Raman-spectrum investigation of 2-butyne-1,4-diol 2-butyne-1,4-diol diacetate,and 1,4-dichloro-2-butyne

Summary 2-Butyne-1,4-diol, 2-butyne-1,4-diol diacetate, and 1,4-dichloro-2-butyne exist in cisoid and transoid forms because of the operation of factors hindering free rotation of individual groups of atoms in these molecules around the corresponding single bonds.     

一种简便合成2-丁炔-1,4-二醇衍生物的新方法

由2-丁炔-1,4-二醇可以很方便地得到2-丁炔-1,4-二氯,这一试剂在有机合成中有着广泛的应用。而在其它条件相同的情况下,制备2-丁炔-1,4-二溴并未得到相应较好的结果。我们用无水苯为反应溶剂,以温和的 (PPh3)PBr2作为卤代试剂(冰浴下液溴逐滴滴入PPh3苯溶剂中当场生成)卤化2-丁炔-1,4-二醇,选择性合成得到2-丁炔-1,4-二溴衍生物。同时也实现了2-丁炔-1,4-二醋酸酯的合成。     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Hydroboration-oxidation of ricinoleic acid derivatives

The regioselectivity in the hydroboration-oxidation of ricinoleic acid derivatives only slightly depends on the configuration of the optically active center: the fraction of the resulting 1,3-diol is larger by 6–10% than that of the 1,4-isomer. The new asymmetric center has preferentially S configuration, as follows from the formation of the corresponding stereoisomeric 1,3-dioxane from the 1,3-diol and of 2,5-dialkyltetrahydrofuran from the 1,4-diol.     

Synthesis of 2,5-diethynyl substituted oxepins from trans-1,4-diethynylcyclohexa-2,5-diene-1,4-diols

Reaction of trans-1,4-bis(trimethylsilylethynyl)cyclohexa-2,5-diene-1,4-diol with n-BuLi followed by methanesulfonyl chloride resulted in the formation of a dark red solid, which was identified as 2,5-bis(trimethylsilylethynyl)oxepin. Deprotection of the silyl groups resulted in the formation of 2,5-diethynyloxepin, a red, shock sensitive solid. Reaction of a differentially substituted cyclohexa-2,5-diene-1,4-diol gave a mixture of 2,5-diethynyl substituted oxepins.     

The acid catalysed reaction of 1,4-diketones with hydrogen sulphide : A convenient route to substituted thiophens

Various 1,4-diketones and 2-ethoxycarbonyl-1,4-diketones have been reacted with H₂S in acidic ethanol to give 2,5- or higher substituted thiophens as resulting from a spontaneous ring-closure reaction of initially formed sulphur analogues of the starting diketones. In some the corresponding 2-mercapto-2,3-dihydrothiophens and/or 2,5-dimercaptotetrahydrothiophens were formed as by-products. 1,4-Diphenyl-1,4-diketones behaved exceptionally under similar reaction conditions yielding preferentially 2,5-diphenylfurans.     

Facile Synthesis of 2-Substituted cis-2-cyclopentene-1,4-diol Derivatives

2-Substituted cis-2-cyclopentene-1,4-diol derivatives are used as starting materials for prostaglandin synthesis¹. Two papers concerning the synthesis of these compounds have been published so far ^1,2. In this paper we would like to present an alternative method for synthesis of 2-substituted cis-2-cyclopen-tene-1,4-diols from easily available cis-2-cyclopentene-1, 4-diol diacetate 1 ³.     

Selective oxidation of acetylenic 1,4-diols with dioxiranes in comparison with the methyltrioxorhenium-hydrogen peroxide oxidant

Dimethyldioxirane (1a) and its trifluoro analog (1b) were employed to achieve selectively the direct transformation of hex-3-yne-2,5-diol 3a and 1,4-diphenyl-but-2yne-1,4-diol 3b (two representative acetylenic 1,4-diols) into the corresponding carbonyls, leaving the carbon-carbon triple bond moiety untouched. The results are compared with those recorded in the analogous oxidation using the methyltrioxorhenium (MTO)/85% H₂O₂ homogeneous system. The powerful methyl(trifluoromethyl)dioxirane (1b) is the reagent of choice to achieve optimum yields of the target alkyne-1,4-diones, which are extremely versatile synthons.     

Catalytic synthesis of dihydrofurans (review)

Various methods for the preparation of 2,3-dihydrofuran, 2,5-dihydrofuran, 2-methylenetetrahydrofuran, and their alkyl and aryl derivatives are examined. The most promising method for the preparation of 2,3-dihydrofuran is the conversion of 1,4-butanediol on cobalt catalysts. 2,5-Dihydrofuran is obtained by dehydration of 2-butene-1,4-diol on Al₂O₃, cobalt-containing and other catalysts, while 2-methylenetetrahydrofuran is obtained by dehydrohalogenation of tetrahydrofurfuryl halides. The various methods for the isomerization of 2,5-dihydrofuran to 2,3-dihydrofuran are discussed. Examples of the application of dihydrofurans in organic synthesis are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1299–1311, October, 1982.     

Ein einfacher Zugang zu 4-hydroxy-2,5-dimethyl-3(2H)-furanon (furaneol), einem Aromabestandteil von Ananas und Erdbeere

Furaneol®

1 Registered trade mark of Firmenich SA.

[4-hydroxy-2,5-dimethyl-3(2H)-furanone ( 1 )], a flavour component of pineapple and strawberry, has been prepared by a two-step synthesis starting with readily available 3-hexyne-2,5-diol. By the same method 4-hydroxy-5-methyl-3(2H)-furanone ( 2 ) and 2-ethyl-4-hydroxy-5-methyl-3(2H)-furanone ( 3a ) have been prepared from 2-pentyne-1,4-diol and 3-heptyne-2,5-diol, respectively.     

Synthesis of eight-membered aminocyclitol analogues

The first syntheses of four stereoisomeric diaminocyclooctane diols, as well as a chlorocyclooctane aminodiol, are reported. In the first part, photooxygenation of cis,cis-1,3-cyclooctadiene gave a bicyclic endoperoxide, which was reduced with zinc followed by mesylation of the hydroxyl groups. Treatment with sodium azide afforded 1,4- and 1,2-cyclooctene diazides. Oxidation of the double bonds in the isomeric diazides with OsO₄, followed by hydrogenation of the azide groups, led to 3,8-diaminocyclooctane-1,2-diol and 3,4-diaminocyclooctane-1,2-diols. In the second part, cis-3,8-diazidocyclooctene was converted into the corresponding epoxide. Stereospecific hydrolysis of the epoxide ring with HCl_(g) in methanol, and hydrogenation of the azide groups gave 3,8-diamino-2-chloro-cyclooctan-1-ol. Bromination of the double bond in cyclooctene diacetate, followed by acetate deprotection, azidolysis of the bromides, and hydrogenation of the azide groups resulted in the formation of 2,3-diaminocyclooctane-1,4-diol.     

Base-catalyzed cascade 1,6-sulfur-Michael/Henry reaction of trifluoromethyl-substituted styrylisoxazoles: Diastereoselective synthesis of tetrahydrothiophenes with a trifluoromethylated quaternary center

An effective diastereoselective [3+2] annulation of 1,4-dithiane-2,5-diol to trifluoromethyl-substituted styrylisoxazoles catalyzed by DABCO is described, giving highly functionalized tetrahydrothiophenes containing trifluoromethylated quaternary center in excellent yields and diastereoselectivities.     

An alternative synthesis of benzobis(imidazolium) salts via a ‘one-pot’ cyclization/oxidation reaction sequence

Cyclization of N-aryl and N-alkyl 2,5-diamino-1,4-benzoquinonediimines using paraformaldehyde under acidic conditions followed by oxidation with catalytic amounts of Pd(OAc)₂ afforded their respective benzobis(imidazolium) salts in yields of 48-98%. A comparative solid-state study between a 2,5-diamino-1,4-benzoquinonediimine and its corresponding benzobis(imidazolium) dichloride was also performed.     

Enantioselective photocyclization of amides to beta-lactam derivatives in inclusion crystals with an optically active host

Irradiation of inclusion crystals of 2-(N-acyl-N-alkylamino)cyclohex-2-enones and N,N-dimethylphenylglyoxylamide with chiral host molecules gave the optically active N-alkyl-1-azaspiro[3.5]-nonane-2,5-diones and 3-hydroxy-1-methyl-3-phenylazetidin-2-one, respectively. The crystal structure of the 1:1 inclusion complex of N,N-dimethylphenylglyoxylamide with (-)-trans-1,4-bis[3-(o-chlorophenyl)-3-hydroxy-3-phenylprop-1-ynyl]-2,3,5,6- tetrachloro-2,5-cyclohexadiene-1,4-diol was analyzed by X-ray diffraction.     

A facile and efficient approach for the synthesis of 3-arylthiazol-2(3H)-one

A facile and efficient method for synthesis of 3-arylthiazol-2(3H)-one through the reaction of acyl azide and 1,4-dithiane-2,5-diol was reported. This reaction proceeded at 80?°C at first and then in acidic condition at room temperature, to afford products in good yields for a wide range of substrates and a possible mechanism has also been proposed.     

Domino reactions in water for the stereoselective synthesis of novel spiro dihydro-2′H-[indene-2,3′-thiophen]-1(3H)-ones with three contiguous stereocenters

The domino reactions of (E)-2-(aryl)-2,3-dihydro-1H-inden-1-ones and 1,4-dithiane-2,5-diol in the presence of triethylamine in water stereoselectively afforded a library of 2′-(aryl)-4′-hydroxy-4′,5′-dihydro-2′H-spiro[indene-2,3′-thiophen]-1(3H)-ones. This transformation presumably proceeds via the generation of 2-mercaptoacetaldehyde from 1,4-dithiane-2,5-diol followed by Michael addition–intramolecular aldol sequence with C–C and C–S bond formations and creation of three contiguous stereocenters in a one-pot operation.     

Access to thiomorpholin-3-one derivatives: [3 + 3]-cycloadditions of α-chlorohydroxamates and 1,4-dithiane-2,5-diol

A protocol of [3 + 3]-cycloaddition was proposed for the synthesis of 2H-1,4-thiazin-3(4H)-ones and thiomorpholine-3,5-diones from α-chlorohydroxamates and 1,4-dithiane-2,5-diol. This direct and practical method provides a novel and rapid approach for the synthesis of thiomorpholin-3-one derivatives under mild condition with moderate to good yield and wide functional group tolerance.     

The preparation of (1alpha,3beta)-3-hydroxycholestane-4,6-diene- 1,25-diol diacetate from a 5,7-diene precursor: a new method for the synthesis of heteroannular dienes

Starting from the 7alpha-bromide 5a, a regioselective synthesis of (1alpha,3beta)-3-hydroxycholestane-4,6-diene-1,25-diol diacetate (2) is described. The preparative removal of contaminating 5,7-diene 9 was accomplished by the formation of the corresponding Diels-Alder adduct 11. Acetylation of the diacetate 2 followed by acid-catalyzed elimination and rearrangement yielded styrene 13.     

Nickel-catalyzed indium(I)-mediated double addition of aldehydes to 1,3-dienes

In the presence of InI, Ni(acac)2 and PPh3, several 1,3-dienes were reacted with two molecules of aldehyde to give the corresponding 1,4- and 1,6-diols. The regioselectivity of the 1,4-/1,6-diol was efficiently regulated by the addition of water; the 1,6-diol was obtained selectively in dry THF, whereas the 1,4-diol was obtained predominantly in DMI containing a small amount of water.     

Determination of organic substances by standard chromous chloride solution

The reducibility of a number of organic compounds by a standard chromous chloride solution, prepared determinately from potassium dichromate, has been studied. Orange II, tartrazine, and azoxybenzene (after rearrangement in sulfuric acid medium to the corresponding azo compound) were quantitatively cleaved to the corresponding amines, while azobenzene was reduced only to hydrazobenzene (extent of reduction uncertain). Also quantitatively reduced were: propiolic acid to propenoic acid, diacetyl to acetoin, and benzil to benzoin. Hydrazobenzene, diphenylacetylene, 2-methyl-3-butyn-2-ol, 1-ethynyl-cyclohexanol-1, 2,5-dimethyl-3-hexyne-2,5-diol, 2,5-diphenyl-3-hexyne-2,5-diol, and acetylacetone were not reduced even at elevated temperatures.