Stereospecific synthesis of divinyl selenides nucleophilic substitutions of unactivated vinyl halides by vinyl selenide anions

Vinyl alkyl selenides can be dealkylated by nucleophilic substitution or by electron transfer to give vinyl selenide anions which retain the configuration of the starting products. The same anions are also produced by electron transfer from vinyl acetyl selenides. The vinyl selenide anions react with vinyl halides, in DMF or DMA, to give divinyl selenides. These reactions occur with retention of configuration and represent a new example of nucleophilic substitutions of unactivated vinyl halides.     

Stereospecific synthesis of divinyl diselenides from vinyl acetyl selenides

Vinyl halides react with MeSeLi in DMF to afford vinyl methyl selenides which are demethylated by the excess of the MeSeLi; the vinyl selenide anions thus obtained react with acetyl chloride to give vinyl acetyl selenides. This three steps one pot synthesis occurs with complete retention of configuration. The vinyl acetyl selenides are cleanly fragmented by electron transfer to the vinyl selenide anions; addition of iodine to the resulting solutions produced the divinyl diselenides with retention of configuration. The transformation of vinyl acetyl selenides into divinyl diselenides can also be induced by catalytic amounts of a solution of sodium in HMPA or of sodium methanethiolate.     

Free radical telluroacylative addition of telluroesters to terminal alkynes

Vinyl selenides and tellurides are important precursors of many kinds of organic compounds, particular the substituted alkenes that occurred in many biologically active compounds as skeleton structures. Thus the study of vinyl selenides and tellurides has attracted considerable attention in recent years. The bifunctional addition reactions involving selenium and tellurium moieties are the latest methods for preparation of vinyl selenides with various functional groups. Recently we have reported the selenocarbonylation of alkynes with selenoesters catalyzed by cuprous halides. Nevertheless the similar bifunctional addition involving tellurium atoms has not been reported. Considering the C-Te bonds are easier to be broken than corresponding C-Se bonds, the vinyl tellurides containing electron-withdrawing groups may have particular reactivity and application in the preparation of substituted alkenes. Herein we describe the synthesis of β-aryltelluro-α,β-unsaturated ketones via bifunctional addition.     

A Facile One-pot Method for the Synthesis of Vinyl Ethers from 2-Hydroxyalkyl Phenyl Selenides

chloride instead of primary or secondary organic halide, only 21% isolated yield of 1-tert-butoxy-1-phenylethene was obtained. Obviously, t-butyl chloride would tend to mainly take place the elimination reaction rather than the substitution reaction under sodium alkylate. Scheme 1 R1OHPhSe R2R3CHX 2NaH/THFR1OPhSeCHR2R3R1 OCHR2R3H2O21 3 4 Table 1 Preparation of vinyl ethers from 2-hydroxyalkyl phenyl selenides Entry R1 R2R3X Product a Yield (%) b 1 C6H5 CH2=CHCH2Br 4a 83 …     

New synthesis of vinyl selenides nucleophilic substitutions of unactivated vinyl halides by selenide anions

Alkyl and aryl selenide anions react with unactivated vinyl halides, in dipolar aprotic solvents, to give alkyl or aryl vinyl selenides in good yields. These reactions are stereospecific and occur with retention of configuration.     

Lipase-catalyzed resolution of β-hydroxy selenides

Eleven β-hydroxy selenides were kinetically resolved using an immobilized lipase (Amano PS-C II) in toluene in the presence of vinyl acetate at 30 °C. This approach provided, in several cases, both enantiomers in high enantiomeric excess. The role of the size of substituents and the behaviour of cyclic β-hydroxy selenides is also discussed. Enantiopure β-hydroxy selenides are useful building blocks. As an application of this chemistry, enantiopure (1S,2R)-indene oxide was obtained in one step from the proper enantiopure β-hydroxy selenide.     

Lanthanum-catalyzed stereoselective synthesis of vinyl sulfides and selenides

Lanthanum oxide/TMEDA-catalyzed cross-coupling of vinyl halides with thiols/diphenyl diselenide in anhydrous DMSO and KOH is reported. Utilizing this protocol various vinyl sulfides and selenides were synthesized in excellent yields with retention of the stereochemistry. The catalyst was recyclable.     

Hypervalent Iodine in Synthesis 44: Stereoselective Synthesis of Vinylic Selenides by the Reaction of Sodium Selenolates with Vinyl (Phenyl) Iodonium Salts

Vinylic selenides have been prepared stereoselectively by the reaction of sodium selenolates with vinyl(phenyl)iodonium salts with retention or inversion of the configurations.     

Synthesis of α-Seleno Substituted Semistabilized Arsonium Ylide and Its Wittig Reaction

-SeIen0substitutedphosphoniumylidesaredifficuItt0undergoWittigreaction.1'2Wefirstlysynthesizeda-selen0substitutedstabilizedars0niumylidesandfoundthattheycouldunderg0Wittigreacti0nssm00thly."'Asthec0ntinuati0n0f0urresearch,weat-temptedtosynthesizeQ-selenosubstitutedsemistabilizedarsorniumylideandexploreditsWittigreaction.Addingdr0pwisephenylselanylbr0mide2t02equivalentsof4-nitrobenzylidenetriphenylars0ranelinmethanol,wefoundthatthetransylidati0nreactiont0okplacerapidly.Whenthereacti0ntempera…     

Nucleophilic vinylic substitutions on unactivated substrates. : The behaviour of styryl alkyl sulphides and selenides towards sulphur and selenium nucleophiles.

Sodium alkanethiolates or lithium methyl selenide react with styryl alkyl sulphides and selenides, in DMF at 100°C, to give the products of vinylic or aliphatic substitution. The two nucleophilic reagents are extremely selective. In the case of RSNa the attack at the vinylic carbon atom is much faster than that at the aliphatic carbon atom and the (Z)- or (E)- styryl alkyl sulphides are obtained as the result of a stereospecific vinylic substitution which occurs with retention of configuration. On the contrary, in the case of MeSeLi, under the same experimental conditions, the only reaction occurring is the aliphatic substitution which affords the vinyl thiolate anions, as an equilibrium mixture of the (E)- and (Z)- isomers, or the vinyl selenide anions which retain the configuration of the starting styryl alkyl selenides.     

Studies on the oxidation of hydrazones with iodine and with phenylselenenyl bromide in the presence of strong organic bases; an improved procedure for the synthesis of vinyl iodides and phenyl-vinyl selenides

The oxidation of hydrazones by iodine in the presence of strong organic bases (guanidines) has been studied. Improved yields of vinyl iodides can be obtained by inverse addition using dry solvents and with a final heating period where appropriate. The reaction has been extended to various dihydrazones with interesting results.In complementary studies hydrazones have been oxidized by phenylselenenyl bromide in the presence of strong organic bases to give the corresponding phenyl vinyl selenides in good yield.     

Through space spin-spin coupling <Superscript>19</Superscript>F-<Superscript>1</Superscript>H as the base for comparative analysis of conformational equilibrium in fluorine-substituted aryl vinyl selenides and sulfides

The analysis of long-range spin-spin coupling ¹⁹F-¹H and the other conformation-dependent parameters of ¹H NMR spectra shows that aryl vinyl selenides like aryl vinyl sulfides exist as mixtures of s-cis and s-trans rotational isomers. The combined data of ¹H and ¹³C NMR spectra reveal the increase in the torsional angle ϑ at the bond X-CH=CH₂ (X = S, Se) in selenides compared to sulfides due to diminished interaction energy of the unshared electron pairs of selenium with the π*-orbitals of the double bond as compared to analogous interaction in sulfides.     

Glycerol as a promoting medium for cross-coupling reactions of diaryl diselenides with vinyl bromides

We described herein the use of glycerol as a novel solvent in the cross-coupling reaction of diaryl diselenides with vinyl bromides catalyzed by CuI. This cross-coupling reaction was performed with diaryl diselenides and (Z)- or (E)-vinyl bromides bearing electron-withdrawing and electron-donating groups, affording the corresponding vinyl selenides in good to excellent yields. The mixture glycerol/catalyst can be directly reused for further cross-coupling reactions.     

Indium(I) iodide promoted cleavage of diphenyl diselenide and disulfide and subsequent palladium(0)-catalyzed condensation with vinylic bromides. A simple one-pot synthesis of vinylic selenides and sulfides

[reaction: see text] Diphenyl diselenide (and disulfide) undergo facile reaction with indium(I) iodide and the corresponding intermediate complex condenses in situ with a variety of substituted vinyl bromides in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium(0) [Pd(PPh3)4] in THF at room temperature to produce vinylic selenides and sulfides in good yields. The conversion of (E)-vinyl bromides is remarkably stereoselective giving (E)-vinyl selenides (and sulpfides) whereas the stereoselectivity in reaction of (Z)-vinyl bromides is not very good.     

Hydroselenation of alkynes using NaBH4/BMIMBF4: easy access to vinyl selenides

A general and easy method for the synthesis of several vinyl selenides using NaBH₄ and BMIMBF₄ as a recyclable solvent is described. This efficient and improved method furnishes the corresponding vinyl chalcogenides preferentially with Z configuration. We also observed that when the same protocol was applied to phenyl acetylene, (E)-bis-phenylseleno styrene was obtained in good yield and with high selectivity.     

Synthesis of tris(organylthioethyl)phosphines and their derivatives on the basis of the reaction of phosphine with vinyl sulfides

Phosphine generated from the red phosphorus in the system KOH-H₂O-toluene adds regio- and chemoselectively to vinyl sulfides under radical initiation conditions with the formation of tris(2-organylthioethyl)phosphines, which are easily oxidized by elemental sulfur and selenium to the corresponding phosphine sulfides and phosphine selenides in 54–78% yield. The obtained adducts are split when treated with sodium amide in THF to give trivinylphosphine and trivinylphosphine chalcogenides.     

Reaction of Vinyl Selenides with Secondary Phosphines and Elemental Selenium: One‐Pot Selective Synthesis of a New Family of Diselenophosphinic Se‐Esters

Alkyl vinyl selenides react with diverse secondary phosphines and elemental selenium in a 1.1:1:2 molar ratio (120–124°C, 20–40 min, 1,4‐dioxane) to afford selectively earlier unknown diselenophosphinic Se‐esters, R₂P(Se)SeCH(Me)SeR´, in 82–99% yield. This three‐component atom‐economic reaction proceeds via intermediate formation of diselenophosphinic acid R₂P(Se)SeH (generated from secondary phosphine and selenium), which adds to the double bond of vinyl selenide in a Markovnikov manner to give the target products.     

Transition-metal free synthesis of diaryl vinyl selenides: a simple synthetic approach with high selectivity

A simple, highly efficient synthetic protocol is developed for the synthesis of unsymmetrical diaryl vinyl selenides from diaryldiselenide and β-bromo styrene under transition-metal free conditions in N,N′-dimethyl propylene urea and 130 °C to afford high yields and excellent selectivities. This method provides a new strategy to fabricate a wide variety of important substituted molecular skeletons and an alternative to conventionally used metal salts, additives, and ligands.     

Enantioselective synthesis of α-alkyl,α-vinyl amino acids via [2,3]-sigmatropic rearrangement of selenimides

Chiral α-alkyl,α-vinyl amino acids (quaternary vinyl glycine derivatives) are prepared with high levels of enantiomeric purity by [2,3]-sigmatropic rearrangement of allylic selenimides. The required trisubstituted allylic selenides are prepared by an organocatalytic α-selenenylation of aldehydes followed by Horner-Wadsworth-Emmons (HWE) olefination. Both (E)-and (Z)-geometrical isomers are available giving access to both enantiomers of the desired products.     

Regioselective Addition of Dithiophosphinic Acids to Vinyl Sulfides and Selenides: An Efficient Route Toward Functional Dithiophosphinates

Earlier unknown S‐[1‐(organosulfanyl)ethyl]‐ and S‐[1‐(organoselenyl)ethyl] dithiophosphinates were synthesized in 85–97% yields by regioselective addition of dithiophosphinic acids to diverse vinyl sulfides and selenides under mild conditions (ambient temperature, Et₂O, 3 h).