. Organized chemistry! Cyclotetrabenzoin is easily synthesized by benzoin condensation of terephthaldehyde, and organizes into an extensively hydrogen‐bonded microporous structure (see figure), which resembles Barcelona viewed from the air!