Reactions of 2,3-diferrocenylcyclopropenone with methyllithium and phenyllithium

Reactions of 2,3-diferrocenylcyclopropenone with methyllithium and phenyllithium afford products of the nucleophilic opening of the three-membered ring, viz., α,β-unsaturated ketones (cis-3,4-diferrocenylbut-3-en-2-one and cis-2,3-diferrocenyl-1-phenylprop-2-enone) and allylic alcohols (cis-3,4-diferrocenyl-2-methylbut-3-en-2-ol and cis-1,1-diphenyl-2,3-diferrocenylprop-2-en-1-ol). The insertion product of a methyl(diferrocenyl)vinylcarbenoid into a σ-bond of the starting compound, viz., 2,3,4-triferrocenyl-4-(1-ferrocenyl-2-oxopropyl)cyclobutenone, along with intramolecular ortho-alkylation products, viz., 2,3-diferrocenylindanone and 2,3-diferrocenyl-2-hydroxyindanone, were also isolated. X-ray diffraction data for triferrocenylcyclobutenone and 2,3-diferrocenyl-2-hydroxyindanone are presented.     

A practical synthesis of 3-indolyl α,β-unsaturated carbonyl compounds

An acid-catalyzed practical synthesis of 3-indolyl α,β-unsaturated carbonyl compounds using methyl 3-methoxyacrylate, methyl 3,3-dimethoxypropionate, or 1,1-dimethoxy-3-butanone is reported. 35% HCl aqueous solution catalyzes this reaction efficiently in acetic acid. One of the most favorable substrates is 3-(4-fluorophenyl)-1-isopropyl-1H-indole, which reacts nearly quantitatively to give the corresponding α,β-unsaturated ester, and the scope of the reaction can be extended to some electron-rich benzene derivatives.     

Synthesis and mesomorphic properties of new liquid crystalline compounds with ß-hydroxy-, ß-chloroketone and a,ß-unsaturated ketone moieties in the terminal chains

The syntheses of new liquid crystalline compounds containing β-hydroxy-, β-chloroketone and α,β-unsaturated ketone moieties are described. The key intermediate 1-(4-hydroxyphenyl)-3-hydroxyoctan-1-one was obtained by the hydrogenolysis of the heterocycle in 3-(4-hydroxyphenyl)-5-pentyl-2-isoxazoline. Dehydratation of the intermediate β-hydroxyketone led to 1-(4-hydroxyphenyl)-oct-2-en-1-one. Reaction of 1-(4-hydroxyphenyl)-3-hydroxyoctan-1-one with hydrochloric acid yielded 1-(4-hydroxyphenyl)-3-chlorooctan-1-one. The target liquid crystalline compounds were synthesized by the esterification of these phenols with corresponding acids. The relationships between the moiety type in the terminal chain and the liquid crystalline properties are discussed.     

First synthesis of 1-aryl-4,4-dichlorobut-3-en-1-ones. The electrochemical reduction of 1-aryl-4,4,4-trichlorobut-2-en-1-ones as a key step

The first method for the synthesis of 1-aryl-4,4-dichlorobut-3-en-1-ones is reported. Treatment of acetophenones with anhydrous chloral leads to 1-aryl-4,4,4-trichloro-3-hydroxybutan-1-ones in near quantitative yields. These compounds were efficiently dehydrated with either sulfuric or p-toluenesulfonic acid to give 1-aryl-4,4,4-trichlorobut-2-en-1-ones, which were selectively converted to the title compounds in fair to quantitative yields by electrochemical reduction. The X-ray crystallographic structure of 4,4-dichloro-1-(4-methoxyphenyl)but-3-en-1-one has been determined. The preferential formation of β,γ-unsaturated ketones with total exclusion of the corresponding α,β-unsaturated isomers has been discussed with the aid of HF and B3LYP density functional theory methods.     

Synthesis and desilylation of some bis(trimethylsilyl)alkenes and polymers bearing bis(silyl)alkenyl groups

The synthesis of various vinylbis(silanes) from some aryl and heteroaryl aldehydes and (Me₃Si)₃CLi in Et₂O is described. Friedel-Crafts reaction of 1,1-bis(trimethylsilyl)-2-(2-naphthyl)ethene with various acyl chlorides (RCOCl, R = Me, Et, i-Pr, i-Bu, n-pent) gave the corresponding α-silyl-α,β-unsaturated enones with high E steroselectivity. Moreover, poly(styrene)-co-[2,2-bis(trimethylsilyl)ethenyl(styrene)] obtained via the reaction of polymers bearing pendant enone functions and (Me₃Si)₃CLi, reacts with the same acyl chlorides in the presence of catalytic amount of AlCl₃ to give the new macromolecules bearing α-silyl-α,β-unsaturated enones and α,β-unsaturated enones.     

Photocycloadditions of tetrachloro-1,4-benzoquinone (chloranil) onto cyclobutene and cyclopropene. Expected and unexpected products

Solutions of chloranil (CA) in chlorobenzene were irradiated in the presence of cyclobutene and cyclopropene. Cyclobutene gave rise to two conventional 1 : 2 cycloadducts onto the dichloroethene subunits of CA and an α,β-unsaturated α,γ-dichloro-γ-lactone. Heating of the crude product in methanol converted the lactone into an α,β-unsaturated methyl γ-oxocarboxylate (25% yield) and a large amount of the major 1 : 2 cycloadduct, which contains chlorocyclobutane entities, into a cyclopropylcarbinyl chloride derivative (24% yield). An entirely new product type was the result in the case of cyclopropene. After treatment of the crude product with methanol a tetracyclic acetal containing a cyclopentanone and a dihydropyran subunit was isolated in 36% yield. Apparently, CA had taken up two molecules of cyclopropene. One of the resulting cyclopropane entities must have undergone a rearrangement en route to the final product.     

Synthesis of trifluoromethyl-substituted salicylates by cyclocondensation of 1,3-bis(silyloxy)-1,3-butadienes with 4,4-dimethylthio-1,1,1-trifluorobut-3-en-2-one

A formal [3+3] cyclocondensation of 1,3-bis(silyl enol ethers) with the little-known 4,4-dimethylthio-1,1,1-trifluorobut-3-en-2-one was studied. In contrast to 4,4-dimethoxy-1,1,1-trifluorobut-3-en-2-one, this α-oxoketene dithioacetal reacts with 1,3-bis(trimethylsilyloxy)-1,3-butadienes in the presence of TiCl₄ to give mainly 6-methylthio-4-(trifluoromethyl)salicylates via 1,2-addition. The scope and limitations of the reaction are discussed.     

Constituents of the Heartwood of Diospyros Eriantha

The isolation and identification of fifteen compounds from the heartwood of Diospyros eriantha are described. Their structures were determined on the basis of spectral evidence and/or comparison with authentic samples. These compounds include three steroids (stigmast-4-en-3-one, stigmast-4-ene-3,6-dione, and 3β-hydroxystigmast-5-en-7-one), seven triterpenoids (friedelin, lupeol, betulinaldehyde, 3β-acetoxyurs-11-en-13,28-olide, 3β-acetoxyoleanolic acid, betulin, and betulinic acid), three quinones (2-ethoxy-7-methyljuglone, 3-ethoxy-7-methyljuglone, and 2,6-dimethoxy-1,4-benzoquinone), and two phenols (3,4,5-trimethoxyphenol, and syringic acid).     

Swallowtail bacteriochlorins. Lipophilic absorbers for the near-infrared

Bacteriochlorins absorb strongly in the near-infrared spectral region and hence are ideally suited for diverse photomedical applications, yet naturally occurring bacteriochlorins have limited stability and synthetic malleability. A de novo route has been exploited to prepare synthetic bacteriochlorins that bear a geminal dimethyl group in each pyrroline ring for stability and a symmetrically branched 1,5-dimethoxypentyl group attached to each pyrrole ring for solubility in lipophilic media.     

A novel and efficient procedure for the preparation of allylic alcohols from α,β-unsaturated carboxylic esters using LiAlH4/BnCl

A new and efficient method for the reduction of α,β-unsaturated carboxylic esters to allylic alcohols utilizing LiAlH₄/BnCl is described. Various α,β-unsaturated esters, including the coumarins bearing α,β-unsaturated lactone skeleton, can be converted smoothly into their corresponding allylic alcohols in high yields under mild conditions with short reaction times.     

Differential-pulse polarography of trichothecene mycotoxins : Determination of Deoxynivalenol,Nivalenol and Fusarenone-X in Maize

The polarographic behaviour of representative trichothecenes is described. Compounds characterized by an α,β-unsaturated carbonyl group or by a macrocyclic lactonic ring were found to be electroactive in a methanolic Britton—Robinson buffer. Differential pulse polarography provides detection limits of the order of 40 nmol l^?1 with linear ranges extending up to 9 μmol l^?1. The application of differential pulse polarography is described for the determination of nivalenol (3α, 4β, 7α, 15-tetrahydroxy-12,13-epoxytrichotec-9-en-8-one), deoxynivalenol (3α, 7α, 15-trihydroxy-12,13-epoxytrichothec-9-en-8-one) and fusarenone-X (3α, 7α, 15-trihydroxy-4 β-acetoxy-12,13-epoxytrichothec-9-en-8-one) in infected maize. A suitable liquid/liquid extraction and chromatographic cleanup procedure is reported. Detection limits for the overall procedure and for a sample size of 50 g are of the order of 50 ng g^?1 while average recoveries range from 20 to 70% at the 1 μg g^?1 level. Polarographic results are compared with those obtained by a gas-chromatographic method.     

Asymmetric transfer hydrogenation of α,β-unsaturated, α-tosyloxy and α-substituted ketones

Asymmetric transfer hydrogenation of cyclic and acyclic α,β-unsaturated ketones catalysed by η⁶-p-cymene/ruthenium(II) and η⁵-pentamethylcyclopentadienyl/rhodium(III) complexes have been investigated. Cyclic α,β-unsaturated ketones appeared to be more suitable substrates for the synthesis of enantiomerically pure allylic alcohols than do acyclic α,β-unsaturated ketones. A proposed mechanism for the formation of 4-phenyl-[1,3]-dioxolan-2-one from α-tosyloxy- and halo-substituted acetophenones is discussed. The results of further investigations into the reduction of a range of α-tosyloxyacetophenones and the dynamic kinetic resolution of α-substituted ketones is presented.     

First direct evidence of radical intermediates in samarium diiodide induced cyclization by ESR spectra

The mechanism of samarium diiodide (SmI(2))-induced cyclization of α,β-unsaturated esters and ketones to bicyclic compounds was examined using ESR spectroscopy. This is the first report of direct evidence of the radical intermediates in the SmI(2) reaction. The preferential reduction of the α,β-unsaturated carbonyl part in some substrates should be recognized as a main route.     

Synthesis of 3-isothiocyanatopropion-and-butyraldehyde diethyl acetals and their reactions with n-nucleophiles

A one-pot procedure was developed for the synthesis of 3-isothiocyanatopropionaldehyde and 3-isothiocyanatobutyraldehyde diethyl acetals from the corresponding α,β-unsaturated aldehydes. Reactions of 1,1-diethoxy-3-isothiocyanatobutane with aliphatic amines and hydrazines gave, respectively, substituted thioureas and thiosemicarbazides which underwent acid-catalyzed cyclization to form 6-ethoxytetrahydropyrimidine-2(1H)-thiones, 9,10-dimethoxy-2-methyl-1,2,3,6,7,11b-hexahydro-4H-pyrimido[6,1-a]isoquinoline-4-thiones, and 2-methyl-2,3,6,7,12,12b-hexahydropyrimido[1′,6′:1,2]pyrido[3,4-b]indole-4(1H)-thione.     

β,β-二氯丁烯酮甲基上的反应

通过4,4-二氯-3-丁烯-2-酮的氯甲基化,Mannich反应和醇醛缩合制备了1,1,5-三氯-p-戊烯-3-酮(2),1,1-二氯-9-二乙胺基-1-戊烯-3-酮盐酸盐(3)和1,1-二氯-1,4-己二烯-3-酮(4).氯甲基化产品(2)与三乙胺在醚反应生成1,1-二氯-1,4-戊二烯-3-酮(6),在醇中生成1,1-二氯-5-乙氧基-1-戊烯-3-酮(6).与容易在室温中聚合.(2)和氨在醇中反应可得到环化产品N-(4-酮基-5H,6H-2-吡啶基)-3H,4H,5H-吡啶-2,4-二酮.     

A novel hydrazide type organocatalyst for enantioselective Diels-Alder reactions

The development of a new class of hydrazide type organocatalyst, (4R,5R)-1,3-bis(isopropylamino)-4,5-dihenylimidazolidin-2-one 2a, for enantioselective Diels-Alder reactions between cyclopentadiene and α,β-unsaturated aldehydes are presented. The new organocatalyst 2a promoted the reaction, affording Diels-Alder adducts in good yields with good levels of enantioselectivity.     

Synthesis of Diastereomeric 8-Fluoro-ABC-Steroid Building Blocks

An eight-step linear sequence for the preparation of two diastereomers of an 8-fluoro-ABC-steroid building block was developed. Key step was an intramolecular Diels–Alder reaction of an intermediate o-quinodimethane formed from a benzocyclobutene substituted with a 5-fluorohex-5-en-4-one chain. This side chain was prepared from 6-chlorohex-1-ene by bromofluorination, elimination of HBr, Finkelstein reaction and alkylation of a literature-known benzocyclobutene derivative with the thus-formed 6-iodo-2-fluorohex-1-ene. Allylic oxidation of side chain's fluorovinyl moiety to an α-fluoro-α,β-unsaturated ketone completed the preparation of the precursor for the [4+2]-cycloaddition.     

4-(t-butylthio)-3-buten-2-one. Synthon for α,β- and α,β,γ,δ-unsaturated aldehyde synthesis

A convenient synthesis of α,β- and α,β,γ,δ-unsaturated aldehydes using readily accessible 4-(t-butylthio)-3-buten-2-one as synthon was described.     

Synthesis of alicyclic esters via an intramolecular conjugate addition reaction. New method for generating (Z)-vinylcopper species from 1,1-dibromoalkenes

A novel cyclization reaction of a 1,1-dibromoalkene derivative having an α,β-unsaturated ester moiety was developed. Under the influence of Me₂CuLi, the 1,1-dibromoalkene was converted into a (Z)-vinylcopper species which in turn underwent an intramolecular conjugate addition reaction with the α,β-unsaturated ester moiety. Five-, six-, and seven-membered carbocycles were constructed by the present method. The substrate having an epoxide moiety also afforded a five-membered product via a 5-exo type intramolecular cyclization reaction.     

An efficient conjugate hydrocyanation of chalcones and related enones with TMSCN under solvent- and additive-free microwave conditions

A first example of solvent- and additive-free 1,4-addition reaction of α,β-unsaturated ketones such as chalcones, 3-nonen-2-one and benzalacetone with trimethylsilyl cyanide (TMSCN) is described. The addition of TMSCN to chalcones, 3-nonen-2-one, and benzalacetone under microwave irradiation in the absence of Lewis or Brønsted acids and solvents, yielded the corresponding β-cyanoketones in good to moderate yields, as quite rapidly as in 5 min. No systematic substituent effect of chalcones on the yields was observed. No reaction of α,β-unsaturated esters such as methyl cinnamate with TMSCN took place under the same conditions.