Most present-day semiconductor devices use inorganic crystalline materials, with single-crystalline silicon dominating other materials like GaAs by about a factor of 1000. Despite the advantages of single-crystalline inorganic semiconductors like high room-temperature mobility (up to 1000 cm2/(V s)) and high stability, these materials are less suitable for low-cost and large-area applications. Additionally, silicon is an indirect semiconductor and therefore is not well suited for optoelectronic applications like light-emitting diodes. Solar cells from silicon are expensive and require a large amount of energy for their fabrication, leading to a long energy payback time. As an alternative, organic semiconductors have recently gained much attention (for review articles, see refs 1 -3 (OLEDs), ref 4 (organic electronics in general), and refs 5 and 6 (organic solar cells)). Originally, much of the research concentrated on single crystals, which can have mobilities of a few cm2/(V s) at room temperature and even much higher values at low temperature, as shown in the pioneering work of Karl et al.7 However, for practical applications, thinfilm organic semiconductors with disordered morphology, such as evaporated small-molecule compounds or polymers processed from solution, are prevailing. Organic semiconductors are already broadly applied as photoconductors for copiers and laser printers. * Corresponding author. E-mail: leo@iapp.de. Web address: www.iapp.de. 1233 Chem. Rev. 2007, 107, 1233−1271

Highly efficient organic devices based on electrically doped transport layers.

This account examines double asymmetric induction from theoretical and practical viewpoints. In the context of four major organic reactions-the aldol, Diels-Alder, catalytic hydrogenation, and epoxidation-it is shown that a double asymmetric induction can be analyzed in terms of the single asymmetric reactions of each of the two chiral reactants. A rule which qualitatively relates the results of these single asymmetric reactions with the outcome of the double asymmetric reaction is proposed. A powerful new strategy based on this rule for the predictable creation of new chiral centers is discussed and the use of this strategy for the synthesis of sugars and macrolides is presented.

Double Asymmetric Synthesis and a New Strategy for Stereochemical Control in Organic Synthesis

The addition of C-nucleophiles such as Grignard reagents or enolates to chiral α- or β-alkoxy aldehydes or ketones creates a new center of chirality and is therefore diastereogenic. In order to control stereoselectivity, two strategies have been developed: (1) Use of Lewisacidic reagents which form intermediate chelates, these being attacked stereoselectively from the less hindered side (chelation control); (2) use of reagents incapable of chelation, stereoselective attack being governed by electronic and/or steric factors (non-chelation control). Generally, the two methods lead to the opposite sense of diastereoselectivity. It is possible to predict the outcome by careful choice of organometallic reagents containing elements such as Li, Mg, B, Si, Sn, Cu, Zn, or Ti.

For corrigendum see DOI:10.1002/anie.198407461

Chelation or Non‐Chelation Control in Addition Reactions of Chiral α‐ and β‐ Alkoxy Carbonyl Compounds [New Synthetic Methods (44)]

Kinetic Isotope Effects in the Study of Organometallic Reaction Mechanisms

Computational Studies of Synthetically Relevant Homogeneous Organometallic Catalysis Involving Ni, Pd, Ir, and Rh: An Overview of Commonly Employed DFT Methods and Mechanistic Insights

Reduction of carbonyl compounds via hydrosilylation. 3. Asymmetric reduction of keto esters via hydrosilylation catalyzed by a rhodium complex with chiral phosphine ligands

Reduction of carbonyl compounds via hydrosilylation

Reduction of carbonyl compounds via hydrosilylation. 4. Highly regioselective reductions of .alpha.,.beta.-unsaturated carbonyl compounds

Asymmetric hydrogenation of prochiral olefins catalyzed by rhodium complexes with chiral pyrrolidinodiphosphines. Crucial factors for the effective asymmetric induction

Tetsuo Kogure

Papers

Reduction of carbonyl compounds via hydrosilylation. 3. Asymmetric reduction of keto esters via hydrosilylation catalyzed by a rhodium complex with chiral phosphine ligands

Reduction of carbonyl compounds via hydrosilylation

Reduction of carbonyl compounds via hydrosilylation. 4. Highly regioselective reductions of .alpha.,.beta.-unsaturated carbonyl compounds

Asymmetric hydrogenation of prochiral olefins catalyzed by rhodium complexes with chiral pyrrolidinodiphosphines. Crucial factors for the effective asymmetric induction

The action of tris(triphenylphosphine)chlororhodium on polyhydromonosilanes