Substituted 2-aminobiphenyls have been prepared from arylhydrazines and anilines via radical arylation reactions under simple oxidative conditions. The strong directing effect of the free and unprotonated amino functionality leads to high regioselectivities, and anilines have been shown to be significantly better aryl radical acceptors than nitrobenzenes or phenyl ethers. The methodology is also applicable to phenols, which react best as phenolates under strongly basic conditions. Finally, radical arylation reactions of anilines and anilinium salts under various conditions have for the first time demonstrated that regioselectivity can also be controlled through the rearomatization step and that the addition of an aryl radical to a substituted benzene might even be reversible.

tert-Butyl phenylazocarboxylates are versatile building blocks for synthetic organic chemistry. Nucleophilic substitutions of the benzene ring proceed with aromatic amines and alcohols under mild conditions. The attack of aliphatic amines may be directed to the aromatic core as well as to the carbonyl unit leading to azocarboxamides. The benzene ring can further be modified through radical reactions, in which the tert-butyloxycarbonylazo group enables the generation of aryl radicals at either elevated temperatures or under acidic conditions. Radical reactions include oxygenation, halogenation, carbohalogenation, carbohydroxylation, and aryl-aryl coupling.

Substituted 2-aminobiphenyls have been prepared from arylhydrazine hydrochlorides and anilines in biphasic radical arylation reactions with dioxygen from air as a most simple and readily available oxidant. Under optimized conditions, the free amino functionality of the aniline leads to high ortho:meta regioselectivities, now even for anilines bearing a donor substituent in the para position. Finally, the mild and metal-free new access to aminobiphenyls was shown to be applicable on a gram scale.

In the current work, we have documented the use of two complementary supramolecular motifs, namely multipoint hydrogen bonding and metal complexation, as a means to control the stepby-step assembly of a panchromatically absorbing and highly versatile solar energy conversion system. On one hand, two different perylenediimides (1a/1b) have been integrated together with a metalloporphyrin (2) by means of the Hamilton receptor/cyanuric acid hydrogen bonding motif into energy transduction systems 1a•2 or 1b•2. Steady-state and time-resolved measurements corroborated that upon selective photoexcitation of the perylenediimides (1a/1b), an energy transfer evolved from the singlet excited state of the perylenediimides (1a/1b) to that of the metalloporphyrin (2). On the other hand, fullerene (3) and metalloporphyrin (2) form the electron donor-acceptor system 2•3 via axial complexation. Photophysical measurements confirm that an electron transfer prevails from the singlet excited state of 2 to the electron-accepting 3. The correspondingly formed radical ion pair state decays with a lifetime of 1.0 AE 0.1 ns. As a complement to the aforementioned, the energy transduction features of 1a•2 were combined with the electron donor-acceptor characteristics of 2•3 to afford 1a•2•3. To this end, time-resolved measurements reveal that the initially occurring energy-transfer interaction (53 AE 3 ps) between 1a/1b and 2 is followed by an electron transfer (12 AE 1 ps) from 2 to 3. From multiwavelength analyses, the lifetime of the radical ion pair state in 1a•2•3-as a product of a cascade of light-induced energy and electron transfer-was derived as 3.8 AE 0.2 ns. I n recent years, the conversion of solar energy into electrical energy has been one of the most important areas of scientific research due to the constantly growing human energy demands (1, 2). In order to design efficient, low-cost, environmentally responsible artificial photosynthetic systems, research follows the concepts of nature (3, 4). Similar to natural photosynthetic organisms (5-8), artificial systems undergo cascades of light-induced energy and electron transfer reactions. The absorbed energy is converted into chemical potential energy in the form of a radical ion pair state (9). These events take place in organized arrays of photofunctional chromophores within specifically tailored environments that allow an efficient light harvesting. As an important prerequisite, the lifetime of the excited states should be long enough to power efficient electron transfer in order to obtain radical ion pair states. Therefore, the development of panchromatically absorbing molecules with appropriate absorptive properties for light harvesting is desirable.Owing to their biological relevance and favorable properties as natural chromophores, porphyrinoids are widely used as molecular components in artificial photosynthetic systems. Their functions include panchromatic light harvesting through most of the visible part of the solar spectrum and electron transport (10-26). As another m...

We report a new carbooxygenation‐type version of the Meerwein arylation in which the introduction of oxygen is achieved by using dioxygen from the air. In this way, hydroperoxides were obtained from activated as well as non‐activated alkenes by oxidizing aryl hydrazines with manganese dioxide. The best results were obtained with α‐substituted acrylates. Importantly, the aryl hydrazine has to be added slowly to the reaction mixture to allow sufficient uptake of dioxygen from the air. Competition and labeling experiments revealed hydroperoxyl radicals as novel oxygen‐centered radical scavengers.