Sauerstoff und Osmium – ein neues Paar für Dihydroxylierungen?

Wirth, Thomas

doi:10.1002/(sici)1521-3757(20000117)112:2<342::aid-ange342>3.0.co;2-z

Angewandte Chemie

2000

DOI: 10.1002/(sici)1521-3757(20000117)112:2<342::aid-ange342>3.0.co;2-z

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Sauerstoff und Osmium – ein neues Paar für Dihydroxylierungen?

Thomas Wirth¹

Abstract: Die Aktivierung von Sauerstoff in neuen Synthesemethoden erweitert das Spektrum Osmium‐katalysierter Dihydroxylierungen [Gl. (1)] beträchtlich. Sogar Luft kann nun als Cooxidationsmittel eingesetzt werden – fast ohne Selektivitätsverlust bei der asymmetrischen Version dieser Reaktion.

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Cited by 6 publications

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An Electrophilic Cleavage Procedure for the Asymmetric Dihydroxylation: Direct Enantioselective Synthesis of Cyclic Boronic Esters from Olefins

Hövelmann

Muñiz

2005

Chemistry A European J

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A variation within the osmium-catalysed asymmetric dihydroxylation (AD) of olefins is described that yields cyclic boronic esters from olefins in a straight-forward manner. This process represents the first real product alteration in asymmetric dihydroxylation, since all previous protocols lead to free diols exclusively. A protocol based on the Sharpless AD conditions (for enantioselective oxidation of prochiral olefins) was developed that gives cyclic boronic esters with excellent enantiomeric excesses (ee's). Some of the ee's are higher than those reported for conventional AD. The unprecedented role of phenyl boronic acid on the course of the AD reaction was investigated in detail. PhB(OH)2 does not interfere with the chiral ligand, leaving the enantioselective step of olefin oxidation intact. The main role of the boronic acids-apart from protecting the diol products against potential overoxidation-relies on removing the diol entity in an electrophilic cleavage, which is in contrast to the conventional hydrolytic cleavage of the AD protocols. Thus, a mechanistically new cleavage for enantioselective dihydroxylation reactions is introduced within the present work.

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An Electrophilic Cleavage Procedure for the Asymmetric Dihydroxylation: Direct Enantioselective Synthesis of Cyclic Boronic Esters from Olefins

Hövelmann

Muñiz

2005

Chemistry A European J

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Supramolecular Organization Based on van der Waals Forces: Syntheses and Solid State Structures of Isomeric [6.6]Cyclophanes with 2,5‐Diselenahex‐3‐yne Bridges

2009

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The ortho, meta, and para isomers 4-6 of [6.6]cyclophanes with 2,5-diselenahex-3-yne bridges were synthesized by reacting the bis(selenocyanatomethyl)benzene derivatives 8a-8c with the lithium salt of trimethylsilylethyne to yield 9a-9c, deprotection of which afforded the bis(ethynylselenylmethyl)benzenes 10a-10c. The condensation of the bis-lithium salts of 10a-10c with 8a-8c yielded the target compounds 4-6. X-ray investigations on single crystals of 4-6 revealed intermolecular Se···Se interactions which contribute significantly to the solid-state structures of these species. In the case of the orthocyclophane 4, we found short distances be-

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Intramolecular Nonbonded Interactions Between Divalent Selenium Centers with Donor and Acceptor Substituents

et al. 2009

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Keywords: van der Waals interactions / NMR spectroscopy / Selenium / Hydrogen bonds / Density functional calculationsTo investigate the intramolecular van der Waals interactions between two divalent selenium centers in the solid state and in solution, we have prepared methyl 2-(methylselenyl)benzyl selenide (1), ethynyl 2-(methylselenyl)benzyl selenide (2), and 2-(methylselenyl)benzyl selenocyanate (3). By means of NMR spectroscopic studies we have determined the 77 Se NMR chemical shifts of the signals of the Se centers of 1-3 and their long-range 4 J Se,Se coupling constants. These results, and the X-ray structural studies of single crystals of 3 and 11, a quasi-dimer of 2, point to an Se···Se van der Waals

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Sauerstoff und Osmium – ein neues Paar für Dihydroxylierungen?

Cited by 6 publications

References 20 publications

An Electrophilic Cleavage Procedure for the Asymmetric Dihydroxylation: Direct Enantioselective Synthesis of Cyclic Boronic Esters from Olefins

An Electrophilic Cleavage Procedure for the Asymmetric Dihydroxylation: Direct Enantioselective Synthesis of Cyclic Boronic Esters from Olefins

Supramolecular Organization Based on van der Waals Forces: Syntheses and Solid State Structures of Isomeric [6.6]Cyclophanes with 2,5‐Diselenahex‐3‐yne Bridges

Intramolecular Nonbonded Interactions Between Divalent Selenium Centers with Donor and Acceptor Substituents

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