Synthesis of (Z)- and (E)-3,4-Dimethyl-hex-3-ene-1,6-diols

(Z)- and (E)-3,4-dimethyl-hex-3-ene-1,6-diols (1 and 2) have been synthesized in 23% and 68% yields by a three step sequence requiring only one purification at the end. The steps are a) coupling of 2-lithio-1,3-dithiane with (Z)- or (E)-1,4-dibromo-2,3-dimethyl-but-2-ene (3 or 4), b) hydrolysis of the thioketals (8 and 9) with methyl iodide in a mixture of acetonitrile, acetone and water to give the 3,4-dimethyl-hex-3-ene-1,6-diols (10 and 11) and c) reduction with diisobutylaluminum hydride to provide the (Z)- and (E)-diols.     

Studies on the Wittig Reaction (IV) A Stereoselective Synthesis of the Insect Sex Pheromone of Laspeyresia pomonella,E,E,-8,10-Dodecadien-1-ol

Abstract

The Wittig reaction was widely used in the synthesis of natural products particularly in the area of insect pheromore synthesis. But unfortunately when a moderated triphenylphosphonium ylid is used, the resultant compound is a impractical E, Z, mixture. For instance, the title compound was once synthesized by the Wittig between butenylidene triphenylphosphorane and 8-oxo-octanoate, followed by hydrolysis and reduction. The product was a mixture containing 75% 8E,10E, isomer and 25% 8Z,10E isomer. Recently we have reported that a simple change in phosphorus substituents from Ph₃P=CHR to Ph₂(RCH₂)P=CHR(R′=alkenyl or H) dramatically increases the proportion of Eolefin formed from moderated ylides(R=alkenyl) and aliphatic aldehydes. According to this fact, here we report a stereoselective synthesis of E,E,-8,10-dodecadien-1-ol from butenylidene methyl diphenylphosphorane and 8-oxo-octanoate in the absence of lithium salt(Schemel). After hydrolysis and reduction, the title compound containing 94.7% 8E, 10E isomer was obtained. This approach affords a convenient synthesis for insect pheromones bearing a E,E,conjugated diene moiety. This experimental fact once again illustrates the stereochemistry of allylic diphenylphosphonium ylid is quite different from the corresponding triphenylphosphonium one.     

N-(R-Cyclopropyl) Trifluoroacetimidoyl Phosphonates

Abstract

A convenient synthetic approach for previously unknown N-(R-cyclopropyl)trifluoroacetimidoyl phosphonates 5a,b (R?H, CF₃) was developed on the basis of the reaction of respective trifluoroacetimidoyl chlorides with triethyl phosphite. It was shown that imidoyl phosphonates 5a,b exist as equilibrium mixture of Z/E isomers (Z:E ～92:8). Activation parameters of Z–E isomerization were evaluated by ¹⁹F NMR spectroscopy. Catalytic hydrogenation of 5a,b can serve as a convenient method for the synthesis of trifluoroethylaminophosphonates with a rigid N-cyclopropyl group.     

Studies on the Wittig Reaction (V) Trans Stereoselectivity in the Reaction of Benzylidene Alkyl Diphenylphosphorane and Aldehydes

Abstract

In previous papers, we reported the E-selectivity in the Wittig reaction of phosphorus ylid of the general formula Ph₂R′CH₂P=CHR (R=alkenyl; R′=H, alkenyl) and aldehydes. This continuing research for the stereochemistry of diphenylphosphorane in the title reaction of Ph₂R′CH₂P=CHR and R″CHO, where R=Ph, R′=H,Ph and R″=Ph,p-substituted phenyl, has led to thosimilar results. However, the E-selectivity is dependent on the ylid structure, reaction condition and the nature of the substituents on the aromatic ring. Generally the effect is stronger with benzyl diphenylphosphorane(R=H), the proportion of E olefin is produced in a larger quantity in salt-free condition than in the salt-containing medium, and the aromatic aldehyde bearing an electronwithdrawing group on the ring gives a higher E/Z ratio. Moreover, we also found that the logarithms of the E/Z ratio of the substituted stilbene products are linear with the σ constant of the substituents of the aromatic aldehydes: log E/Z=aσ+ b     

Synthesis of Vinyl Sulfones from Aryl Methyl Ketones Under Sonochemical Conditions and Formation of Allyl Sulfones

An efficient synthesis of vinyl sulfones 3a-o from aryl methyl ketones 2 bearing an electron withdrawing group and the phosphonic ester 1 under sonochemical conditions is reported. These compounds are generally obtained as an E/Z mixture. Formation of the allyl sulfones 4 is also observed.     

Synthetic Applications of Stereodefined 2-Substituted 1-Silyl-1-stannylethenes: A New Synthesis of 5-Ethenyl-5′-(1-propynyl)-2,2′-bithiophene,a Naturally-Occurring Phototoxin)

(E)-2-(5-Trimenthylstannyl-2-thienyl)ethenyldimethylphenylsilane. (E)-8, which can be stereospecifically prepared from (Z)-1-dimethylphenylsilyl-2-(2-thienyl)-1-trimethylstannyl-ethene, (Z)-6, or from (E)-2-(2-thienyl)ethenyldimethylphenylsilane, (E)-9, serves as an equivalent to the 2-ethenylthiophene d ¹', d ⁵-synthon, 20, in an efficient two-step synthesis of 5-ethenyl-5′-(1-propynyl)-2,2′-bithiophene, 10, a naturally-occurring phototoxin. In the first step of this synthesis compound (E)-8 undergoes a palladium-catalyzed cross-coupling reaction with 2-iodo-5-(1-propynyl)thiophene, 16, and in th second step the so obtained cross-coupling product, (E)-17, undergoes a protodesilylation reaction.     

Investigation on the Ring-Opening Reactions of 3-(1H-1,2,4-Triazol-1-yl)1,5-benzothiazepines with Arylonitrile Oxides

Abstract

Novel ring opening compounds, (Z)-2-((Z)-((E)-1,3-diaryl-2-(1H-1,2,4-triazol-1-yl)allylidene)amino)aryl N-hydroxybenzimidothioates 4a–r, were obtained from the reaction of 2,4-diaryl-3-(1H-1,2,4-triazol-1-yl)-2,5-dihydro-1,5-benzothiazepines 3a–f and arylonitrile oxides. The structure of these products has been elucidated by spectroscopic analysis and, in one case, X-ray crystallographic analysis. According to the result, it was presumed that this reaction did not proceeded through 1,3-dipolar cycloaddition reaction.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

GRAPHICAL ABSTRACT      

A New Facile One-Pot Synthesis of Cyclopropyl Vinyl Sulfides

Abstract

The (Z) and (E) diastereoisomers of cyclopropylvinyl sulfides are efficiently prepared by treatment of (phenylthiomethyl)trimethylsilane with γ-chlorobutyrophenones in the presence of LDA at ?78°C. C3 ring closure and olefination by Peterson reaction occur in the same step.     

Preparation of gamma-siloxyallyltributylstannanes and their use in the synthesis of (+/-)-1-deoxy-6,8a-di-epi-castanospermine

gamma-siloxyallyltributylstannanes were selectively obtained as E or Z isomers from beta-tributylstannylacrolein upon reaction with lithium or magnesium alkylcyanocuprates. The ability of the reagents to give a high syn selectivity when added to iminium salts has been used for the efficient synthesis of (+/-)-1-deoxy-6,8a-di-epi-castanospermine from succinimide. The key step of the synthesis was the allylstannation of the N-allyliminium intermediate followed by ring closing metathesis.     

SYNTHESES AND MASS SPECTRAL REARRANGEMENTS OF UNSATURATED BIS-SULPHIDES AND BIS-SULPHONES

Abstract

The synthesis of (E)- and (Z)-1.2-bis(p-fluorophenylsulphenyl)stilbenes (2a and 2b) and 1,2-bis(p-fluorophenylsulphonyl)stilbenes (3a and 3b) was carried out and their configurations were consistent with their stereospecific synthesis. The isomeric 1,1-bis(p-fluorophenylsulphenyl)- and 1,1-bis(p-fluorophenylsulphonyl)-2,2-bis(phenyl)ethylenes (8 and 9) were also synthesised and configurations were established by degradative oxidation. Mass spectral rearrangements of all these compounds were examined. Mass spectra of 1,1-bis-sulphide and 1,1-bis-sulphone bears close relationship with those of (E)- and (Z)-isomeric counterparts. Smiles-type rearrangement observed in 1,2-bis-sulphides was absent in 1,2-bis-sulphones. McLafferty-type rearrangement involving hydrogen migration, from aryl group was noticed in both bis-sulphides and bis-sulphones. Vinyl migration to the sulphone oxygen predominates over aryl migration in three isomeric bis-sulphones.     

Synthesis of the Aliphatic Subunit of the Macrolide LL‐Z 1640‐2 via Vasella Ring Opening of a 6‐Iodo‐4‐deoxy‐D‐mannose

The synthesis of the aliphatic subunit 9 of the macrolide LL‐Z1640‐2 (I), starting from a 4‐deoxy‐D‐mannose derivative 2a, is described. The procedure includes the first successful application of a Vasella ring opening reaction for a 4‐deoxypyranoside. Nucleophilic addition of an alkynyllithium reagent to the aldehyde 4 led to the propargylic alcohol 7, which was converted to the advanced building block 9 in two further steps.     

Stereocontrolled Conversion of 3,5-Dioxopyrrolizidine Into (Z)- and (E)- 5-Acetonylpyrrolizidin-3-ones

Stereocontrolled synthesis of (Z)-5-acetonyl-pyrrolizidin-3-one (4) and (E)-isomer 5 from 3,5-dioxopyrrolizidine 1 is described.     

Total synthesis of (-)-salicylihalamide A

[see structure]. A 16-step synthesis of the novel cytotoxin salicylihalamide A (1E) has been achieved in 3.3% overall yield using ring closing metathesis to generate the macrolide and addition of (1Z,3Z)-hexadienylcuprate (2), which was generated in situ from ethylcuprate and acetylene, to alkenyl isocyanate 3 to form the side chain.     

Construction of eight-membered ether rings by olefin geometry-dependent internal alkylation: first asymmetric total syntheses of (+)-3-(E)- and (+)-3-(Z)-pinnatifidenyne

The first and highly stereoselective asymmetric total syntheses of eight-membered ring ether marine natural products (+)-3-(E)-pinnatifidenyne and (+)-3-(Z)-pinnatifidenyne have been accomplished. Notable features of our syntheses include a novel and efficient construction of oxocene 5 by a highly stereo- and regioselective internal alkylation and direct ketone synthesis of ketone 16 from the alpha-alkyloxy amide moiety in oxocene 5.     

Synthesis and reactivity of E,Z butadiene-iron tricarbonyl complexes.

The synthesis, structure and thermal stability of the E,Z butadiene-iron tricarbonyl complex 1 is reported. This complex reacts with organometallic nucleophiles in a stereoselective synthesis of functionalized E,Z dienes.     

Sex Pheromone of Chilo Suppressalis: Efficient Syntheses of (Z)-11-Hexadecenal, (Z)-13-Octadecenal And (Z)-9-Hexadecenal

The constituents of the sex attractant pheromone of Chilo suppressalis: (Z)-11-Hexedecenal 1, (Z)-13-octadecenenal 2 and (Z)-9-Hexadecenal 3 have been synthesized as their ethylene acetals 19, 15 and 13, in six steps from easily available compounds. The synthetic methodology can be applied to preparative scale.     

Convenient and Regiospecific Method for Synthesis of 4,5-Diaryl-1-methyl-2-(methylthio)-1H-imidazole

A convenient, high-yielding, regiospecific synthesis of 1H-imidazole-2-thiones ring has been developed. In addition, a series of 4,5-diaryl-1-methyl-2-(methylthio)-1H-imidazoles 8 were synthesized and characterized. The structure of regioisomers was confirmed through nuclear Overhauser effect spectroscopy and NMR spectroscopy.

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(E)- and (Z)-1-benzenesulfonyl-4-trimethylsilyl-2-butenes as (E)-1-(1,3-butadienyl) synthons

(E)- and (Z)-1-benzenesulfonyl-4-trimethylsilyl-2-butenes (E/Z=9), prepared from 4-trimethylsilyl-1-buten-3-ol, $\text{n}$-butyllithium and benzenesulfenyl chloride and oxidation of the intermediate (E)- and (Z)-1-benzenesulfinyl-4-trimethylsilyl-2-butenes with hydrogen peroxide, react with $\text{n}$-butyllithium and then primary halides to give 4-benzenesulfonyl-1-trimethylsilyl-2-alkenes which are rapidly 1,4-debenzenesulfonyltrimethylsilated to (E)-1,3-alkadienes by tetra-$\text{n}$-butylammonium fluoride at O°C.     

Synthesis of α-Alkylidene-β-Ethoxycarbonyl Cyclopentanones and -γ-Butyrolactones

Synthesis of (E,Z)-α-Alkylidene-β-ethoxycarbonyl cyclopentanones 5 and (E,Z)-α-alkylidene-γ-butyrolactones 7 by condensing phosphonates 3 or 6 with a variety of aldehydes in the presence of aqueous potassium carbonate (6-10M) as base is reported.