양정운 교수

The enantioselective synthesis of spirocycles has long been pursued by organic chemists. Despite their unique 3D properties and presence in several natural products, the difficulty in their enantioselective synthesis makes them underrepresented in pharmaceutical libraries. Since the first pioneering reports of the enantioselective construction of spirosilanes by Tamao et al., significant effort has been devoted towards the development of new promising asymmetric methodologies. Remarkably, with t

A highly efficient and chemo-, regio-, diastereo-, and enantioselective organocatalytic tandem conjugate reduction-Michael cyclization of enal enones has been developed. Accordingly, treating the enal enone with a Hantzsch dihydropyridine in the presence of a catalytic amount of an imidazolidinone organocatalyst provides cyclic keto aldehydes in high yields and enantiomeric excesses. The reaction works well with aliphatic and aromatic substrates in the synthesis of five- and six-membered carbacy

Impressive tolerance is displayed in the efficient and chemoselective organocatalytic transfer hydrogenation of α,β-unsaturated aldehydes in the presence of a Hantzsch dihydropyridine and a catalytic amount of dibenzylammonium trifluoroacetate (see scheme). Various sensitive functional groups such as the nitro, cyano, alkenyl, and benzyloxy groups survive these reaction conditions.

Selective reduction without metals: An imidazolidinone salt effectively catalyzes the highly enantioselective biomimetic transfer hydrogenation of α,β-unsaturated aldehydes to give the saturated analogues using a synthetic dihydropyridine cofactor (see scheme). Remarkably only one enantiomer forms regardless of the configuration of the enal starting material.

A curious cat.: The proline-catalyzed Mannich reaction between aldehydes and N-Boc-imines (Boc=tert-butoxycarbonyl) gives crystalline β-amino aldehydes with exceptionally high diastereoselectivities and enantioselectivities (see scheme). The products of this reaction typically precipitate from the reaction mixture and are useful intermediates in the synthesis of α- and β-substituted β-amino acids.

Selektive Reduktion ohne Metall: Ein Imidazolidinonsalz katalysiert effektiv die hoch enantioselektive biomimetische Transferhydrierung α,β-ungesättigter Aldehyde zu den gesättigten Analoga, bei der ein synthetischer Dihydropyridin-Cofaktor verwendet wird (siehe Schema). Dabei entsteht, unabhängig von der Konfiguration des Ausgangs-Enals, nur ein Enantiomer.

C2-symmetric chiral copper(II)-bisoxazolines function as alcohol dehydrogenase mimics and catalyze highly enantioselective transfer hydrogenations of alpha-ketoesters with Hantzsch esters as a synthetic NADH analogue to give alpha-hydroxy esters in excellent enantioselectivities. [reaction: see text].

Toleranz gefordert: Beschrieben wird die effiziente und chemoselektive Transferhydrierung von α,β-ungesättigten Aldehyden in Gegenwart von Hantzsch-Dihydropyridin und einer katalytischen Menge Dibenzylammoniumtrifluoracetat (siehe Schema). Diese organokatalytische konjugierte Reduktion toleriert reduktionsempfindliche funktionelle Gruppen wie Nitro-, Cyan-, Alkenyl- und Benzyloxygruppen.

An unprecedented high level of regioselectivities (up to 96%) in the intermolecular crossed acyloin condensations of various aromatic aldehydes with acetaldehyde was realized by an appropriate choice of N-heterocyclic carbene catalysts.

. We found that the choice of solvent was crucial for enhancing the electron transfer efficiency, and a maximum efficiency of 80% was achieved by using a DMF mixed isopropanol co-solvent system. This is the highest value reported to date among single electron transfer agents in the reduction of C-C multiple bonds. The observed reactivity and efficiency establish that electrides with a high density of anionic electrons can readily participate in the reduction of organic functional groups.

Hochselektiv: Die Prolin-katalysierte Mannich-Reaktion von Aldehyden mit N-Boc-Iminen (Boc=tert-Butoxycarbonyl) ergibt β-Aminoaldehyde mit außerordentlich hohen Diastereo- und Enantioselektivitäten (siehe Schema). Die Produkte dieser Reaktion fallen typischerweise aus der Reaktionsmischung aus und sind nützliche Zwischenstufen in der Synthese von α- und β-substituierten β-Aminosäuren.

[reaction: see text] OsO(4) was simply immobilized onto resins such as Amberlite XAD-4 or XAD-7 bearing residual vinyl groups. The resulting osmylated resins are air-stable, nonvolatile, and much easier to handle than their homogeneous counterpart (OsO(4)). Moreover, the resin-bound OsO(4) exhibited excellent catalytic activity in the asymmetric dihydroxylation of olefins and was easily recovered and reused in five consecutive reactions without any significant decrease in product yield. Turnover

The scalable pinacol coupling reaction is realized utilizing the inorganic electride [Ca2N](+)·e(-) as an electron donor in organic solvents. The bond cleavages of the [Ca2N](+) layers by methanol play a vital role in transferring anionic electrons to electrophilic aldehydes, accompanying the formation of Ca(OMe)2 and ammonia.

Advanced organic polymer electrode based on PTVE-functionalized carbon nanotubes is prepared for sodium organic battery.