A new metal-free method for the rapid and productive preparation of indoles has been developed. This process is based on sterically congested hypervalent iodine compounds of the family of Koser reagents, and iodosobenzene in combination with 2,4,5-tris-isopropylbenzene sulfonic acid provides the highest yields and fastest reaction times. This reagent alone promotes the chemoselective oxidative cyclization of 2-amino styrenes to indoles in high yields under mild conditions.

α-Tertiary amines (ATAs) are attractive structural motifs that are frequently found in biologically active molecules. Therefore, the development of an efficient method for the synthesis of ATAs represents an important research topic in the field of medicinal chemistry as well as organic chemistry. Although the Ritter reaction is a reliable approach for preparing α-tertiary amine derivatives via intermolecular amination reactions, the typical methods suffer from disadvantages such as harsh reaction conditions and the use of strong acids. Because of this, it has been of limited use in the synthesis of ATAs. We report here on the decarboxylative Ritter-type amination of carboxylic acids bearing an α-quaternary carbon center using a combination of PhI(OAc) and molecular iodine (I) to produce the corresponding α-tertiary amine derivatives. This reaction proceeded at ambient temperature on the benchtop with a fluorescent light. Mechanistic investigations suggest that the reaction proceeds via the formation of an alkyl iodide and a higher oxidation state iodine(III) species as key intermediates. Similarly, a stepwise protocol for the Ritter-type amination of alcohols via the formation of oxalic acid monoalkyl esters was also achieved. The present methods represent a useful tool for the synthesis of ATAs that are difficult to prepare by conventional methods.

The stability constants of complexes of the macrocyclic ligand do3a‐pic4– (H4do3a‐pic = 2,2′,2″‐{10‐[(6‐carboxypyridin‐2‐yl)methyl]‐1,4,7,10‐tetraazacyclododecane‐1,4,7‐triyl}triacetic acid) with several divalent metal ions (Pb2+, Cd2+, Zn2+, Cu2+, Ca2+, and Mg2+) have been determined by using pH‐potentiometric titrations (I = 0.1 M KCl, 25 °C). The stability of these complexes follows the trend Cu2+ > Cd2+ ≈ Pb2+ ≈ Zn2+ >> Ca2+ >> Mg2+. A particularly high stability constant has been determined for the Cu2+ complex [log KCuL = 23.20(4)]. Analysis of the titration curves indicate the presence of protonated forms of the complexes in solution, with protonation constants of log KM(HxL) = 6.9–2.0 (x = 1, 2, or 3). The structure of the complexes in solution has been investigated by using 1H and 13C NMR spectroscopy and DFT calculations performed in aqueous solution at the TPSSh/6‐31G(d) level. In the case of the Pb2+ and Cd2+ complexes, relativistic effects were considered with the use of relativistic effective core potentials. Calculations show that the complexes with the largest metal ions (Pb2+ and Ca2+) are nine‐coordinate, with their coordination polyhedra being best described as capped twisted square antiprisms. The Cd2+ and Mg2+ complexes are seven‐coordinate, with the metal ions being bound to the four nitrogen atoms of the cyclen unit and the three acetate pendant arms. Finally, in the Cu2+ and Zn2+ complexes, the metal ions are six‐coordinated, with the metal ions being asymmetrically placed inside the macrocyclic cavity of the ligand, and the coordination polyhedra can be described as an octahedron and a trigonal prism, respectively.

A procedure for the intermolecular enantioselective dearomatization of phenols under chiral (I/III) catalysis is reported. This protocol employs 3-chloroperoxybenzoic acid (m-CPBA) as the terminal oxidant together with a defined C 2-symmetric aryl iodide as the effective organocatalyst. This enantioselective reaction proceeds with complete selectivity under mild conditions and enables the hydroxylative dearomatization of a number of phenols to give the corresponding p-quinol products with up to 50% ee.

Cu/Pd-catalyzed alkyne allylboration with racemic allylic carbonates proceeds with total inversion of configuration. Preliminary studies show that this synergistic catalysis can be used to perform a dynamic asymmetric allylic alkenylation that provides enantioenriched carboboration products.

An intramolecular approach towards the regioselective construction of 2,3-diarylated indoles is reported. The reaction follows an intramolecular electrophilic N-H and C-H bond functionalization between the aniline and acetylene. This methodology employs the concept of a traceless tether to provide access to the free 2,3-diarylated indole products comprising a total of 18 examples. Hypervalent iodine reagents were identified as suitable promoters and four different protocols are provided, including stoichiometric and catalytic transformations.

Synergistic bimetallic catalysis has become a very efficient tool for the selective carboboration of unsaturated hydrocarbons. This synthetic approach is based on the use of a catalytically generated boron-substituted organocopper nucleophile in a cross-coupling reaction catalyzed by a second transition metal. This way, hydrocarbons can be used as pro-nucleophiles in this type of transformations thus rendering a clean and operationally simple alternative to the traditional cross-coupling methodologies. This review provides a summary of the developments on this topic and discusses both the synthetic utility and mechanisms of these reactions.1 Introduction2 Carboboration of Alkenes via Synergistic Catalysis3 Carboboration of 1,3-Dienes via Synergistic Catalysis4 Carboboration of Alkynes via Synergistic Catalysis5 Conclusions

Eine neue Methode unter metallfreien Bedingungen zur schnellen und produktiven Synthese von Indolen wurde entwickelt. Dieser Prozess beruht auf einer voluminçsen Iodverbindung der Familie der Koser-Reagentien, wobei die Kombination aus Iodosobenzol und 2,4,5-Tris(isopropyl)benzolsulfonsäure die hçchsten Ausbeuten und kürzesten Reaktionszeiten gewährleistet. Dieses Reagens vermittelt die chemoselektive oxidative Cyclisierung von 2-Vinylanilinen zu Indolen in hohen Ausbeuten und unter milden Reaktionsbedingungen.Schema 1. Intramolekulare Aminierung von Alkenen mit hypervalenten Iod(III)-Reagentien.