Isomerism is a fundamental chemical concept, reflecting the fact that the arrangement of atoms in a molecular entity has a profound influence on its chemical and physical properties. Here we describe a previously unclassified fundamental form of conformational isomerism through four resolved stereoisomers of a transoid (BF)O(BF)-quinoxalinoporphyrin. These comprise two pairs of enantiomers that manifest structural relationships not describable within existing IUPAC nomenclature and terminology. They undergo thermal diastereomeric interconversion over a barrier of 104 ± 2 kJ mol, which we term 'akamptisomerization'. Feasible interconversion processes between conceivable synthesis products and reaction intermediates were mapped out by density functional theory calculations, identifying bond-angle inversion (BAI) at a singly bonded atom as the reaction mechanism. We also introduce the necessary BAI stereodescriptors parvo and amplo. Based on an extended polytope formalism of molecular structure and stereoisomerization, BAI-driven akamptisomerization is shown to be the final fundamental type of conformational isomerization.

Cyclic tetrapeptides have generated great interest because of their broad-ranging biological properties. In order to synthesize these highly strained 12-membered cyclic compounds, a cyclization strategy using pseudoprolines as removable turn inducers has been developed. The pseudoproline derivatives induce a cisoid amide bond in the linear peptide backbone which facilitates cyclization. After cyclization, the turn inducers can be readily removed to afford cyclic tetrapeptides containing serine or threonine residues.

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Aryl amines are synthesized from halobenzenes via copper mediated reactions employing sodium azide under mild conditions in ethanol/water. The reaction proceeds stepwise via the aryl azide, which is reduced to the corresponding amine in‐situ. The methodology allows syntheses of amines from corresponding para‐, meta‐ and ortho‐bromobenzenes bearing electron withdrawing groups. Bifunctional halobenzenes bearing alkanoyl chains with terminal bromides are selectively transformed, generating an aniline and an aliphatic azide, as this azide position is stable to reduction. A one‐pot multistep sequence for preparation of the target amines was designed. The azide formation is mediated by CuI while elemental Cu is generated simultaneously, which is deposited onto the employed PTFE stirring bar used in the reaction. The Cu films were quantified and analysed by SEM/EDS. The Cu, either deposited or in solution, is responsible for the azide reduction, possibly involving nitrene intermediates. An application of the modified stirring bars as a heterogeneous catalyst for a click reaction is demonstrated.