The mechanism of photoinduced hydrogen transfer during photoreduction of carbonyl compounds

A model reaction of hydrogen transfer has been proposed that describes well the results of kinetic studies of the photoreduction of o- and p-quinones and fluorenone in the presence of para-substituted N,N-dimethylanilines and polyalkylbenzenes in various solvents.     

Design and synthesis of a tridentate ligand for asymmetric bifunctional catalysis

Covalent attachment of a quinine moiety to a Schiff base ligand through an ester linkage generates a novel tridentate ligand that gives a new Lewis acid-Lewis base (LA-LB^∗) bifunctional catalyst having a mixture of the LA configurations. The LB^∗-dependent asymmetric bifunctional catalysis was demonstrated using the addition of diethylzinc to 2-methoxybenzaldehyde as a test reaction and the substrate scope of the new catalyst was illustrated using aromatic aldehydes.     

Mo-Au combo catalysis for rapid 1,3-rearrangement of propargyl alcohols into alpha,beta-unsaturated carbonyl compounds

The combination of Mo and cationic Au catalysts dramatically accelerated the rearrangement of diverse propargyl alcohols, which includes a short reaction time, mild conditions, and high product yields. A practical application to the highly challenging primary propargyl alcohols and the N-alkynyl amides is achieved.     

Chiral polyamino alcohols and polyamino thiols for asymmetric heterogeneous catalysis

A series of macroporous copolymer beads were synthesized by THE free radical suspension copolymerization of (S)-glycidylmethacrylate (GMA), (S)-thiiranylmethylmethacrylate (TMA), or (R,R)-phenylglycidylmethacrylate (Ph-GMA) with ethyleneglycol dimethacrylate (EDMA) or divinylbenzene (DVB). This allowed for the evaluation of their chemical and physical properties (polymer matrix nature or the structure of the heterocyclopropane) and their influence on the catalytic efficiency. These chiral polymers were subsequently transformed into polyamino alcohol or polyamino thiol derivatives by the facile ring opening of the oxirane or thiirane group with benzylamine and methylamine. Complexed with [RuCl₂(p-cymene)]₂, these derivatives were shown to be effective in the asymmetric hydrogen transfer reduction of acetophenone. The best results (conversion: 94%, ee: 71%) were obtained with benzylamine grafted onto poly(GMA-co-EDMA) (30/70 % wt/wt).     

Synthesis of the bifunctional BINOL ligands and their applications in the asymmetric additions to carbonyl compounds

Efficient one-step syntheses of the bifunctional BINOL and H₈BINOL ligands (S)-6 and (S)-8 have been developed from the reaction of BINOL and H₈BINOL with morpholinomethanol, respectively. The X-ray analyses of these compounds have revealed their structural similarity and difference. The bifunctional H₈BINOL (S)-8 is found to be highly enantioselective for the reaction of diphenylzinc with many aliphatic and aromatic aldehydes and especially is the most enantioselective catalyst for linear aliphatic aldehydes. Unlike other catalysts developed for the diphenylzinc addition which often require the addition of a significant amount of diethylzinc with cooling (or heating) the reaction mixture in order to achieve high enantioselectivity, using (S)-8 needs no additive and gives excellent results at room temperature. (S)-8 in combination with diethylzinc and Ti(OⁱPr)₄ can catalyze the highly enantioselective phenylacetylene addition to aromatic aldehydes. It can also promote the phenylacetylene addition to acetophenone at room temperature though the enantioselectivity is not very high yet. Without using Ti(OⁱPr)₄ and a Lewis base additive, (S)-8 in combination with diethylzinc can catalyze the reaction of methyl propiolate with an aldehyde to form the highly functional γ-hydroxy-α,β-acetylenic esters except that the enantioselectivity is low at this stage. The bifunctional BINOL ligand (S)-6 in combination with Me₂AlCl is found to be a highly enantioselective catalyst for the addition of TMSCN to both aromatic and aliphatic aldehydes.     

Reduction of carbonyl compounds via hydrosilylation: V. Synthesis of optically active allylic alcohols via regioselective asymmetric hydrosilylation

Regioselective asymmetric reduction of prochiral α,β-unsaturated ketones to optically active allylic alcohols was performed via hydrosilylation catalyzed by a rhodium(I) complex with (+)-BMPP, (+)-DIOP and (?)-DIOP as chiral ligands. The allylic alcohols with optical purity up to 69% e.e. were obtained in good yields. The extent of asymmetric induction was found to depend on the stereo-electronic matching of the chiral ligand, ketone and hydrosilane employed. In the asymmetric reduction of (R)-carvone, leading to carveol, the extent of asymmetric induction was found to depend markedly on the ligand/rhodium ratio. Either trans-(5R,1S)-carveol or cis-(5R,1R)-carveol was obtained with good stereoselectivity by using (?)-DIOP or (+)-DIOP as chiral ligand, and it turned out that the chiral center present in carvone had only a slight influence on the asymmetric induction by the chiral catalysts.     

BINOLAM,a recoverable chiral ligand for bifunctional enantioselective catalysis: the asymmetric synthesis of cyanohydrins

[reaction: see text] A new bifunctional catalytic system based on a monometallic aluminum complex is used for the efficient enantioselective cyanation of aldehydes. The ligand (S)- or (R)-2,2'-bis(diethylaminomethyl)-substituted binaphthol (BINOLAM) used is recovered for recycling. This methodology is used for the synthesis of a precursor of epothilone A.     

An efficient and sustainable protocol for oxidation of alcohols to carbonyl compounds

A simple and extremely efficient protocol is developed for oxidation of alcohols to carbonyl compounds at room temperature by using green solvent lactic acid and green oxidant H₂O₂. This protocol provides high conversion under catalyst free conditions. The easy work up procedure allows high selectivity and good to excellent yields of carbonyl compounds with purity. We have performed wide range of substrates in present study with primary focus on reusability of lactic acid.     

Zinc-mediated alkynylation of carbonyl compounds with iodoalkynes: a facile synthesis of propargyl alcohols

A straightforward synthesis of propargyl alcohols from alkynyl iodides and carbonyl compounds using zinc is described.     

Polymer bromide-DMSO: novel reagent system for the oxidation of alcohols to carbonyl compounds

A novel method for the oxidation of alcohols to aldehydes is described using polymer bromide-DMSO at room temperature. The condition described enables clean and fast conversion to desired carbonyl compounds and a broad range of substrates are tolerated. The resin recovery and recyclability make the protocol more ecofriendly.     

Use of odorless thiols: formal asymmetric Michael addition of hydrogen sulfide to alpha-substituted alpha,beta-unsaturated carbonyl compounds

[reaction: see text] The Michael addition to alpha-substituted alpha,beta-unsaturated esters and amides using complex A containing a chiral odorless thiol proceeded diastereoselectively. The Michael adducts were converted to beta-mercapto esters and amides via a Wagner-Meerwein rearrangement with boron trifluoride etherate and a thiol exchange reaction using odorless 1-dodecanethiol. This conversion constitutes a formal asymmetric Michael addition of hydrogen sulfide to alpha,beta-unsaturated carbonyl compounds using odorless thiols instead of the toxic hydrogen sulfide.     

Aqueous electrosynthesis of carbonyl compounds and the corresponding homoallylic alcohols in a divided cell

An aqueous paired electrosynthesis is studied in a divided cell. On graphite anode Br⁻ was oxidized to Br₂ and this generated Br₂ oxidized alcohols to the corresponding carbonyl compounds while Sn²⁺ was reduced to Sn⁰ on graphite cathode. Then the produced metallic tin mediated allylation of the carbonyl compounds with allyl bromide to generate the corresponding homoallylic alcohols. In the reaction the mediators (Sn and Br₂) were generated in situ and could be reused via the electrolysis. Both working electrode and the counter electrode were utilized to generate useful products without the sacrifice of the electrode materials.     

Mechanism of the hydroamination of alcohols and carbonyl compounds on a fused iron catalyst

In a study of the reaction of 2,2-dimethyl-1-propanol, 2-ethyl-1-hexanol, 2-octanol, and 4-heptanol or 4-heptanone and 2-octanone with aminating agents such as ammonia, dimethylamine, and propylamine in the presence of hydrogen on a fused iron catalyst, we showed that the desired amines are formed through both imine and enamine mechanisms.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1923–1926, August, 1990.