Gene E. Heasley

Boron trifluoride promoted reactions of n-haloelectrophiles with alkenes

Abstract N-Haloelectrophiles react with alkenes in the presence of boron rifluoride etherate to give halofluorides and N-halo adducts.

Reaction of halogens with some α,β-unsaturated aldehydes and ketones

Abstract Mechanisms are proposed to account for evidence indicating that some simple α,β-unsaturated aldehydes and ketones do not react with halogens by the expected attack on the CC bond.

Radical additions of xenon difluoride to cis- and trans-1-phenylpropenes: comparison with trichloramine and iodobenzene dichloride

Abstract We would like to report data which support a free radical pathway for reaction of xenon difluoride (XeF 2 ) with alkenes in organic solvent. Radical intermediates have been proposed for reaction of XeF 2 to double bonds. For example, a radical pathway was suggested for the gas phase reaction of XeF 2 to ethylene and propene [1]. Zupan speculated on a radical cation pathway for the acid catalyzed reaction of XeF 2 with alkenes but gave no experimental evidence for this mechanism [2,3]. Radical cation intermediates were demonstrated for the reaction of XeF 2 to aromatics by Filler [4]. Acid catalyzed ionic reactions to unsaturated hydrocarbons have been reviewed [5]. Zupan and Pollak have shown that alkenes do not react in aprotic solvent with XeF 2 at low concentrations of alkene unless acid catalyst is present [3]. However, we observed that illumination of a dilute solution of cis- or trans -1-phenylpropenes (I) or (II) in methylene chloride at 0° with a 270 watt sunlamp produced IIIa and IIIb in less then two hours (Table). Furthermore, at high concentration of (I) and (II), a spontaneous reaction occurred in the dark between XeF 2 and these styrenes. The reaction conditions for both of these reactions imply a radical mechanism — the latter a molecule-induced pathway.

Reaction of methyl hypochlorite with certain olefins in the presence of boron trifluoride

Abstract Fluoro chlorides are major products in the reaction of methyl hypochlorite with certain olefins in the presence of boron trifluoride.

Evidence for the existence of methyl hypofluorite: methanolysis of xenon difluoride

Abstract Methyl hypofluorite is indicated as an intermediate in the reaction of xenon difluoride with alkenes in methanol as solvent.

Chlorination of α,β-unsaturated ketones and esters in the presence of acid scavengers

The chlorination of a series of α,β-unsaturated ketones and esters by Cl2 in CH3OH, with and without acid scavengers such as N-chlorosuccinimide (NCS), pyridine and 2,6-lutidine, is described. Methyl vinyl ketone and cyclohex-2-enone have also been chlorinated in ethanol. Mixtures of Markovnikov(M) and anti-Markovnikov(AM) methoxy chlorides and dichlorides are formed in most cases; phenyl vinyl ketone gives no M products in the absence of pyridine, M methoxy chloride is not formed with (E-)-4-chlorobut-3-en-2-one under any conditions, pyridine has no effect on the product ratios and methyl 3-chlorobut-2-enoate forms only dichloride. Chlorination of the ketones in the presence of the pyridines results in a significant increase in the M regioisomer (except for methyl isopropenyl ketone and the ketones mentioned), giving M:AM ratios which are similar to the corresponding esters. Ratios for the esters are not affected significantly by pyridine. We ascribe the effect of the pyridine bases to the elimination of acid and the acid-catalysed mechanism, permitting the chlorination to occur via a carbon–carbon π-bond (chloronium ion) mechanism. The rate of chlorination of methyl vinyl ketone is retarded by pyridine but is still considerably faster than methyl acrylate. NCS, in contrast to N-bromosuccinimide (NBS) reported previously, has no effect on the M:AM ratio. The chlorination of methyl vinyl ketone with NCS and HCl gives markedly different results from Cl2.

Borate promoted electrophilic additions of alkyl hypohalites

Abstract Catalysis by trimethyl borate promotes a rapid ionic reaction of methyl hypobromite with alkenes and dienes in methylene chloride.

Addition of halogens to 3-fluoro-1-hexyne

Abstract A few years ago we reported on the addition of bromine chloride (BrCl) to 1-hexene and 1-hexyne. 1-hexyne reacts with BrCl to give Markownikoff and anti -Markownikoff projects 1a and 2a in a 90:10 ratio respectively. Reaction of 3-fluoro-1-hexyne with bromine and chlorine give cis - and trans -1,2-dihalo-1-hexenes. Addition of BrCl to 3-fluoro-1-hexyne gives a major project which is tentatively assigned the structure 2b . Thus reaction of BrCl with 1-hexyne and 3-fluoro-1-hexyne give intermediates 3 and 4 respectively. A possible free radical process or radical competing pathway for the reactions of halogens with 3-fluoro-1-hexyne is also considered.