Tandem Hock and Friedel-Crafts reactions allowing an expedient synthesis of a cyclolignan-type scaffold.

The Hock cleavage, which is compatible with tandem processes, was applied to the synthesis of 1-aryltetralines through a one-pot transformation from readily available benzyl(prenyl)malonate substrates. After the photooxygenation of the prenyl moiety, the resulting hydroperoxide was directly engaged in a Hock cleavage by adding a Lewis acid. The presence of an aromatic nucleophile in the reaction mixture and that of a benzyl moiety on the substrate resulted in tandem Friedel-Crafts reactions to form the 1-aryltetraline products. These compounds share a close analogy to the cyclolignan natural products. Experimental observations and a DFT study support the involvement of an aldehyde intermediate during the Friedel-Crafts reactions, rather than an oxocarbenium.

Tandem InCl3-Promoted Hydroperoxide Rearrangements and Nucleophilic Additions: A Straightforward Entry to Benzoxacycles.

The acid-catalyzed rearrangement of organic peroxides is generally associated with C-C-bond cleavages (Hock and Criegee rearrangements), with the concomitant formation of an oxocarbenium intermediate. This article describes the tandem process between a Hock or Criegee oxidative cleavage and a nucleophilic addition onto the oxocarbenium species (in particular a Hosomi-Sakurai-type allylation), under InCl3 catalysis. It was applied to the synthesis of 2-substituted benzoxacycles (chromanes and benzoxepanes), including a synthesis of the 2-(aminomethyl)chromane part of sarizotan, and a total synthesis of erythrococcamide B.

Alkyliodines in High Oxidation State: Enhanced Synthetic Possibilities and Accelerated Catalyst Turn-Over.

In contrast to aryliodine(III) compounds, which have matured into a particularly attractive class of oxidants in modern synthesis, the synthetic potential of related alkyliodine(III) derivatives has remained widely underestimated. This is surprising since several unique synthetic possibilities arise directly from the low stability of their central carbon-iodine bond. In this respect, these high-oxidation-state iodine compounds resemble environmentally benign variants of the prominent metal counterparts such as those derived from palladium, nickel and copper. This Concept article summarizes the general reactivity trends in alkyliodine(III) chemistry and discusses selected examples of their strategic use as highly reactive, transient species in organic synthesis and homogeneous catalysis.

Intermolecular Radical C(sp3 )-H Amination under Iodine Catalysis.

The direct amination of aliphatic C-H bonds has remained one of the most tantalizing transformations in organic chemistry. Herein, we report on a unique catalyst system, which enables the elusive intermolecular C(sp3 )-H amination. This practical synthetic strategy provides access to aminated building blocks and fosters innovative multiple C-H amination within a new approach to aminated heterocycles. The synthetic utility is demonstrated by the synthesis of four relevant pharmaceuticals.

Multiple Halogenation of Aliphatic C-H Bonds within the Hofmann-Löffler Manifold.

An innovative approach to position-selective polyhalogenation of aliphatic hydrocarbon bonds is presented. The reaction proceeded within the Hofmann-Löffler manifold with amidyl radicals as the sole mediators to induce selective 1,5- and 1,6-hydrogen-atom transfer followed by halogenation. Multiple halogenation events of up to four innate C-H bond functionalizations were accomplished. The broad applicability of this new entry into polyhalogenation and the resulting synthetic possibilities were demonstrated for a total of 27 different examples including mixed halogenations.

Iodine(III)-Mediated Selective Intermolecular C-H Amination for the Chemical Diversification of Tryptamines.

Defined hypervalent iodine reagents of the general structure PhI[N(SO2R)(SO2R')]2 promote the selective direct C-H-amination of the indole core of various tryptamines. Starting from a general C2-amination strategy, subsequent transformations enable a variety of site-selective functionalizations, which proceed with noteworthy high chemoselectivity and provide an overall access to structurally diversified products.

Towards Uniform Iodine Catalysis: Intramolecular C-H Amination of Arenes under Visible Light.

A photochemical catalytic amination of arenes is presented. The reaction proceeds under benign iodine catalysis in the presence of visible light as the initiator and provides access to a range of differently substituted arylamines. A total of 29 examples demonstrate the broad applicability of this mild oxidation method. The scope of the reaction could further be expanded to silyl-tethered derivatives, which undergo intramolecular amination upon formation of seven-membered heterocycles. Cleavage of the silicon tether provides access to the corresponding 3-substituted anilines.