Selective oxidation of cyclohexanol and 2-cyclohexen-1-ol on O/Au(111): the effect of molecular structure

We combine reactivity studies with infrared reflection absorption spectroscopy to provide molecular-scale insights into the oxidation of two cyclic alcohols, cyclohexanol and 2-cyclohexen-1-ol, by atomic oxygen adsorbed on Au(111). The two alcohols share common features in their reaction pathways: they are both activated by Br?nsted acid-base reactions with adsorbed oxygen. Cyclic ketones, cyclohexanone and 2-cyclohexen-1-one, are the major products, formed from cyclohexanol and 2-cyclohexen-1-ol, respectively. These ketones also undergo secondary ring C-H bond activation. The product distributions reflect a substantial difference in the secondary reactions for these two ketones, which correlate with their gas-phase acidity. The allylic alcohol (2-cylohexen-1-ol) has a greater degree of ring C-H activation, yielding the diketone (2-cyclohexene-1,4-dione) and phenol. Our results provide clear evidence for the importance of C═C functionalities in determining the reactivity of molecules in heterogeneous oxidative transformations promoted on Au-based materials.     

Ligand-controlled phosphine-free Co(II)-catalysed cross-coupling of secondary and primary alcohols

Cobalt(II) complexes (5 mol% Co) bearing phosphine-free N^˄N^˄N pincer ligands efficiently catalyze C–C coupling of secondary and primary alcohols to selectively form α-alkylated ketones with a good functional group compatibility using NaOH (20 mol%) as a base at 120 °C. The NH group on the N^˄N^˄N–Co(II) precatalyst controls the activity and selectivity. This simple catalytic system is involved in the synthesis of quinolones via the dehydrogenative annulation of 2-aminobenzyl alcohols with secondary alcohols.     

Mass spectra of 17ξ-hydroxy-5ξ-androstane C(3) ketone and C(3ξ) alcohol isomers

Positive ion electron impact mass spectral data for the four isomeric 17ξ-hydroxy-17ξ-methyl-5ξ-androstane C(3) ketones and the eight isomeric C(3ξ) alcohols are reported. In contrast to earlier reports, no general correlation was observed between the [M? H₂O]⁺˙/[M]⁺˙ ratio and the configuration at C(17). The ratios of the intensity of several fragment ions to that of the molecular ion do differentiate between the 5α- and 5β-isomers in both C(3) ketones and alcohols, the extent of fragmentation being greater for 5β-steroids. All of these fragments probably involve elimination of a water molecule at some stage in their formation. Elimination of water is also enhanced for 3α- v. 3β-hydroxysteroids, particularly in a 5β-isomer.     

Aerobic oxidation of alcohols using a novel combination of N-hydroxyphthalimide (NHPI) and CuBr

A new catalytic system for oxidation of alcohols with oxygen by N-hydroxyphthalimide (NHPI) combined with CuBr has been developed. The reaction results showed that this catalytic system can effectively catalyze the oxidation of alcohols to the corresponding carboxylic acids or ketones. We obtained 100% selectivity for acetophenone at 94.2% conversion of phenylethanol at 75?°C for 20?h. A mechanism of oxidation of alcohols catalyzed by NHPI/CuBr was proposed.     

Use of S-pentafluorophenyl tris(2,4,6-trimethoxyphenyl)phosphonium acetate bromide and (4-hydrazino-4-oxobutyl) [tris(2,4,6-trimethoxyphenyl)phosphonium bromide for the derivatization of alcohols,aldehydes and ketones for detection by liquid chromatography/electrospray mass spectrometry

The synthesis of S-pentafluorophenyl tris(2,4,6-trimethoxyphenyl)phosphonium acetate bromide (TMPP-AcPFP) and the novel compound (4-hydrazino-4-oxobutyl) [tris(2,4,6-trimethoxyphenyl)phosphonium bromide (TMPP-PrG) is described and the use of these compounds as derivatizing reagents for alcohols, aldehydes and ketones evaluated. Methods have been developed for the pre-column derivatization of alcohols using TMPP-AcPFP and for aldehydes and ketones using TMPP-PrG. The reactions were investigated by the use of a variety of individual test compounds containing the target functional groups. The TMPP acetyl ester and TMPP propyl hydrazone derivatives formed with their respective target analytes produced an enhanced response in electrospray ionization mass spectrometry (ESI-MS), and reproducible chromatography. The use of these two reagents to derivatize and facilitate detection of alcohols (including sugars and steroids), aldehydes and ketones (including steroids) by LC/ESI-MS was investigated.     

Asymmetric hydrogenation of alpha-primary and secondary amino ketones: efficient asymmetric syntheses of (-)-arbutamine and (-)-denopamine

Two beta-receptor agonists (-)-denopamine and (-)-arbutamine were prepared in good yields and enantioselectivities by asymmetric hydrogenation of unprotected amino ketones for the first time by using Rh catalysts bearing electron-donating phosphine ligands. A series of alpha-primary and secondary amino ketones were synthesized and hydrogenated to produce various 1,2-amino alcohols in good yields and with good enantioselectivies. This Rh electron-donating phosphine-catalyzed asymmetric hyderogenation represents one of the most promising and convenient approaches towards the asymmetric synthesis of chiral amino alcohols.     

Aminosulf(ox)ides as ligands for Iridium(I)-catalyzed asymmetric transfer hydrogenation

A new class of efficient catalysts was developed for the asymmetric transfer hydrogenation of unsymmetrical ketones. A series of chiral N,S-chelates (6-22) was synthesized to serve as ligands in the iridium(I)-catalyzed reduction of ketones. Both formic acid and 2-propanol proved to be suitable as hydrogen donors. Sulfoxidation of an (R)-cysteine-based aminosulfide provided a diastereomeric ligand family containing a chiral sulfur atom. The two chiral centers of these ligands showed a clear effect of chiral cooperativity. In addition, aminosulfides containing two asymmetric carbon atoms in the backbone were synthesized. Both the sulfoxide-containing beta-amino alcohols and the aminosulfides derived from 1,2-disubstituted amino alcohols gave rise to high reaction rates and moderate to excellent enantioselectivities in the reduction of various ketones. The enantioselective outcome of the reaction was favorably affected by selecting the most appropriate hydrogen donor. Enantioselectivities of up to 97% were reached in the reduction of aryl-alkyl ketones.     

Highly stereoselective syntheses of syn- and anti-1,2-amino alcohols

The reduction of N-protected amino ketones can be carried stereoselectively to produce either the syn- or anti-amino alcohol diastereomer. Carbamate-protected amino ketones can be reduced predictably and selectively to anti-amino alcohols with LiAlH(O-t-Bu)3 in ethanol at -78 degrees C. N-Trityl-protected amino ketones can be reduced selectively to syn-amino alcohols with LiAlH(O-t-Bu)3 in THF at -5 degrees C.     

Synthetic organic chemistry with 2-ethoxy-2-(phenylselenenyl)perfluoroalk-2-enenitrile: application to alpha-cyanoperfluoroacylation of aldehydes

(Z)- and (E)-2-Ethoxyperfluoro-2-(phenylselenenyl)alk-2-enenitriles 2-4 prepared by our original method underwent transmetalation on treatment with n-BuLi or EtMgBr, and the successive reaction with aldehyde and ketones afforded the corresponding allylic alcohols 10a-f, 9a, and 11a,b in good to high yields. Hydrolysis of the alcohols gave alpha-cyano-alpha,beta-unsaturated perfluoroalkyl ketones 13a-c, 13e, 12a, and 15a. alpha-Cyanoperfluoroalkyl ketones were easily converted to alpha,beta-unsaturated 3-aryl-2-cyanoallylic alcohols 18-22 having interesting biological activities and chemical reactivities.     

Enantioselective Catalytic Borane Reductions of Achiral Ketones: Synthesis and Application of New Rigid Catalysts Prepared from (R)-Phenylglycine and (S)-Phenylalanine

Exnantiocontrolled reduction of prochiral ketones with borane in the presence of homochiral amino alcohols 1 - 4 as enantioselective catalysts afforded the chiral corresponding secondary alcohols in moderate to high (55 to 88 %) optical yields.     

Chemical transformations of alcohols sampled with the use of adsorptive enrichment on the carbon adsorbent traps followed by thermal desorption

Graphitized carbons, Carbopack X, Carbograph 5TD and Carbotrap B, used to enrich samples of C(3)-C(4) alcohols determined in the atmospheric air produce experimental artefacts. After thermal desorption, recoveries for alcohols are much smaller than unity with a concomitant appearance of aldehydes and ketones on chromatograms. Obviously, the adsorbents studied cannot be recommended for analysis of alcohols, ketones and aldehydes in the atmosphere. Polymeric adsorbents, Tenax TA and Chromosorb 106, do not exhibit such oxidative properties.     

Synthesis of a C(1)-C(14)-containing fragment of callipeltoside A

[formula: see text] A C(1)-C(14)-containing fragment of callipeltoside A (1, Scheme 1) was synthesized efficiently via a dianion aldol coupling reaction between aldehyde 2 and ketoester 3. A surprising lack of reactivity between the alkenes in 13 and the Grubbs initiator 15 was encountered. An equally surprising rate acceleration of the reaction between 15 and allylic alcohols (alk-1-en-3-ols) as well as their subsequent cleavage to methyl ketones was discovered. In situ 1H NMR analysis has proven to be a very useful tool for monitoring RCM reactions of complex substrates such as 13.     

无溶剂条件下锰 (Ⅲ)-席夫碱配合物催化过氧化氢氧化醇

 Aliphatic and aromatic alcohols are efficiently oxidized to ketones or carboxylic acids using aqueous hydrogen peroxide as an oxidant in the presence of a Mn(III) Schiff-base complex as a catalyst under solvent-free conditions. The oxidation of alcohols occurred at 50 °C to give the corresponding ketones or carboxylic acids with a yield higher than 60%.     

Enantioselective Catalytic Borane Reductions of Achiral Ketones: Synthesis and Application Of New Catalysts Prepared from (S)-Tert-Leucine and (S)-Azetidinecarboxylic Acid

Enantiocontrolled reduction of prochiral ketones with borane in the presence of homochiral amino alcohols 1—3 as enantioselective catalysts afforded the corresponding secondary alcohols in moderate to high (69 to >99 %) optical yields.     

C‐Alkylation of Ketones and Related Compounds by Alcohols: Transition‐Metal‐Catalyzed Dehydrogenation

Transition‐metal‐catalyzed C‐alkylation of ketones and secondary alcohols, with alcohols, avoids use of organometallic or environmentally unfriendly alkylating agents by means of borrowing hydrogen (BH) or hydrogen autotransfer (HA) activation of the alcohol substrates. Water is formed as the only by‐product, thus making the BH process atom‐economical and environmentally benign. Diverse homogeneous and heterogeneous transition‐metal catalysts, ketones, and alcohols can be used for this transformation, thus rendering the BH process promising for replacing those procedures that use traditional alkylating agents. This Minireview summarizes the advances during the last five years in transition‐metal‐catalyzed BH α‐alkylation of ketones, and β‐alkylation of secondary alcohols with alcohols. A discussion on the application of the BH strategy for C?C bond formation is included.     

Chemoselective Oxidation of Benzylic Alcohols and Hydroquinones with bis-(2,4,6-Trimethylpyridinium) Dichromate (BTMPDC) as an Efficient and New Oxidizing Agent

A simple, efficient, and chemoselective oxidation of benzylic alcohols to the corresponding aldehydes and ketones and also hydroquinones to the benzoquinones using bis-(2,4,6-trimethylpyridinium) dichromate (BTMPDC) in acetonitrile is described. A good range of primary and secondary benzylic alcohols and a limited range of hydroquinones were selectively oxidized under reflux conditions in reasonable yields.     

Polystyrene‐supported Pd(II) complex‐catalysed carboacylation of 2‐arylpyridines with alcohols via C─H bond activation under solvent‐free conditions

Polystyrene‐supported N ,N ‐dimethylethylenediamine Pd(II) complex C was used as an efficient catalyst for the synthesis of aromatic ketones via ortho ‐acylation of sp² C─H bonds of 2‐arylpyridines with alcohols as effective coupling partners. The alcohols were oxidized with tert ‐butyl hydroperoxide to their corresponding aldehydes in situ and efficiently coupled with 2‐arylpyridines to form aryl ketones under solvent‐free conditions. Furthermore, catalyst C could be easily recovered by simple filtration and reused for five cycles without any significant decrease in its activity.     

Enantioselective allylation of ketones catalyzed by chiral In(III)-PYBOX complexes

In the presence of 20 mol% of chiral catalytic complex prepared from In(OTf)3 and chiral PYBOX, allyltributylstannane reacted with achiral ketones to afford the corresponding homoallylic alcohols in moderate to high enantioselectivities (54-95% ee), which constitutes the first example of enantioselective allylation of ketones catalyzed by the chiral In(III)-PYBOX complex.     

[Ru(DMSO)4]Cl2 catalyzes the α-alkylation of ketones by alcohols

The electrophilic α-alkylation of ketones with alcohols was accomplished by a [Ru(DMSO)₄]Cl₂ catalyzed process, water being the only wasted material. The reaction can be successfully governed to produce either the expected ketones or their related alcohols only by changing the reaction conditions. When 2-aminobenzyl alcohol was used, a cyclization process took place to yield 2,3-disubstituted quinolines.     

Catalytic asymmetric methallylation of ketones with an (H8-BINOLate)Ti-based catalyst

The first catalytic asymmetric methallylation of ketones is reported. The catalyst, which is generated from titanium tetraisopropoxide, H8-BINOL, 2-propanol, and tetramethallylstannane, reacts with ketones in acetonitrile to afford tertiary homoallylic alcohols in fair to excellent yields (55-99%) and fair to high enantioselectivities (46-90%). Ozonolysis of the resulting products provides access to chiral beta-hydroxy ketones, which are not readily prepared from direct asymmetric aldol reaction of acetone with ketones.