Metal Complexes with Macrocyclic Ligands,VI. The role of substituents on the complexation rate of transition metal ions with several 1,4,7,10-tetraazacyclotridecanes

12,12-Dimethyl-1,4,7,10-tetraazacyclotridecane (I), 11,13-dimethyl-1,4,7,10-tetraazacyclotridecane (II), 11,11,13-trimethyl-1,4,7,10-tetraazacyclotridecane (III) and 1,4,7,10,12,12-hexamethyl-1,4,7,10-tetraazacyclotridecane (IV) have been synthesized and their properties are described. While the Ni²⁺ and Cu²⁺ complexes of I–III have square planar geometries, those of IV are pentacoordinate according to their absorption spectra. Similarly, while the Co²⁺ complex of I is octahedral and readily oxygenated, the analogous complex with IV is pentacoordinate and not sensitive to oxygen. The rate of complexation of these ligands with Cu²⁺ and Ni²⁺ decreases in the order I > II > III ? IV, indicating that the number as well as the position of the methyl groups are important. Finally for Cu²⁺ the formation of the thermodynamic stable end product is slown down by methyl substitution in α-position to the coordinating nitrogen atoms (ligand II and III) so that an intermediate can be observed, whereas with I Cu²⁺ directly forms the end product.     

1, 6-Addition von Chlorsulfonylisocyanat. Vorläufige Mitteilung

A 1, 6-addition of sulfonyl chloride isocyanate to 5, 7-dimethyl-8-methylidene-tricyclo[3.2.1.0^2,7]oct-3-en-6-one ( 1 ) produced the new tricyclic skeleton of 4a, 6-dimethyl-2, 5-dioxo-2, 3, 4a, 5, 6, 8a-hexahydro-1H-6, 4-methenoquinoline-1-sulfonyl chloride ( 2 ). The structure of the new aza-tricyclic species has been elucidated by X-ray analysis.     

Dimerisierung von benzocyclobuten zu 1-ethyl-9,10-dihydrophenanthren unter dem einfluss von natrium-kalium-legierung in tetrahydrofuran

Benzocyclobutene is cleaved by sodium-potassium alloy in THF at a C_aryl-CH₂ bond whereby in contrast to the corresponding reaction with lithium a dimeric product, 1-ethyl-9,10-dihydrophenanthrene, is formed.     

Combinatorial Solid-Phase Synthesis of Structurally Complex Thiazolylhydantoines

A nine-step (!) solid-phase synthesis and subsequent cleavage with cyclization from the polymeric support were the keys to preparing high-quality molecular libraries of thiazolylhydantoines 1 from modified amino acid building blocks. Each step in the synthesis is different. Because the final cyclization cleaves only molecules that have been successfully constructed, the products obtained are pure. R¹, R²=alkyl; R³=aryl, arylO; R⁴=allyl.     

On-Surface Synthesis of Polyphenylene Wires Comprising Rigid Aliphatic Bicyclo[1.1.1]Pentane Isolator Units

Bicyclo[1.1.1]pentane (BCP) motifs are of growing importance to the pharmaceutical industry as sp³-rich bioisosteres of benzene rings and as molecular building blocks in materials science. Herein we explore the behavior of 1,3-disubstituted BCP moieties on metal surfaces by combining low-temperature scanning tunneling microscopy / non-contact atomic force microscopy studies with density functional theory modeling. We examine the configuration of individual BCP-containing precursors on Au(111), their supramolecular assembly and thermally activated dehalogenative coupling reactions, affording polymeric chains with incorporated electronically isolating units. Our studies not only provide the first sub-molecular insights of the BCP scaffold behavior on surfaces, but also extend the potential application of BCP derivatives towards integration in custom-designed surface architectures.