Rapid Access to Dibenzohelicenes and their Functionalized Derivatives
作者:Andrej Jančařík、Jiří Rybáček、Kevin Cocq、Jana Vacek Chocholoušová、Jaroslav Vacek、Radek Pohl、Lucie Bednárová、Pavel Fiedler、Ivana Císařová、Irena G. Stará、Ivo Starý
DOI:10.1002/anie.201301739
日期:2013.9.16
Spiraling up: Easy access to dibenzo[5]‐, dibenzo[6]‐, and dibenzo[7]helicenes (see picture) as well as their functionalizedderivatives includes Sonogashira and Suzuki–Miyaura couplings, desilylation, and [2+2+2] alkyne cycloisomerization. The simplicity of this non‐photochemical approach combined with the potential for helicity control favors dibenzohelicenes over the parent helicenes for practical
reaction showed compatibility with both electron‐poor and electron‐rich substrates, thus allowing the synthesis of pyridine‐ and thiophene‐fused nanographenes. It also enabled the synthesis of sterically hindered contorted π‐conjugated molecules without causing full aromatization. A kinetic study showed that the CDHC reaction under the conditions used is a very fast process, and some reactions are completed
of 1 resolved by chiral HPLC underwent facile racemization with an activation energy of 90.6 kJ mol–1. Transannularcyclization of 1 was induced by heating to generate benzyne intermediate 8, which was intercepted by furan to give 9, and by treatment with bromine to give dibromodibenzopicene (10).
Chiral Conflict among Different Helicenes Suppresses Formation of One Enantiomorph in 2D Crystallization
作者:Johannes Seibel、Oliver Allemann、Jay S. Siegel、Karl-Heinz Ernst
DOI:10.1021/ja402012j
日期:2013.5.22
monolayer, only the (M)-pentahelicene enantiomorph is observed. This effect is explained by a preferred heterochiral interaction between the differenthelicene species, suppressing the formation of the pure (P)-pentahelicene enantiomorph. These results shine new light onto stereoselective molecular recognition mediated by van der Waals forces.
Shedding UV‐Light on Mechanochemistry: The Regioselective Solid‐State Photochemical Synthesis of Nanographenes
作者:Daniel M. Baier、Carolina Spula、Stephen Fanenstich、Sven Grätz、Lars Borchardt
DOI:10.1002/anie.202218719
日期:——
Photochemistry and mechanochemistry have been combined to synthesize nanographenes in the complete absence of bulk solvents. The concept is showcased with two reactions—the Mallory reaction and the cyclodehydrochlorination, both applicable to the intramolecular formation of C−C bonds. Moreover, the approach can even form these bonds regioselectively in larger systems—something not possible before in