Opportunities Using Boron to Direct Reactivity in the Organic Solid State

This Account describes work by our research group that highlights opportunities to utilize organoboron molecules to direct chemical reactivity in the organic solid state. Specifically, we convey a previously unexplored use of hydrogen bonding of boronic acids and boron coordination in boronic esters to achieve [2+2]-photocycloadditions in crystalline solids. Organoboron molecules act as templates or ‘shepherds’ to organize alkenes in a suitable geometry to undergo regio- and stereoselective [2+2]-photocycloadditions in quantitative yields. We also provide a selection of publications that served as an inspiration for our strategies and offer challenges and opportunities for future developments of boron in the field of materials and solid-state chemistry. 1 Introduction 1.1 Template Strategy for [2+2]-Photocycloadditions in the Solid State 2 Boronic Acids as Templates for [2+2]-Photocycloadditions in the Solid State 2.1 Supramolecular Catalysis of [2+2]-Photocycloadditions in the Solid State Using Boronic Acids 3 Boronic Esters as Templates for [2+2]-Photocycloadditions in the Solid State 3.1 Application of Photoproducts: Separation of Thiophene from Benzene through Crystallization 3.2 Crystal Reactivity of B←N-Bonded Adducts: The Case of Styryl­thiophenes 4 Conclusions and Perspectives