Studies of xenobiotic disposition in rodents often employ experimental designs using differing routes of administration. In an effort to investigate the effects of route of administration on enantioselective disposition of xenobiotics, a chiral polychlorinated biphenyl (PCB), racemic PCB 136, was administered as a single dose (50 mg/kg body weight) to male or female C57BL/6 mice either orally or via intraperitoneal injection. Mice were sacrificed after either 3 or 6 days, and blood and organs were collected for PCB analysis. Intraperitoneal injection of PCB 136 produced statistically higher PCB levels in blood and organs than did the oral administration. Tissue levels were higher after 3 days than those after 6 days. Enantioselective analysis showed that (+)-PCB 136 was enriched in most organs, with the most pronounced enrichment found in the liver and the brain of animals dosed orally or by intraperitoneal injection, respectively. Significantly higher retained enantiomeric fractions of PCB 136 were found in the oral treatment groups compared with those found in intraperitoneal treatment groups, possibly as a result of the lower PCB levels in oral treatment groups. Therefore, the choice of administration route may well have implications for the enantioselective disposition of PCB 136 and other chiral substances.

A practical synthesis of a novel class of phosphine ligands, phosphino substituted N-aryl pyrroles (PAP ligands), has been developed. These ligands are applied in the palladium-catalyzed coupling of a variety of aryl and heteroaryl chlorides with phenylboronic acid showing exceedingly high turnover numbers at mild reaction temperatures and even at room temperature.

The iron-catalyzed reduction of aromatic nitro compounds to the corresponding anilines applying organosilanes is reported. In the presence of FeX(2)-R(3)P catalysts a series of nitroarenes is selectively reduced tolerating a wide range of functional groups.

Dedicated to Professor Wolfgang A. Herrmann on the occasion of his 60th birthday Noteworthy efforts have been devoted to the development of efficient catalytic asymmetric reductions employing benign and environmentally available biometals such as iron, zinc, and copper. The preparation of enantiomerically pure secondary alcohols is of special significance because these intermediates constitute valuable building blocks for the manufacture of pharmaceuticals, agrochemicals, and advanced materials.[1] Catalytic asymmetric hydrogenation of prochiral ketones is the most direct route to optically active alcohols, [2] however, hydrosilylation of carbon-carbon and carbonheteroatom bonds is a promising alternative to asymmetric hydrogenation because of the mild conditions and operational simplicity.[3]The earliest reports on hydrosilylation appeared three decades ago, [4] and known asymmetric hydrosilylations of prochiral ketones rely on precious metals such as rhodium, [5] ruthenium, [6] and iridium. [7] Less expensive metals such as titanium, [8] zinc, [9] tin, [10] and copper [11] have also been explored. Each method has its virtues as well as its limitations. The limitations include either the cost of the metal catalyst, the toxicity of the residual metal in the product, the operational difficulties (e.g. low temperatures ranging from À50 to À70 8C), or the use of complex ligand systems.Recently, we started a program to develop more sustainable catalysts by replacing precious metals with nonprecious metals. In accord with the concept of "cheap metals for noble tasks", [12] the possible uses of iron catalysts are especially attractive.[13] Iron is the second most abundant metal available and plays an important role in biology.[14] Despite the many advantages and recent attention [15] to iron catalysis, it remains undeveloped compared to other transition metals (e.g. Ru, Rh, Pd, and Ir etc.), particularly in the field of asymmetric catalysis. To the best of our knowledge there is only one report by Nishiyama ând Furuta [16] on the development of iron-catalyzed asymmetric hydrosilylation. They used multidentate nitrogen ligands and reported enantioselectivities of up to 79 %. The scope of this work can be expanded; herein, we disclose our results on an improved and general ironcatalyzed asymmetric hydrosilylation of ketones (Table 1).Our recent study on the hydrosilylation of aldehydes revealed that Fe(OAc) 2 in the presence of electron-rich phosphine ligands and hydrosilanes forms an active catalyst.[17] On the basis of these findings we turned our attention to the asymmetric reduction of ketones.Initially, several chiral ligands were tested for the reduction of acetophenone to 1-phenylethanol by using a given set of conditions and selected phosphines (Table 1 and Figure 1). Privileged ligands such as (S)-2,2'-bis(diphenyl-, (S,S)-l-benzyl-3,4-bis-(diphenylphosphino)pyrrolidine ((S,S)-deguphos), and binaphthyl derived systems, such as L1 and L2, gave good to excellent conversions of acetophenone (68-99 %), but poor enan...

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A general and highly chemoselective hydrosilylation of aldehydes using iron catalysts is reported. Fe(OAc)2 in the presence of tricyclohexylphosphine as ligand and polymethylhydrosiloxane (PMHS) as an economical hydride source forms an efficient catalyst system for the hydrosilylation of a variety of aldehydes. Aryl, heteroaryl, alkyl and alpha,beta-unsaturated aldehydes are successfully reduced to the corresponding primary alcohols. Broad substrate scope and high tolerance against several functional groups make the process synthetically useful.

CO 2 tBu HO CO 2 H HO CO 2 R O CO 2 Me HO O CO 2 tBu OH H H ( ) 7 22 ( ) 7 ( ) 7 1 R = H 26 R = Me (Ph 3 PC 3 H 7 )Br, KHMDS, THF/HMPT, -78°C→RT 23 24 ( ) 7 25 KOH, MeOH 82 % PDC, CH 2 Cl 2 71 % PDC, CH 2 Cl 2 50 %, 30 % after MPLC 1. KOH, MeOH 2. CH 2 N 2 ( ) 7 DIBAL-H, PhMe/THF, -78°C 91 % 20 98 % 55-76 % Scheme 5. Synthesis of 12-OPDA (1) and 12-OPDA methyl ester (26). DIBAL-H ¼ diisobutylaluminum hydride, KHMDS ¼ potassium hexamethyldisilazanide, HMPT ¼ hexamethylphosphoric acid triamide, PDC ¼ pyridinium dichromate.

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