Employing the simple monosilylcopper reagent,Li[PhMe2SiCuI], in 1,4-addition reactions

Conjugate addition reactions using the simple Li[PhMe2SiCuI] reagent to a variety of alpha,beta-unsaturated carbonyl compounds is described; dimethyl sulfide from the purification of CuI plays a key role for very high yields as well as high stereoselectivities in the formation of beta-silyl carbonyl compounds.     

Iron(III)picolinate-induced oxygenation and subsequent rearrangement of triterpenoid derivatives with hydrogen peroxide

The reaction of oleanane triterpenoid 1b with a FeIII(PA; picolinate)3/H2O2/MeCN system (reagent system A), a simple model system for mono-oxygenase, gave the 11 alpha-hydroxyl derivative 3 as major product, along with 11-oxo derivative 4 and 12-oxo derivative 6. The reaction of lupane triterpenoid 2b with reagent system A gave only oxidative rearrangement compounds, (20R)-aldehyde 8 and (20S)-aldehyde 9 were epimeric isomers. Then, we have found that iron(III) picolinate complex, FeIII(PA)3 is efficient in effecting the rearrangement of triterpenoid epoxides 5 and 7 into the corresponding carbonyl compounds, 6, 8 and 9 with 1,2-shift of the hydride.     

Preparation and application of odorless 1,3-propanedithiol reagents

2-Dodecyl-1,3-propanedithiol (2a) was prepared without a malodorous procedure as an odorless reagent that was usable in place of 1,3-propanedithiol (1) in organic reactions, e.g., in the reduction of azides and protection of carbonyl groups. The 1,3-dithioacetals obtained in the latter reaction were effectively reduced to methylene with Raney nickel and reconverted to the original carbonyl compounds by hydrolysis with N-bromosuccinimide in aqueous 2-butanone. In addition, the anion of 1,3-dithiane prepared from 2a and formaldehyde could be utilized as a synthetic equivalent of an anionic carbonyl carbon.     

Conjugate additions of a simple monosilylcopper reagent with use of the CuI.DMS complex: stereoselectivities and a dramatic impact by DMS

Conjugate additions utilizing the simple monosilylcuprate reagent Li[PhMe2SiCuI] to alpha,beta-unsaturated carbonyl compounds are described. The presence of dimethyl sulfide (DMS), either as a component originating from the (CuI)4(DMS)3 complex or as a solvent added, has an amazing influence on both chemical yield and the level of diastereomeric ratio (dr) of the products. Gilman-type silylcyanocuprates {Li(Ph2MeSi)2Cu/LiCN} have previously been used to guarantee good results in conjugate addition reactions. External additives such as HMPA, tributylphosphine, or dialkylzinc are not necessary in conjunction with the simple Li[PhMe2SiCuI] reagent. It is demonstrated that the monosilylcuprate reagent with DMS as the solvent is very useful with sterically hindered (beta,beta-disubstituted) enones, and provides very high yields of the beta-silylated 1,4-addition products. Since there is no oligomerization problem associated with the simple monosilylcuprate reagent, this reagent should be considered as a very useful 1,4-silyl donor to enals, enones, and enoates in conjugate addition reactions.     

Preparation of poly(vinylbenzyltriphenylphosphonium perbromide) and its application in the bromination of organic compounds

Insoluble poly(vinylbenzyltriphenylphosphonium perbromide) was prepared by the chemical modification of 2% crosslinked poly(p-bromomethylstyrene) with triphenylphosphine followed by treatment of the obtained polymeric salt with bromine. The activity of the resulting polymeric brominating reagent was compared with that of the low molecular weight model reagent in the direct brominations of alkenes and carbonyl compounds. In addition to the excellent yields of the brominated products and the ease and simplicity of the method, the resulting polymeric by-product could be simply regenerated to give the reagent without loss of activity.     

Analysis of aldehydes and ketones from beer as O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine derivatives

O-(2,3,4,5,6-pentafluorobenzyl)Hydroxylamine (PFBOA) was used as a derivatization reagent for carbonyl compounds in beer. Derivatization was carried out in aqueous solution without extraction or concentration of the sample. The effects of antifoam agent, reaction time and pH on the reaction efficiency were studied. Antifoam RD, a silicone polymer-based antifoam reagent, was the best antifoaming agent since it did not cause interferences. Reaction time studies showed that the yield of aldehydes increased up to 12 hr and then decreased slightly. The yield of 3-hydroxybutanone, a test compound for ketones, increased throughout the 48 hr test period. The natural pH of beer (ca. 4.5) was favourable for the determination of carbonyl compounds as PFBOA derivatives. Higher pH values caused yield losses and some compounds, such as butanedione, 2,3-pentanedione and 5-hydroxymethyl-2-furfural, could not be measured at all in neutral or basic conditions. Carbonyl compounds were identified by GC-MS, using three different ionization techniques, electron impact ionization, chemical ionization, and negative chemical ionization. The formation of the protonated molecules by ammonia chemical ionization and formation of the negative molecular ions and [M - HF](-.) ions by negative chemical ionization permitted reliable identification of the various carbonyl compounds studied. Sixteen carbonyl compounds from the 32 standard compounds were identified in beer and 11 of the most significant were quantitated using GC-ECD. Reproducibility of quantitation for beer samples was good, the relative standard deviations varied between 2.7 and 6.7 %. The estimated detection limits of the PFBOA derivatives of the carbonyl compounds in beer varied in the range of 0.01-1 microg/dm(3).     

Dilithiation of 1-benzenesulfonylindoles

Benzenesulfonylindole is converted to a dilithio derivative by 2.2 equivalents of lithiating reagent. The dilithio derivative gives rise to sultones on reaction with carbonyl compounds. This reaction proceeds by an intramolecular displacement of the indole group from the bis-adduct. Fair to poor yields of the 2-indolycarbinols can also be isolated. Benzoyl chloride forms a thiazine dioxide ring by addition at both the 2-indolyl and 2′-phenylsulfonyl positions. 3-Methyl-1-benzenesulfonylindole is also easily dilithiated.     

A Facile Ester Homologation of Carbonyl Compounds Via Ketene-O,S-Acetals

A usefull extension of the available methods for the conversion of carbonyl compounds into ketene-O,S-acetals^1,2,3 has been found in the Peterson olefination with methoxyphenylthiotrimethylsilyl-methyllithium 1 of aldehydes and ketones. The starting material for this reagent 1 was prepared by reaction of methoxyphenylthio-methyllithium^4,5 with chlorotrimethylsilane at -80°C in THF. Deprotonation of the obtained methoxyphenylthiotrimethylsilyl-methane with n-butyllithium at -80°C in THF gave 1 and subsequent addition of the carbonyl compound at -80°C gave mixtures of Z and E ketene-O,S-acetals 2.     

Selective indium-mediated 1,2,4-pentatrien-3-ylation of carbonyl compounds for the efficient synthesis of vinyl allenols

A highly selective synthetic method of functionalized vinyl allenols was developed from the reactions of various carbonyl compounds with organoindium reagent in situ generated from indium and 1-bromopent-4-en-2-yne derivatives. Treatment of vinyl allenols with gold catalyst, dienophile, or indium trihalide produced the functionalized dihydrofuran, cyclohexene, or 2-halo-1,3-diene derivatives in good to excellent yields.     

Catalytic oxidations of alcohols to carbonyl compounds by oxygen under solvent-free and transition-metal-free conditions

A green catalytic oxidation of alcohols to carbonyl compounds by oxygen was developed by using catalytic amounts of [bis(acetoxy)iodo]benzene/TEMPO/KNO₂. In addition, the use of a catalytic amount of poly[4-(bis(acetoxy)iodo)]styrene led to yields (up to 99%) comparable to the non-supported hypervalent iodine reagent, while offering the advantage of an efficient recovery and the subsequent recycling of the hypervalent iodine reagent.     

Application of a data-processing model to determine the optimal sampling conditions for liquid phase trapping of atmospheric carbonyl compounds

The reactivity of two fluorescent derivatization reagents, 2-diphenyl-1,3-indandione-1-hydrazone (DIH) and 2-aminooxy-N-[3-(5-dimethylamino-naphtalene-1-sulfonamino)-propyl]-acetamide (dansylacetamidooxyamine, DNSAOA), was studied towards selected atmospheric carbonyl compounds. The results were compared to those obtained using the 2,4-dinitrophenylhydrazine (2,4-DNPH) UV–vis reagent, a standard well-established technique used to detect atmospheric carbonyl compounds. The experimental rate constant were integrated into a data-processing model developed in the laboratory to simulate the trapping efficiencies of a mist chamber device as a function of temperature, reagent and solvent type among others. The results showed that in an aqueous solution, DNSAOA exhibits a higher reactivity towards carbonyl compounds without the addition of an acidic catalyst than 2,4-DNPH. It was observed that DNSAOA can trap efficiently water-soluble gaseous compounds (for example formaldehyde). However, because of a high initial contamination of the reagent caused by the synthesis procedure used in this work, DNSAOA cannot be used in high concentrations. As a result, very low trapping efficiencies of less reactive water-insoluble gaseous compounds (acetone) using DNSAOA are observed. However, the use of an organic solvent such as acetonitrile improved the trapping efficiencies of the carbonyl compounds. In this case, using DIH as the derivatization reagent (DNSAOA is not soluble in acetonitrile), trapping efficiencies greater than 95% were obtained, similar to 2,4-DNPH. Moreover, fluorescence associated with DIH derivatives (detection limits 3.33 × 10⁻⁸ M and 1.72 × 10⁻⁸ M for formaldehyde and acetone, respectively) is further advantage of this method for the determination of carbonyl compounds in complex matrix compared to the classical UV–vis detection method (detection limits 3.20 × 10⁻⁸ M and 2.9 × 10⁻⁸ M for formaldehyde and acetone, respectively).     

Efficient hydrosilylation of carbonyl compounds by 1,1,3,3-tetramethyldisiloxane catalyzed by Au/TiO2

1,1,3,3-Tetramethyldisiloxane (TMDS) is a highly reactive reducing reagent in the Au/TiO₂-catalyzed hydrosilylation of carbonyl compounds relative to monohydrosilanes. The reduction of aldehydes or ketones with TMDS can be performed on many occasions at ambient conditions within short reaction times and at low loading levels of gold, whereas typical monohydrosilanes require excess heating and prolonged time for completion. The product yields are excellent, while almost stoichiometric amounts of carbonyl compounds and TMDS can be used. It is postulated that the enhanced reactivity of TMDS is attributed to the formation of a gold dihydride intermediate. This intermediate is also supported by the fact that double hydrosilylation of carbonyl compounds by TMDS is a negligible pathway.     

Fe-Mediated S–S Bond Cleavage and Its Application in the Synthesis of α-Arylthio Carbonyl Compounds

In the presence of iron dust, diaryl disulfides react with α-bromo carbonyl compounds to obtain α-arylthio carbonyl compounds in good yield at 90 °C under an N₂ atmosphere, using commercial dimethylformamide (DMF) as solvent. The possible reaction mechanism is that the disulfide is reduced by iron dust to give ArSFeSAr and then reacted with α-bromo carbonyl compounds to give product α-arylthio carbonyl compounds and FeBr₂.     

单取代芳烃对位选择性碳氢活化反应研究

以单取代芳烃为芳基化试剂,以羰基为导向定位基团,研究了单取代芳烃对位选择性与芳香酮的交叉脱氢偶联反应。该方法的高选择性一方面体现在用作芳基化试剂的单取代芳烃能够单一选择性地发生对位碳氢活化,并生成对位取代产物;另一方面,作为弱导向基团的羰基具有优异的邻位导向定位作用,高选择性地发生羰基邻位碳氢键活化。此外,该方法还具有反应条件温和、反应效率高、底物范围广、氧化剂廉价易得等优点,为对位取代联芳基化合物的合成提供了一条切实可行的途径。     

Regioselectivity in the addition of vinylmagnesium bromide to heteroarylic ketones: C- versus O-alkylation

The reactivity of heteroarylic ketones toward vinylmagnesium bromide (2) and the regiochemistry of the addition were investigated. The reactivity drastically increases when the carbonyl is conjugated with at least one aza group and the regiochemistry of the addition of the vinyl Grignard reagent depends on the carbonyl compound: in the series of di(heteroazolyl) ketones the O-alkylation product was observed as unique with di(1,3-benzothiazol-2-yl) ketone, and in different relative ratios with respect to the classic C-alkylation product with di(1,3-thiazol-2-yl) ketone, (1,3-benzothiazol-2-yl) (1,3-thiazol-2-yl) ketone, and di(1,3-benzoxazol-2-yl) ketone, whereas di(N-methylbenzimidazol-2-yl) ketone gave the exclusive formation of the carbinol. This behavior can be explained by the intervention of the delocalization power of the heterocyclic ring and this was confirmed by the results obtained from the reaction between vinylmagnesium bromide and a series of mixed (1,3-benzothiazol-2-yl) (para-substituted phenyl) ketones, that showed a relative O-/C-alkylation ratio dependent on the nature and on the electronic effect of the substituent on the phenyl ring. The results are in agreement with the existence of intermediate species bearing a negative charge on the benzylic carbonyl carbon atom, and make the O-alkylation reaction between vinyl Grignard reagents and carbonyl compounds no longer a rare case, since it was observed with a number of heterocyclic carbonyl compounds, such as (1,3-benzothiazol-2-yl) aryl ketones and di(heteroaryl) ketones of the pentatomic 1,3-heteroazolic series.     

Rongalite and base-promoted cleavage of disulfides and subsequent Michael addition to α,β-unsaturated ketones/esters: an odorless synthesis of β-sulfido carbonyl compounds

A highly practical method to access β-sulfido carbonyl compounds was developed, which could be conducted without any expensive reagent, special apparatus/technique, and no requirement of metal catalysts. β-Sulfido carbonyl compounds were formed at room temperature, in short time and with high chemoselectivity in good to excellent yields. A plausible mechanism for the role of Rongalite^®, as a promoter for the cleavage of disulfides generating thiolate anions that then undergo facile thia-Michael addition to α,β-unsaturated ketones and esters is proposed.     

Synthesis of aryl(ferrocenyl)methanols via an enantioselective addition of arylboronic acids

Enantiomerically enriched ferrocenyl alcohols are important intermediates in the synthesis of a range of chiral ferrocene-derived ligands. We studied various possibilities for their synthesis by the catalytic enantioselective addition of arylboronic acids to ferrocenyl carbonyl compounds. The best system comprised of ferrocenyl oxazolinyl alcohol as a catalyst and an arylation reagent generated from a boronic acid and diethylzinc. Aryl ferrocenyl methanols were synthesized in yields of up to 97% and with enantiomeric purities of up to er 98:2.     

Remarkable enhancement of photo-allylation of aromatic carbonyl compounds with a hypervalent allylsilicon reagent by donor molecules

Photo-allylation of various aromatic carbonyl compounds with a penta-coordinated allylsiliconate reagent was remarkably accelerated by the addition of a donor molecule. As the oxidation potential of the allylsiliconate was significantly decreased in the presence of a donor molecule, the more efficient photo-induced electron transfer from the allylsiliconate to the excited substrate was enabled by the hexa-coordination of the silicon atom.     

Synthesis and olefination of carbonyl compounds using solid-supported reagents

The development and application of three new solid-supported reagents for use in the synthesis or olefination of carbonyl compounds are described. The reagents include the Weinreb amide, Mukaiyama's S-2-pyridyl thioate and a Peterson methylenation reagent. As solid-supports p-benzyl alcohol resin, Wang resin and Merrifield resin (1-2% crosslinked polystyrene) have been used.     

α－羰基烯酮环二硫代缩醛化学（Ⅺ）──α－羰基烯酮环二硫代缩醛类化合物与Reformatsky试剂的加成反应初步研究

报道了标题化合物和Ｒｅｆｏｒｍａｔｓｋｙ试剂［Ｅｔｈｙｌ（ｂｒｏｍｏｚｉｎｃｉｏ）ａｃｅｔａｔｅ］的加成反应。实验表明，该加成反应能否进行和α－羰基烯酮二硫代缩醛类化合物中缩醛基结构密切相关．结合晶体结构数据和构象分析可以推测，当缩醛基的两个烷硫基处在（或近于）同一平面上时，因满足了两个硫原子和Ｒｅｆｏｒｍａｔｓｋｙ试剂形成络合物的电子要求，底物被活化而易发生加成反应；反之，两个烷硫基难于处在同一平面上时，加成反应难以进行。