Expanded Cyclotetrabenzoins

Cyclobenzoins are stable and shape-persistent macrocycles which offer promise as components of optoelectronic and porous materials. We report three new cyclotetrabenzoins, derived from biphenyl, naphthalene, and tolane skeletons. Their synthesis relied on the N-heterocyclic carbene-catalyzed benzoin condensation. Isolated as their acetic esters, these compounds are characterized by structures similar in shape, but larger in size than the parent cyclotetrabenzoin. Alkyne groups of the tolane-based cyclotetrabenzoin were post-synthetically functionalized with Co2(CO)6 moieties under mild reaction conditions.