The synthesis of iodolopyrazolium salts via an oxidative cyclization of 3-(2-iodophenyl)-1H-pyrazoles is described. The reaction is characterized by a broad substrate scope and various applications of these novel cyclic iodolium salts acting as useful synthetic intermediates are demonstrated, in particular in site-selective ring-openings. This was finally applied to generate derivatives of the anti-inflammatory drug celecoxib. Their application as highly active halogen bonding donors is shown as well.

Two one-pot procedures for the construction of O- and N-bridged diaryliodonium triflates are described. An effective aryne-mediated arylation of o-iodophenols and -sulfonamides provides diarylether and diarylamine intermediates, which are subsequently oxidized and cyclized to the corresponding diaryliodaoxinium and -iodazinium salts. Different derivatizations were applied to demonstrate their capacity as useful building blocks and gain a deeper understanding toward the general reactivity of these underdeveloped but potentially highly useful compounds.

The first directing-group-mediated C-H alkenylation with alkenyl-λ-iodanes as electrophilic alkene-transfer reagents has been developed. The application of free aromatic amines as challenging but synthetically valuable directing groups in combination with an Ir catalyst enabled the synthesis of highly desirable 1,3-dienes in excellent yields of up to 98% with high to perfect (Z,E) stereoselectivity. A broad substrate scope and further synthetic modifications are demonstrated.

C-C triple bonds are amongst the most versatile functional groups in synthetic chemistry. Complementary to the Sonogashira coupling the direct metal-catalyzed alkynylation of C-H bonds has emerged as a highly promising approach in recent years. To guarantee a high regioselectivity suitable directing groups (DGs) are necessary to guide the transition metal (TM) into the right place. In this Focus Review we present the current developments in DG-mediated C(sp )-H and C(sp )-H modifications with terminal alkynes under oxidative conditions and with electrophilic alkynylation reagents. We will discuss further modifications of the alkyne, in particular subsequent cyclizations to carbo- and heterocycles and modifications of the DG in the presence of the alkyne.

Two one-pot procedures for the construction of carbon-bridged diaryliodonium triflates and tetrafluoroborates are described. Strong Brønsted acids enable the effective Friedel− Crafts alkylation with diversely substituted o-iodobenzyl alcohol derivatives, providing diphenylmethane scaffolds, which are subsequently oxidized and cyclized to the corresponding dibenzo-[b,e]iodininium salts. Based on NMR investigations and density functional theory (DFT) calculations, we could verify the so-farundescribed existence of two stable isomers in cyclic iodonium salts substituted with aliphatic side chains in the carbon bridge. Article pubs.acs.org/joc