Efficient synthesis of alkyl (Z)-2-bromo-2-phenylvinyl tellurides from tellurium tetrabromide and phenylacetylene

Russian Journal of Organic Chemistry -     

Stereoselective synthesis of (Z)-alkene-containing proline dipeptide mimetics

In peptides and proteins, the peptide bond between an amino acid and proline exists as an equilibrium mixture of the cis-imide and trans-imide due to the low energy barrier in their interconversion. This feature greatly influences the structure and function of the proline-containing peptides and proteins. Therefore, restricting the amide bond with an (E)- or (Z)-alkene should provide a promising method for elucidating the structure-activity relationships of the peptide and the proteins. In this report, the regio- and stereoselective synthesis of cis-alanylproline (Ala-Pro) type (Z)-alkene dipeptide mimetic is described. The key steps of this synthesis are to introduce a C3 unit onto a gamma-phosphoryloxy-alpha,beta-unsaturated-delta-lactam with an organocopper-mediated anti-S(N)2' reaction and subsequently construct a five-membered proline-like cyclic structure with an intramolecular Suzuki coupling reaction. Hydrolysis of the amide bond in the resulting bicyclic lactam yields the desired cis-Ala-Pro type (Z)-alkene dipeptide isostere. The presented synthetic methodology should be applicable to the general syntheses of other cis-aminoacylproline type (Z)-alkene dipeptide mimetics.     

Stereoselective synthesis of (Z)-2-fluoro-1-alkenyl(phenyl)iodonium tetrafluoroborates

[reaction: see text] (Z)-2-Fluoro-1-alkenyl(phenyl)iodonium salts were stereoselectively prepared by the reaction of alkynyl(phenyl)iodonium salts with aqueous HF in good yields. The method is applicable to the synthesis of fluoroalkenyliodonium salts having functional groups such as ketone, ester, and chloride. (Z)-2-Fluoro-1-alkene, (Z)-2-fluoro-2-alkenoate, and (Z)-beta-fluoroenyne could be stereoselectively prepared from the fluoroalkenyliodonium salt.     

Stereoselective preparation of (E)- and (Z)-alpha-fluorostilbenes via palladium-catalyzed cross-coupling reaction of high E/Z ratio and (Z)-1-bromo-1-fluoroalkenes

A highly stereoselective method to prepare both (E)- and (Z)-alpha-fluorostilbenes is described. 1-Bromo-1-fluoroalkenes (E/Z approximately 1:1), a readily available starting material, isomerizes to high E/Z ratios by storage at -20 degrees C or by photolysis at 254 nm. Stille coupling between these high E/Z 1-bromo-1-fluoroalkenes and aryl stannanes gave (Z)-alpha-fluorostilbenes in high stereoselectivity. (Z)-1-Bromo-1-fluoroalkenes, which were kinetically separated from 1-bromo-1-fluoroalkenes (E/Z approximately 1:1), can participate in Suzuki coupling reactions to give (E)-alpha-fluorostilbenes stereoselectively.     

New polyfluorinated organotin reagents. Stereoselective synthesis of (Z)-alpha-fluoro-beta-trifluoromethylvinylstannanes

[reaction: see text] A new methodology for the synthesis of (Z)-alpha-fluoro-beta-trifluoromethylvinylstannanes, which are useful polyfluorinated organotin reagents for the synthesis of fluorine-containing biologically active compounds, is described.     

Stereoselective synthesis of 2-deoxy-beta-galactosides via 2-deoxy-2-bromo- and 2-deoxy-2-iodo-galactopyranosyl donors

[reaction: see text] A series of 2-bromo- and 2-iodo-galactopyranosyl acetates and trichloroacetimidates were evaluated as glycosyl donors for the synthesis of 2-deoxygalactopyranosides. The best selectivity for the beta-glycosidic linkage was achieved by using 6-deoxy-3,4-carbonate-protected galactosyl donors.     

Stereoselective synthesis of decarestrictine D from a previously inaccessible (2Z,4E)-alkadienyl alcohol precursor

[reaction: see text] The core structure of decarestrictine D was constructed by stereoselective oxygenation of (2Z,4E)-alkadienyl alcohol, which could be synthesized by a nickel-catalyzed coupling reaction between the corresponding cis bromide and trans borate. Efficiency in macrocyclization of the seco acid with Yamaguchi reagent was found to be protective-group-dependent, and the best yield of 40% was obtained with the seco acid with tri-MOM protective groups.     

Stereoselective Synthesis of (Z)-2-Acylamido-4-phenylcrotonates

Stereospecificsynthesisof(Z)-a,o-dehydroaminoacidsisofgreatimportanceinthepreparationofuncommonornatUralopticallypureaminoacids,because,ingeneral,(Z)-isomersaffordmuchhigherenantioselectivitieswithfasterratesthan(E)-isomersinthecatalyticasymmetrichydrogenation'.(Z)-isomersofethyl2-acylamido-4-phenylcrotonate2areimpoFtantprecursorsinthecourseofoursynthesisofL-homopheny1alaninel,akeysynthonformostcommerciallyimportantantihypertensiveACEinhibitorssuchasEnalapril,Benazepril,Lisinopril.Hereinwe…     

Stereoselective synthesis of (E)- and (Z)-beta-bromostyrene containing trifluoromethyldiazirine for photoaffinity labeling

Summary A convenient procedure for the synthesis of (E)- and (Z)-beta-bromostyrene containing trifluoromethyldiazirine is described, which involves the stereoselective reduction of the corresponding trifluoromethyldiazirinyl beta,beta-dibromostyrene without damaging the photophor. The synthetic route easily introduced deuterium, which can be utilized for the detection of a photolabeled component by MS spectrometry, after construction of a trifluoromethyldiazirinyl skeleton.     

Stereoselective synthesis of (E)- and (Z)-Fluoroalkenylboronates using 2-fluoroalkylideneiodonium ylides generated from (2-fluoro-1-alkenyl)iodonium salts

(E)- and (Z)-(fluoroalkenyl)boronates were prepared stereospecifically by the reaction of 2-fluoroalkylideneiodonium ylide generated from (E)- or (Z)-(2-fluoroalkenyl)iodonium salts with di(p-fluorophenoxy)alkylboranes, followed by transesterification to pinacol esters. The resulting pinacol esters of (fluoroalkenyl)boranes were used for the stereoselective synthesis of trisubstituted fluoroalkenes by cross-coupling reactions.     

Stereoselective synthesis of (Z)-alpha-haloacrylic acid derivatives, and (Z)-haloallylic alcohols from aldehydes and trihaloesters or amides promoted by Rieke manganese

A Mn*-promoted sequential process directed toward the synthesis of (Z)-alpha-halo-alpha,beta-unsaturated esters or amides is described. In both cases, the process takes place with complete Z-stereoselectivity. In addition, (Z)-alpha-chloro-alpha,beta-unsaturated ketones and carboxylic acids, and (Z)-haloallylic alcohols were readily prepared from (Z)-alpha-halo-alpha,beta-unsaturated amides derived from morpholine, or esters. A mechanism has been proposed to explain the sequential process and the stereoselectivity observed.     

Palladium(II)-catalyzed S(N)2' reactions of alpha-allenic acetates. Stereoconvergent synthesis of (Z,E)-2-bromo-1,3-dienes.

The reaction of acetylated alpha-allenic alcohols with LiBr in the presence of 1.5 mol % of Pd(OAc)(2) provides easy access to substituted (Z,E)-2-bromo-1,3-dienes in good yields with excellent diastereoselectivity. Both secondary and tertiary acetates as well as terminal and nonterminal allenes were studied to investigate the scope and the limitations of the reaction. A mechanism is proposed to clarify how a diastereomeric mixture of the starting compound is transformed into a single diastereomer of the product.     

Reaction of 1-bromovinyl and 1-bromo-2-phenylvinyl sulfones with some CH acids

Benzyl, methyl, and phenyl α-bromovinyl sulfones reacted with malononitrile and dimethyl malonate sodium enolates in THF to give sulfonyl-substituted cyclopropanes. Reactions of the same sulfones with methyl acetoacetate sodium enolate afforded the corresponding sulfonyl-substituted cyclopropanes as mixtures of cis and trans isomers with a small impurity of 5-sulfonyl-4,5-dihydrofuran derivative. Phenyl and p-tolyl 1-bromo-2-phenylvinyl sulfones reacted with methyl acetoacetate sodium salt to produce a mixture of trans-isomeric 5-sulfonyl-4,5-dihydrofuran and Michael adduct of the CH acid with activated acetylene generated by concurrent 1,2-dehydrobromination of the initial α-bromovinyl sulfone.     

Stereoselective one-pot synthesis of substituted (4Z)-2-alkyl-4-benzylidene- 4H-1,3-benzothiazines

Substituted (4Z)-4-benzylidene-2-methyl-4H-1,3-benzothiazines (1). and (4Z)-2-ethyl-4-benzylidene-4H-1,3-benzothiazines (2). were synthesized by direct stereoselective reactions of S-phenyl ethanethioate or S-phenyl propanethioate with substituted benzyl nitriles in the presence of triflic anhydride.     

立体专一性地合成Z-式2-烷氧羰基氨基-4-苯基-2-丁烯酸及酯

通过酸、碱催化异构化不稳定的Ｅ－异构体，从β－苯乙醇出发，经４步反应高度立体选择性地合成了Ｚ－脱氢氨基酸衍生物，Ｚ－式含量可达高达９９％以上。     

Regio- and Stereoselective Synthesis of (Z)-2-Chloro-2-phenyl-1-propylethenyltellanes

Russian Journal of Organic Chemistry - The regio- and stereoselective reaction of tellurium tetrachloride with 1-phenylpent-1-yne was used to develop efficient methods of synthesis of...