A. G. Khabibulina

Reaction of selenium dichloride with acrylic acid and its derivatives. Regioselective synthesis of new functionalized selenides

Selenium dichloride reacted with acrylic acid, ethyl acrylate, and acrylonitrile at −20°C in a regionselective fashion to give the corresponding anti-Markovnikov adducts. This reaction was used as a basis to develop an efficient procedure for the synthesis of new functionalized selenides in nearly quantitative yields. Raising the temperature to −10°C or ambient led to loss of regioselectivity and formation of mixtures of addition products at both α- and β-positions of the double bond.

Stereoselective synthesis of Z-2-bromo-2-phenylvinyltellurium tribromide and Z,Z-bis(2-bromo-2-phenylvinyl)ditelluride

Reactions of alkynes with tellurium tetrachloride have been reported [1, 5–11]. However, there are a few published data on reactions of tellurium tetrabromide with acetylenes [12–14]. We have developed efficient procedures for the stereoselective synthesis of E,E-bis(2-bromovinyl)tellurium dibromide and E-(2-bromovinyl)tellurium tribromide by reaction of tellurium tetrabromide with acetylene [12, 13]. The addition of TeBr4 to phenylacetylene and hept-1-yne under reflux gives rise to bis-adducts, bis(2-bromo-2-phenylvinyl)tellurium dibromide and bis(2-bromohept-1-en-1-yl)tellurium dibromide in 89 and 70% yield, respectively, as mixtures of Z and E isomers with Z-isomers pre-vailing (in the case of phenylacetylene Z : E = 4.5 : 1) [14]. The data on stereoselective synthesis of monoadduct, 2bromo-2-phenylvinyltellurium tribromide, are absent.

Regio- and stereoselective addition of tellurium tetrachloride to methyl propargyl ether

Reaction of tellurium tetrachloride with methyl propargyl ether proceeds regio- and stereoselectively to afford a product of anti-addition against the Markovnikoff’s rule in quantitative yield. The obtained compound was reduced by sodium metabisulfite into E,E-bis(3-methoxy-1-chloroprop-1-en-2-yl)ditellane.

Reactions of selenium dihalides with vinylbenzenes

Alkoxyselenation of vinylbenzenes with selenium dihalides was accomplished for the first time. The reaction with selenium dibromide was the most efficient. Selenium dibromide reacted with vinylbenzene and 1-chloro-4-(prop-1-en-2-yl)benzene in chloroform or methylene chloride in the presence of methanol or ethanol to give the corresponding Markovnikov adducts, bis(2-alkoxy-2-phenylethyl) selenides and bis[2-alkoxy-2-(4-chlorophenyl)propyl] selenides in 82–95% yield with high regioselectivity. Bis(2-halo-2-phenylethyl) selenides can be obtained at low temperature (–60°C).

Reaction of selenium dichloride with methacrylic acid

Selenium dichloride and dibromide in solution undergo disproportionation, so that they could not be isolated as individual substances [1]. Freshly prepared (in situ) selenium dichloride and dibromide are effective electrophilic reagents which are immediately involved in various transformations leading to organoselenium compounds [2–6]. We perform systematic studies on reactions of selenium dichloride and dibromide with compounds containing a double bond [3–5]. Reactions of selenium dihalides with divinyl sulfide [3] and divinyl selenide [4] give the corresponding Markovnikov addition products, 2,6-dihalo-1,4-thiaselenanes and -diselenanes, which undergo rearrangement into thermodynamically more stable 1,3-thiaselenolanes and -diselenolanes. Unlike vinyl sulfides and vinyl selenides, the double bond in vinyl sulfones is deactivated toward addition of electrophiles due to strong electron-withdrawing effect of the sulfonyl group. Selenium dihalides react with divinyl sulfone at a much lower rate as compared to divinyl sulfide, leading to fourand fivemembered heterocycles [6]. Methacrylic acid is a compound whose molecule contains a double bond and a strong electron-withdrawing group. Reactions of selenium halides with methacrylic acid were not studied. We examined the reaction of selenium dichloride with methacrylic acid at a molar ratio of 1 : 2 in acetonitrile at room temperature. Instead of expected 1 : 2 adduct we isolated in high yield (92%) a compound containing a diselenide moiety, previously unknown 2,2′-diselanediylbis(3-chloro-2-methylpropanoic acid) (I), whereas no analogous monoselenide was detected. Diselenide I was also obtained when Se2Cl2 was used instead of SeCl2; in this case, the reaction was accompanied by liberation of an equimolar amount of elemental selenium. The structure of diselenide I was confirmed by the H, C, and Se NMR and mass spectra and elemental analysis. It was isolated as two diastereoisomers at a ratio of 8 : 1. The observed coupling constant between the selenium atom and quaternary carbon atom (JSeC = 77 Hz for the major diastereoisomer) corresponds to direct coupling (JCSe) [7]. Thus the reaction of selenium dichloride with methacrylic acid is chemo-, regio-, and stereoselective, and it leads to the formation of diselenide I. Probable mechanism of this transformation is now under study. 2,2′-Diselanediylbis(3-chloro-2-methylpropanoic acid) (I). White powder, mp 121–122°C. H NMR spectrum, δ, ppm: major diastereoisomer: 1.52 s (6H, CH3), 3.85 d and 4.14 d (2H each, CH2Cl, J = 10.6 Hz); minor diastereoisomer: 1.53 s (6H, CH3), 3.81 d and 4.11 d (2H each, CH2Cl, J = 10.6 Hz). C NMR spectrum, δC, ppm: major diastereoisomer: 20.74 (CH3, JSeC = 16.2 Hz), 49.11 (CCH3, JCSe = 77 Hz), 51.29 (CH2Cl, JSeC = 15.1 Hz), 172.21 (C=O); minor diastereoisomer: 20.65 (CH3), 49.21 (CCH3), 51.29 (CH2Cl), 172.05 (C=O). Se NMR spectrum: major diastereoisomer: δSe 545 ppm; minor diastereoisomer: δSe 544 ppm. Mass spectrum (electron impact, 70 eV), m/z (Irel, %): 402 (4) [M] , 236 (10), 200 (7), ISSN 1070-4280, Russian Journal of Organic Chemistry, 2011, Vol. 47, No. 12, pp. 1889–1890.

Synthesis of Fused Compounds on the Basis of Chalcogen Chlorides and 2-Allylphenols

Efficient methods have been developed for regioselective synthesis of new organochalcogen compounds containing 2,3-dihydro-1-benzofuran-2-ylmethyl and 7-methyl-2,3-dihydro-1-benzofuran-2-ylmethyl substituents by reactions of selenium and sulfur dichlorides and tellurium tetrachloride with 2-allylphenol and 2-allyl-6-methylphenol.

Alkoxytelluration of Allylbenzene

Abstract(2-Alkoxy-3-phenylpropyl)trichlorotellanes were synthesized by regioselective reaction of tellurium tetrachloride with allylbenzene in the system MeOH–CH2Cl2, as well as by nucleophilic substitution of chlorine in trichloro(2-chloro-3-phenylpropyl)tellane in MeOH–CH2Cl2 and EtOH–CHCl3. Allylbenzene reacted with tellurium tetrabromide on heating in methanol or ethanol. The reduction of (2-alkoxy-3-phenylpropyl) trihalotellanes with NaBH4 in H2O–THF gave 1,2-bis(2-alkoxy-3-phenylpropyl)ditellanes.

Synthesis of bis(2-haloalkyl) selanes and selenides based on selenium dioxide and terminal alkenes

Selenium tetrahalides generated from selenium dioxide and hydrogen halides (HCl, HBr) reacted with hex-1-ene, hept-1-ene, and oct-1-ene at a SeO2‒alkene molar ratio of 1: 2 to give mixtures of dihalobis-(2-haloalkyl)-λ4-selanes (yield 80‒90%) and bis(2-haloalkyl) selenides (yield 5‒12%). Halogenation of the resulting mixtures afforded 85‒93% (calculated on the initial SeO2) of the corresponding dihalobis(2-haloalkyl)-λ4-selanes, and the reduction of the same mixtures with Na2S2O5 gave bis(2-haloalkyl) selenides in 80‒86% yield. In the reaction with a SeO2‒alkene ratio of 5: 8, pure dihalobis(2-haloalkyl)-λ4-selanes were formed in 84‒93% yield. Dichlorobis(2-chloro-2-phenylethyl)-λ4-selane was obtained in 72% yield in the reaction of SeO2‒HCl with styrene.

Stereoselective synthesis of ( Z , E )-bis(2-chloroethenyl)tellanes

A procedure for the stereoselective synthesis of dichloro[(Z)-2-chloro-2-phenylethenyl][(4E)-5- chlorooct-4-en-4-yl]-λ4-tellane and [(Z)-2-chloro-2-phenylethenyl][(4E)-5-chlorooct-4-en-4-yl]tellane has been developed on the basis of anti-addition of tellurium tetrachloride–phenylacetylene monoadduct to oct-4-yne.

Efficient methods of synthesis of unsaturated alcohols and ketones by allylation of Favorsky reaction products under phase transfer conditions

Allylation of the Favorsky reaction products with allyl halides under phase-transfer catalysis in the system CuI–K2CO3–Na2SO3–BTEAC–H2O–C6H6 afforded the corresponding allylpropargyl alcohols in high yields (87–96%). The procedure is practical and scalable (more than 50 g of the target product can be prepared in a single run) and is characterized by high selectivity. Oxidation of secondary allylpropargyl alcohols with manganese dioxide in anhydrous acetonitrile at room temperature gave 75–81% of allylacetylenic ketones.