Visible light photoredox-catalyzed deoxygenation of alcohols

• Daniel Rackl,
• Viktor Kais,
• Peter Kreitmeier and
• Oliver Reiser

Beilstein J. Org. Chem. 2014, 10, 2157–2165, doi:10.3762/bjoc.10.223

• ; dtb-bpy = 4,4′-di-tert-butyl-2,2′-bipyridine] as photocatalysts, Hantzsch ester (diethyl 1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate) as hydrogen donor, and iPr2NEt as sacrificial electron donor in DMF (Scheme 3). Light generated from a high power LED was channeled into the reaction solution in

• ) was omitted significantly lower yields were obtained. Leaving out Hantzsch ester (Table 2, entry 8) apparently does not impede the deoxygenation while carrying out the reaction without Hünig’s base lowers the yield (Table 2, entry 9), nevertheless, 4 was still formed to a significant extent. These

• results suggest that Hantzsch ester is not necessary as the hydrogen source but likewise that reductive quenching of the photocatalyst is not exclusively accomplished by Hünig’s base. We assumed that the mechanism of the deoxygenation reaction involves an electron uptake of the ester moiety from the

Synthesis of chiral N-phosphinyl α-imino esters and their application in asymmetric synthesis of α-amino esters by reduction

• Yiwen Xiong,
• Haibo Mei,
• Lingmin Wu,
• Jianlin Han,
• Yi Pan and
• Guigen Li

Beilstein J. Org. Chem. 2014, 10, 653–659, doi:10.3762/bjoc.10.57

• used for the asymmetric synthesis of α-amino esters through reduction. The reduction condition scan was firstly focused on the examination of reductants. A number of reductants, including Hantzsch ester, silanes, organoaluminum and boranes were tested in the system. Unfortunately, silanes failed to

• trigger the reduction (Table 3, entries 2 and 3). Hantzsch ester and DIBAL were also not suitable for this reduction, and almost no desired product was obtained (Table 3, entries 1 and 5). Lithium triethylborohydride (Table 3, entry 4) and sodium borohydride (Table 3, entry 6) were decent choices, giving

Enantioselective reduction of ketoimines promoted by easily available (S)-proline derivatives

• Martina Bonsignore,
• Maurizio Benaglia,
• Laura Raimondi,
• Manuel Orlandi and
• Giuseppe Celentano

Beilstein J. Org. Chem. 2013, 9, 633–640, doi:10.3762/bjoc.9.71

• donor functionality as the carboxylic acid group; it is worth mentioning that also phosphoric acid catalyzed reductions of C=N bonds with Hantzsch ester involve the coordination and activation of the substrate through the formation of a H-bond between the hydrogen atom of the phosphoric acid and the

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• ]. Photocatalysis can also be performed by using visible light. This has been applied to the hydrodehalogenation of α-haloketones by using the dye Eosin Y (36) as a photocatalyst, and both DIPEA and Hantzsch ester 35 as electron donors (Scheme 13). The reaction was shown to be high yielding for a number of

Combining two-directional synthesis and tandem reactions, part 11: second generation syntheses of (±)-hippodamine and (±)-epi-hippodamine

• Annabella F. Newton,
• Martin Rejzek,
• Marie-Lyne Alcaraz and
• Robert A. Stockman

Beilstein J. Org. Chem. 2008, 4, No. 4, doi:10.1186/1860-5397-4-4

• sodium borohydride, sodium cyanoborohydride and Hantzsch ester in either ethanol or ethanol / acetic acid solvent systems. A summary of conditions tried is shown in Table 1. The ketodiester 9 was dissolved in ethanol and the ammonia source and desiccant were added and allowed to stir overnight to form

• entry 6 showed reduction of the ketone to the alcohol (by 1H NMR), and entry 5 using the Hantzsch ester showed no reaction at all. It was found that addition of ammonia in ethanol with titanium ethoxide [15] for 14 hours, followed by addition of sodium borohydride and stirring at room temperature for a