Chemischen Institut der Universität Jena: Methode zum Ersatz des Sauerstoffatoms der Ketone und Aldehyde durch Wasserstoff. [Erste Abhandlung.]

Abstract

Yo I f f , Methode zum Ersatz des Sauerstoffaloms usiu. $7Die Hydrazone blieben entweder unverandert. oder es trat Szinbildung ein: die Semicarhazone gingen in die Hydrazone iiber. DaS die Hydrazone sich beim Erhitzen in die h i n e umwandeln, hat C u r t i u s schon ;d.ngegebcn.Beziiglich der Bestandigkeit der Hydrazone machen sich groDe Unterschiede geltend. Einzelne sind recht haltbar und leicht zu isolieren, andere, wie Canipherhydrazon, zersetzen sich schon bei gewohnliclier Temperatur in die Azine, wobei das Wasser eine Rolle spielt, entprecliend folgenden Gleichnngen:M, >C=S.SII, + oc< = >c=s.s=c< + IJ,O. Die Nrkenntnis, daS die Gegeiiwart selbst kleiner RIengen Kassers die Azinbildung fordert nnd wohl auch einleitet, hat dazu gefiitirt, die Umsetzung der Hydrazone bei vollstLndigem AbschlnS von U-assclr mittelst ahsolut alkolioli.wher Nah-iiirniitli~ZatlIsusg vorzunehmen. Das Resnl-&i t war iiberraschcnd giinstig. Xzinbildung fand dabei Uberlianpt niclit, oder in untergeordnetem MaBe statt, und die Abspaltung des Sticlistoffs eifolgte gane glatt. duch bei Verwendung von Natriumiitliylat entstehen aus den Semicarbayonen, wenn die Temperatur nicht hoch genng genommen wird, als Zwischenprodukte die Hydrazone, die bei hiilierer Teniperatur in die Rohlenwasser-stof€e iibergehen; der Reaktionsverlanf ist also folgender: \C=S.SH.CONH, $-H,O = )C=N.MI, + (YO, + NH, \c=s.r;rr, = >cs, + 2s. / / Die ,\lethodc hat bisher bei Hydrazonen und Seraicarbazonen nicniels versagt und ist, wie sicli aus dcm experimentellen Teil ergibt, allgemcin uerwendbnr lrei al+liati.\chen und aromntischm, ziberhaupt cyclischen Ketonen wid Adehyden, ferner bei Ketomiiuren. Die Reduktionsyrodukte entstehen in recht guter Ausbeute (75-90 Proz. der Theorie) und sind meist leicht in reinem Zustand zu

Chromophores from hexeneuronic acids: identification of HexA-derived chromophores

“…The chromophores evidently represent a special case here where yields are unusually high. Interestingly, also reduction under alkaline conditions, for instance the standard Wolff-Kishner reduction (Szmant 1968;Wolff 1912), carried out with solid KOH and hydrazine in diethylene glycol, proceeds neatly with similarly high yields. It is rather unusual that a ketone can be reduced well to the alkane under both acidic and alkaline conditions; normally a clear preference Scheme 9 Proposed mechanism of the formation of chromophore 6 from ''core chromophore'' 4, involving a DielsAlder reaction with diene 2 as the key step.…”

Catalytic Ketone Hydrodeoxygenation Mediated by Highly Electrophilic Phosphonium Cations

“…[11] Classic protocols for deoxygenation include the Barton-McCombie (R 3 SnH), [12] Clemmensen (Zn/Hg,H Cl), [13] or Wolff-Kishner reductions (H 4 N 2 , KOH), [14] and these methods generally require harsh reaction conditions,use stoichiometric amounts of toxic reagents,and show poor functional-group tolerance.H eterogeneous catalysis employing,f or example,P tO 2 [15] and Ni/Al 2 O 3 [16] and H 2 as the reducing agent is known, while ar ecent report has described the use of Pd/C [17] with polymethylhydrosiloxane (PMHS) for the reduction of aromatic ketones. [11] Classic protocols for deoxygenation include the Barton-McCombie (R 3 SnH), [12] Clemmensen (Zn/Hg,H Cl), [13] or Wolff-Kishner reductions (H 4 N 2 , KOH), [14] and these methods generally require harsh reaction conditions,use stoichiometric amounts of toxic reagents,and show poor functional-group tolerance.H eterogeneous catalysis employing,f or example,P tO 2 [15] and Ni/Al 2 O 3 [16] and H 2 as the reducing agent is known, while ar ecent report has described the use of Pd/C [17] with polymethylhydrosiloxane (PMHS) for the reduction of aromatic ketones.…”

“…Hydrodeoxygenation of ketones has garnered increasing attention given its many applications in biofuels and finechemical syntheses. [11] Classic protocols for deoxygenation include the Barton-McCombie (R 3 SnH), [12] Clemmensen (Zn/Hg,H Cl), [13] or Wolff-Kishner reductions (H 4 N 2 , KOH), [14] and these methods generally require harsh reaction conditions,use stoichiometric amounts of toxic reagents,and show poor functional-group tolerance.H eterogeneous catalysis employing,f or example,P tO 2 [15] and Ni/Al 2 O 3 [16] and H 2 as the reducing agent is known, while ar ecent report has described the use of Pd/C [17] with polymethylhydrosiloxane (PMHS) for the reduction of aromatic ketones.…”

Direct Reductive Deoxygenation of Aryl Ketones Catalyzed by Oxo‐Rhenium Complexes

“…The decarbonylation of ketones is also a very important reaction for the deoxygenation of compounds derived from biomass. [2,3] Generally, the reduction of a carbonyl group to the corresponding methylene derivative can be carried out by chemical methods such as the Clemmensen reduction, [4] the Wolff-Kishner reduction, [5] with NaBH 4 -CF 3 CO 2 H, [6] HI-phosphorus, [7] TMSCl-Zn, [8] GaCl 3 -Me 2 SiClH, [9] InCl 3 -TMSCl, [10] PMHS-Pd(OAc) 2 (PMHS = polymethylhydrosiloxane), [11] PMHS-B(C 6 F 5 ) 3 , [12] InBr 3 -Et 3 SiH, [13] and with Raney nickel-2-propanol. [14] This reaction can also be performed by catalytic hydrogenation by using Pd-choline-based ionic liquids, [15] Cu/SiO 2 , [16] or Cu 30 Cr 10 /gAl 2 O 3 .…”