V. R. Kartashov

Trans-acetoxymercuration of diphenylacetylene

Abstract In contrast with literature data, the acetoxymercuration of diphenylacetylene proceeds to give trans -adduct, 2, the configuration of which was established on the basis of 13 C, 199Hg NMR and X-ray data.

Kinetics and mechanism of the doping-addition of Arscl to olefins

Abstract A lithium percholate effect on the rate and product ratio of 2,4-dinitrobenzenesulfenyl chloride doping-addition to 1-methylcyclopropene ( 5 ) and tetrafluorobenzobarrelene ( 10 ) in acetic acid has been examined. The rates of both doping-addition reactions follow the normal salt effect dependence. However, the yields of doping-addition products is much higher than expected from the term k o .b.[LiClO 4 ] at low concentrations of the salt added and, hence, the catalytic influence of LiClO 4 on product formation is much more pronounced than expected from normal salt effect dependence. The mechanism of doping-addition is analyzed in detail.

Stereochemistry of addition of mercury salts to alkynes

Reactions of Hg(OOCR)2 (R=Et, Prn, Pri, and Bun) with methylphenylacetylene (with the corresponding acids as solvents) give mixtures ofcis- andtrans-adducts. The quantity of thecis-adduct increases with increase in the length of the acyl substituent.syn-Addition also occurs in the acetoxymercuration ofm-chlorophenyl(methyl)acetylene and 1-methoxybut-2-yne; in the latter case, this route predominates. The stereochemistry of the reaction can also depend on the ratio of the reactants. It is proposed that the reaction occurs by several schemes in which these factors manifest themselves in different degrees.

The common ion effect in sulfenylhalogenation of alkenes in formic acid

The reactions of 2,4-dinitrobenzenesulfenyl chloride with cyclohexene and allylbenzene in formic acid were studied. In this solvent, the reaction yields solvo-adducts and the products of addition of the reagent to the double bond. The reaction follows kinetics of the second order, first order with respect to each reagent. The hydrogen chloride evolved in the reaction has no effect on the overall rate of the process but sharply decreases the rate of accumulation of solvo-adducts due to the common ion effect. In the reaction with allylbenzene, the yield of the solvo-adduct can vary under the action of HCl from 88% at low degrees of reagent conversion to 30% when the reaction is complete.

Salt effects and the mechanism of electrophilic mercuration of unsaturated compounds

The kinetics of the addition of Hg(OAc)2 to strained and unstrained alkenes was studied in MeOH solution in the presence of NaOAc. Based on salt effects, the HgOAc ion was shown to be the actual reagent in the reaction of the unstrained alkenes, whereas Hg(OAc)2 was the reagent in the case of the strained alkenes. The mechanisms of the solvomercuration of alkenes of various structures were proposed.

Salt effects in the mercuration of unsaturated compounds. Kinetic evidence for the formation of ion pairs and a solvated ion

The kinetics of mercuration of bornylene and cyclohexene in different solvents in the presence of NaOAc and LiClO4 has been investigated. Addition of NaOAc sharply decreases the rate of addition reactions of mercuric acetate to bornylene and cyclohexene in alcohols; the main direction of the mercuration of bornylene is the formation of acetoxy-adducts, and the yield of solvo-adducts decreases from 76 % in the absence of NaOAc, to 19 % in the presence of the salt (4·10−3 mol L−1). A reaction scheme involving the participation of intermediate ion pairs and a solvated mercurinium ion is suggested and confirmed by a steady-state concentration method. The influence of NaOAc on the rate of the reaction and on product formation is realized through the common ion effect.

REGIOCHEMISTRY OF THE ADDITION OF MERCURY SALTS TO BORNYLENE

The dependence of the regiochemistry of the mercuration of bornylene on the nature of the mercurating reagent and on the solvent has been found. The structures of the intermediate and transition state in these reactions have been proposed.

Reactions of mercury salts with benzo- and tetrafluorobenzobarrelenes

Regiochemistry and stereochemistry of the addition of mercury salts to benzobarrelene and tetrafluorobenzobarrelene have been studied in acetic acid and methanol. The effect of the substrate structure on the regiochemistry of the reaction is discussed.

Stereoselectivity of the reaction of mercuric acetate with dimethyl bicyclo[2.2.2]oct-2-en-5,6-cis-endo-dicarboxylate

The stereoselelectivity of the reaction of mercuric acetate with dimethyl bicyclo[2.2.2]oct-2-en-5, 6-cis-endo-carboxylate in acetic acid was studied. One of the reaction products is formed when the reagent attacks the double bond from the sterically less accessible side. The nature of the orientation effect of the carboxylate groups is discussed.

The reaction of mercuric salts with dimethyl bicyclo[2.2.2]octa-2,5-diene-5,6-dicarboxylate

The regioselectivity and stereochemistry of the reaction of mercuric salts with dimethyl bicyclo[2.2.2.]octa-2,5-diene-5,6-dicarboxylate were studied in different solvents. The factors determining the reaction regioselectivity were considered.