Dirk Michalik

Copper‐Catalyzed Alkylation of Sulfonamides with Alcohols

the Chinese Academy of Sciences;the DFG (SPP 1118 and Leibniz Prize), and the BMBF. F. Shi thanks the Alexander-von-Humboldt-Stiftung for an AvH Fellowship

Ruthenium‐catalyzed Selective Monoamination of Vicinal Diols

The monoamination of vicinal diols in the presence of in situ generated ruthenium catalysts has been investigated. Among the various phosphines tested in combination with [Ru(3)(CO)(12)], N-phenyl-2-(dicyclohexyl-phosphanyl)pyrrole showed the best performance. After optimization of the reaction conditions this system was applied to different secondary amines and anilines as well as a number of vicinal diols. With the exception of ethylene glycol, monoamination of the vicinal diols occurred selectively and the corresponding amino alcohols were obtained in good yields, producing water as the only side product.

Ruthenium-Catalyzed Selective α,β-Deuteration of Bioactive Amines

A novel and convenient protocol for the catalytic hydrogen-deuterium exchange of biologically active tertiary amines utilizing the borrowing hydrogen methodology has been developed. In the presence of the readily available Shvo catalyst, excellent chemoselectivity toward α- and β-protons with respect to the nitrogen atom as well as high degree of deuterium incorporation and functional group tolerance is achieved. This allowed for the deuteration of complex pharmaceutically interesting substrates, including examples for actual marketed drug compounds. Notably, this method constitutes a powerful tool for the generation of valuable internal standard materials for LC-MS/MS analyses highly demanded for various life-science applications.

Platinum-Catalyzed Intramolecular Cyclizations of Alkynes: Efficient Synthesis of Pyrroloazepinone Derivatives†

Transition-metal-catalyzed cyclizations of aromatic and heteroaromatic compounds with alkynes have attracted much attention in the last decade. In particular, intramolecular goldand platinum-catalyzed hydroarylations, cycloisomerizations, and cycloadditions offer new ways for the efficient construction of biologically interesting carboand heterocycles. Recent elegant examples also include the use of N-heterocycles; for example, Echavarren et al. and England and Padwa reported intramolecular cyclizations of indol derivatives in the presence of gold catalysts. Inspired by this work and our interest in the application of catalytic coupling and amination reactions for the synthesis of bio-active compounds, we started a program on the catalytic synthesis of novel pyrroloazepinone derivatives. The pyrroloazepinone motif (Scheme 1) is present in a variety of natural and pharmaceutical products, such as hymenialdisine, stevensine, latonduine, and the paul-

Phosphorus Speciation in Agro-Industrial Byproducts: Sequential Fractionation, Solution 31P NMR, and P K- and L2,3-Edge XANES Spectroscopy

Little is known about P species in agro-industrial byproducts from developing countries, which may be either pollutants or valuable soil amendments. The present study speciated P in dry (COD) and wet (COW) coffee, sisal (SIS), barley malt (BEB) and sugar cane processing (FIC) byproducts, and filter cakes of linseed (LIC) and niger seed (NIC)with sequential fractionation, solution (31)P nuclear magnetic resonance (NMR) spectroscopy, and P K- and L(2,3)-edge X-ray absorption near-edge structure (XANES) spectroscopy. The sequential P fractionation recovered 59% to almost 100% of total P (P(t)), and more than 50% of P(t) was extracted by H(2)O and NaHCO(3) in five out of seven samples. Similarly, the NaOH + EDTA extraction for solution (31)P NMR recovered 48-94% of P(t). The (31)P NMR spectra revealed orthophosphate (6-81%), pyrophosphate (0-10%), and orthophosphate monoesters (6-94%). Orthophosphate predominated in COD, COW, SIS, and FIC, whereas BEB, UC, and NIC were rich in orthophosphate monoesters. The concentrations of P(i), and P(o) determined in the sequential and NaOH + EDTA extractions and (31)P NMR spectra were strongly and positively correlated (r = 0.88-1.00). Furthermore, the P K- and L(2,3)-edge XANES confirmed the H(2)SO(4)--P(i) detected in the sequential fractionation by unequivocal identification of Ca--P phases in a few samples. The results indicate that the combined use of all four analytical methods is crucial for comprehensive P speciation in environmental samples and the application of these byproducts to soil.

Efficient and Selective Telomerization of 1,3-Butadiene with Diols Catalyzed by Palladium–Carbene Complexes

The selective telomerization of 1,3-butadiene with seven different linear and cyclic diols proceeds in the presence of in situ generated palladium carbene catalysts. By applying optimized reaction conditions, including very low metal loadings (2-10 ppm), excellent catalyst turnover numbers (>250,000) and good chemoselectivities are observed with respect to the mono-octadienyl ether derivatives. This protocol allows the efficient preparation of unsaturated alcohols, which are useful for various applications.

Ecophysiological performance of the primitive red alga Dixoniella grisea (Rhodellophyceae) to irradiance, temperature and salinity stress: growth responses and the osmotic role of mannitol

A. Eggert, S. Raimund, D. Michalik, J. West and U. Karsten. 2007. Ecophysiological performance of the primitive red alga Dixoniella grisea (Rhodellophyceae) to irradiance, temperature and salinity stress: growth responses and the osmotic role of mannitol. Phycologia 46: 22–28. DOI: 10.2216/06-12.1 A culture strain of the benthic unicellular red alga Dixoniella grisea was investigated under different stress conditions. The effects of salinity, temperature and irradiance on growth rates were examined in two-factorial experiments and the accumulation of mannitol in response to increasing salinity investigated. The strain grows in a broad salinity range, from brackish water to twice seawater (60 psu). At optimal salinity (10 psu) and optimal temperature conditions (25–30°C), D. grisea grew best at moderate photon flux densities (PFDs; 50–100 μmol photons m−2 s−1). However, interactive effects between all factors were present. At suboptimal salinities and temperatures, maximal growth rates were shifted to lower PFD and growth was considerably reduced at 50 and 100 μmol photons m−2 s−1. The polyol mannitol was the main low molecular weight carbohydrate in D. grisea. This was verified by 13C-nuclear NMR spectroscopy and HPLC analysis. Mannitol levels increased from 2 to 52 μmol g−1 dry weight (dw) with increasing salinities between 10 and 60 psu, indicating its role as an osmolyte for the first time in a unicellular red alga.

When Like Charged Ions Attract in Ionic Liquids: Controlling the Formation of Cationic Clusters by the Interaction Strength of the Counterions.

The properties of ionic liquids are described by a subtle balance between Coulomb interaction, hydrogen bonding, and dispersion forces. We show that lowering the attractive Coulomb interaction by choosing weakly coordinating anions leads to the formation of cationic clusters. These clusters of like-charged ions are stabilized by cooperative hydrogen bonding and controlled by the interaction potential of the anion. IR and NMR spectroscopy combined with computational methods are used to detect and characterize these unusual, counter-intuitively formed clusters. They can be only observed for weakly coordinating anions. When cationic clusters are formed, cyclic tetramers are particularly stable. Therein, cooperative hydrogen-bond attraction can compete with like-charge repulsion. We present a simple but effective spectroscopic scale for the possibility of like-charge attraction in ionic liquids, based on IR and NMR signatures.

Selective Rhodium‐Catalyzed Reduction of Tertiary Amides in Amino Acid Esters and Peptides

Efficient reduction of the tertiary amide bond in amino acid derivatives and peptides is described. Functional group selectivity has been achieved by applying a commercially available rhodium precursor and bis(diphenylphosphino)propane (dppp) ligand together with phenyl silane as a reductant. This methodology allows for specific reductive derivatization of biologically interesting peptides and offers straightforward access to a variety of novel peptide derivatives for chemical biology studies and potential pharmaceutical applications. The catalytic system tolerates a variety of functional groups including secondary amides, ester, nitrile, thiomethyl, and hydroxy groups. This convenient hydrosilylation reaction proceeds at ambient conditions and is operationally safe because no air-sensitive reagents or highly reactive metal hydrides are needed.

Lewis-acid-assisted methyl exchange reactions in silylated aminodichloroarsanes.

Lewis-acid-assisted methyl/chlorine, methyl/azide, and methyl/triflate exchange reactions between silicon and arsenic centers have been studied and applied to different silylated aminoarsane species leading to a number of new methylarsane compounds: bis(trimethylsilyl)amino(dichloro)arsane (3) was reacted with GaCl(3) yielding a bis(chlorodimethylsilyl)-tetramethyl-cyclo-disilazane (4) accompanied by the release of Me(2)AsCl, while trimethylsilyl(m-terphenyl)amino(dichloro)arsane (5) (m-terphenyl = 2,6-Mes(2)-C(6)H(3), Mes = 2,4,6-Me(3)C(6)H(2)) reacted with GaCl(3) to give dichloromethylsilyl(m-terphenyl)aminodimethylarsane (6). In the presence of trimethylsilylazide, trimethylsilyl(m-terphenyl)amino(dichloro)arsane displays a methyl/azide exchange triggered by the action of GaCl(3) yielding azidodimethylsilyl(m-terphenyl)amino(chloro)methylarsane (7). Moreover, methyl/triflate exchange reactions have been observed in the reaction of trimethylsilyl(m-terphenyl)amino(dichloro)arsane (i) with 1 equiv of AgOTf (OTf = triflate) yielding N-(trifluoromethylsulfonatodimethylsilyl)-N-(m-terphenyl)amino(methyl)chloroarsane (8) and (ii) with 2 equiv of AgOTf yielding N-(trifluoromethylsulfonatodimethylsilyl)-N-(m-terphenyl)trifluoromethylsulfonatomethylarsane (9). All new compounds (3-9) have been fully characterized by means of vibrational spectroscopy, X-ray, CHN analysis, MS, and NMR studies. A possible reaction mechanism is discussed starting from an initial chloride abstraction and the intermediate formation of a cationic iminoarsane species. In a second step, a methyl shift from the silicon to the arsenic center occurs.