The photochemical and oxidative cyclodehydrogenation reactions of tetraphenylpyrroles act in a complementary fashion for the cyclisation of N-ethyl and N-benzyl derivatives. In the case of the former, a doubly cyclised product was isolated from cyclisation with solid FeCl, while the latter gives a rearranged 3H-pyrrole upon irradiation.

The reaction of N,N′-dimethylene-2,2′-biimidazole (L) with various copper salts gives eight complexes that were characterized structurally in the solid state. This showed that the ligand can effectively bridge two copper atoms in close proximity similarly to the well-known bridging carboxylate motif. In reaction with copper(II), this gives a dimer (acetate, 1) or quadruple helicate (perchlorate, 2). Extention to copper(I) with a coordinating counterion gives a one-dimensional polymer (iodide, 3), while reaction with noncoordinating counterion gives M2L3 triple helicate motifs. These helicates were found to form chiral solvate-containing pockets surrounding benzene when combined with a three-fold symmetric anion (BF4 –, ClO4 – and NO3 –, 4, 5, and 6, respectively) or an achiral complex with only acetonitrile (ClO4 –, 7). While the pocket could accommodate fluorobenzene (BF4 –, 8), more highly substituted benzenes do not allow its formation.

Photochemical oxidative cyclodehydrogenation reactions are a versatile class of aromatic ring‐forming reactions. They are tolerant to functional group substitution and heteroatom inclusion, so can be used to form a diverse range of extended polyaromatic systems by fusing existing ring substituents. However, despite their undoubted synthetic utility, there are no existing models—computational or heuristic—that predict the outcome of photocyclisation reactions across all possible classes of reactants. This can be traced back to the fact that “negative” results are rarely published in the synthetic literature and the lack of a general conceptual framework for understanding how photoexcitation affects reactivity. In this work, we address both of these issues. We present experimental data for a series of aromatically substituted pyrroles and indoles, and show that quantifying induced atomic forces upon photoexcitation provides a powerful predictive model for determining whether a given reactant will photoplanarise and hence proceed to photocyclised product under appropriate reaction conditions. The propensity of a molecule to photoplanarise is related to localised changes in charge distribution around the putative forming ring upon photoexcitation. This is promoted by asymmetry in molecular structures and/or charge distributions, inclusion of heteroatoms and ethylene bridging and well‐separated or isolated photocyclisation sites.

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