Zinc acetate complexes with ac hiral diphenylethylenediamine (DPEDA)-derived ligand have been proved to be efficient catalysts for the enantioselective hydrosilylation of aryl ketones.R eplacing pyrophoric dialkylzinc with the readily available zinc salt simplifies the procedures and provides excellent conversions (up to > 99%) and enantioselectivities(eesupt o9 7%).Keywords: asymmetric synthesis;c hiral alcohols; hydrosilylation;reduction;zinc Asymmetric hydrosilylation of prochiral ketones followed by hydrolysis of the resulting silylether is avaluable tool for the synthesis of enantiopure secondary alcohols,w hich are important building blocks in pharmaceutical, agrochemical, fragrance and flavoring chemistry.[1] Reductiono fk etones,i ncluding asymmetrich ydrosilylation, was commonly carriedo ut using platinum-group metals such as Ru, Rh or Ir. [2] Recently,e nvironmentally benign and less expensive catalysts have also been exhaustively exploredl eading to broad acceptance of earth-abundant metals such as zinc [3] and iron [4] in asymmetric synthesis. Particularly stimulating progress has been observed recently in the asymmetric hydrosilylation of ketones promoted by ironc omplexes.S ince Nishiyama [5] and Beller [6] reported the first examples of Fe(OAc) 2 -catalyzed asymmetric hydrosilylation with (EtO) 2 MeSiH and (EtO) 3 SiH, manyi ron-based catalysts have been studied for the asymmetric hydrosilylation of ketones.[7] However, ironc omplexes are often sensitive to the reactionc onditions due to the easy oxidation of iron(II)a nd also require relatively elevatedt emperatures. Only recently, an example of am ore reactive and enantioselective iron complex with the boxmi ligand has been presented by Gade. [8] In contrast to iron, zinc has only one oxidation state anda sarelatively more stable elements hould deserve certain attention. Surprisingly,s uccessfula pplications of Zn catalysts for asymmetric hydrosilylation are mostly limited to diethylzinc. Theprotocolinvolving application of Et 2 Zn with chiral ligands for the enantioselective reductiono fc arbonyl compounds with PMHS was developed by Mimouni nt he late 1990s.[9] Theb est results for the asymmetric hydrosilylation of acetophenonew ere achieved when diamine ligands were used (eesu pt o8 8%).[10] Zinc complexes with various chiral diamine scaffolds were furtheri nvestigated by Walsh, [11] Carpentier [12] andM ikami [13] providing chiral alcohols with good enantioselectivities (up to 85% ee). Va riationso fc hiral diaminocyclohexane (DACH)-based ligands have been also demonstrated [14] including an interesting applicationo f am acrocyclic oligoamine for asymmetric reduction with eesu pt o8 9%. [15] In contrast to well-developed applicationo fdiethylzinc with various ligands,h ydrosililation promoted by inorganic Zn salts is stilli ni ts infancy.I n2 009, Nishiyama developed more sustainable catalysts for asymmetrich ydrosilylation by replacing the highly reactive and hazardous dialkylzinc with zinca cetate.[16] Ligandsb earing thiophene ri...

Heterocycles are important class of structures, which occupy a major space in the domain of natural and bioactive compounds. For this reason, development of new synthetic strategies for their controllable synthesis became of special interests. The development of novel photoredox systems with wide-range application in organic synthesis is particularly interesting. Organic dyes have been widely applied as photoredox catalysts in organic synthesis. Their low costs compared to the typical photocatalysts based on transition metals make them an excellent alternative. This review describes proceedings since 2015 in the area of application of metal-free, visible-light-mediated catalysis for assembling various heterocyclic scaffolds containing five- and six-membered rings bearing nitrogen and oxygen heteroatoms.

A visible-light-mediated process for dehydrogenation of amines has been described. The given protocol showed a broad substrate scope, mild reaction conditions and excellent results without the requirement of tedious purification.

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The visible‐light‐mediated oxygenation of 3‐N,N‐(dimethylaminomethyl)‐indoles bearing various substituents afforded a series of 3‐carbaindole derivatives. Herein we describe the reaction scope, a plausible mechanism and a practical application of this transformation in the formal synthesis of (–)‐vincorine is described as well.

Herein, we describe the first, fully organocatalytic Tsuji–Trost‐type direct α‐allylation of α‐branched aldehydes by the combined use of N‐triflyl amides and secondary amines. Aliphatic, aromatic aldehydes as well as allyl alcohols are converted into the corresponding α‐allylated products in moderate to high yields.

Zinc Acetate-Catalyzed Enantioselective Hydrosilylation of Ketones. -The enantioselective hydrosilylation of a broad range of aryl ketones succeeds using a stable and inexpensive zinc salt together with easily accessible chiral diamine ligands. The reduction works for aliphatic ketones too but the products are racemic. Heterocyclic ketones such as 3-furanyl or 3-pyridyl methyl ketone do not react under given conditions even at doubled reaction times (not shown). -(SZEWCZYK, M.; STANEK, F.; BEZLADA, A.; MLYNARSKI*, J.; Adv. Synth. Catal. 357 (2015) 16-17, 3727-3731, http://dx.doi.org/10.1002/adsc.201500583 ; Fac. Chem., Jagiellonian Univ., PL-30-060 Krakow, Pol.; Eng.) -H. Haber

A facile protocol for the dehydrative cyclization of 1,3‐diaryl diketones to give functionalized flavones is developed.