Victor L. 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.

A mild method for introducing iodine monofluoride into alkenes and iodination of aromatics using xenon difluoride

Abstract Reaction of xenon difluoride (XeF 2 ) and iodine (I 2 ) or N -iodosuccinimide (NIS) with alkenes gives iodofluoro products in good yields. Aromatics react with XeF 2 and I 2 or NIS to undergo electrophilic aromatic iodination. Iodine monofluoride (IF) generated from XeF 2 is less reactive than IF generated from I 2 and fluorine gas. This difference in reactivity suggests that the interhalogen IF is delivered to the alkene or aromatic from a complex with XeF 2 .

Reaction of alkylhypochlorites and xenon difluoride with cyclohexene

Abstract Reactions of alkylhypochlorites and xenon difluoride with cyclohexene give primarily 1-chloro-2-fluorocyclohexanes via formation of a complex between xenon difluoride and the alkylhypochlorite.

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.

Reaction of Chlorosulfonyl Isocyanate with Fluorosubstituted Alkenes: Evidence of a Concerted Pathway

Concerted reactions are indicated for the electrophilic addition of chlorosulfonyl isocyanate with monofluoroalkenes. A vinyl fluorine atom on an alkene raises the energy of a stepwise transition state more than the energy of the competing concerted pathway. This energy shift induces CSI to react with monofluoroalkenes by a one-step process. The low reactivity of CSI with monofluoroalkenes, stereospecific reactions, the absence of 2:1 uracil products with neat fluoroalkenes, and quantum chemical calculations support a concerted pathway.

Comparison of the electrophilic and free-radical addition of halogens with hexafluoro-1,3-butadiene and 1,3-butadiene

Abstract Ionic and photochemical reaction of chlorine (Cl2), bromine (Br2) and iodine monochloride (ICl) to hexafluoro-1,3-butadiene (1) and 1,3-butadiene (2) were carried out under conditions that would provide product distributions under controlled ionic or free-radical conditions. Product distributions for ionic reaction of Cl2 and Br2 with 1 are similar and suggest a weakly-bridged halonium ion species. Theoretical calculations support weakly-bridged chloronium and bromonium ions for both dienes 1 and 2. There are more of the 1,4-dihalo-2-butene products from ionic halogenation of 1 than 2 which correlates with the greater charge density on carbon-4 of halonium ions from 1. Ionic and free-radical reactions of ICl with 1 give 8 and 2% of 3-chloro-4-iodohexafluoro-1-butene and 4-chloro-3-iodohexafluoro-1-butene, respectively. The minor cis-1,4-dihalo-2-butene products from 1 and 2 are reported when formed.

The fluorination of cyclopentadiene and 3,4-epoxycyclopentene

Abstract Cyclopentadiene (1) was treated with xenon difluoride and (difluoroiodo)benzene to give trans - and cis -3,4-difluorocyclopentenes (2,3) and trans - and cis -1,4-difluorocyclopentenes (4,5). Reaction of 3,4-epoxycyclopentene (6) with pyridinium polyhydrogen fluoride gave four fluorohydrins which were converted with diethyiaminosulfur trifluoride (DAST) to the difluorocyclopentenes 2-5. The best yield (50%) of the difluorocyclopentenes was from the reaction of DAST with epoxide 6. Synthesis and isolation of these labile difluorides of cyclopentenes (2-5) demonstrate the mild nature of these fluorinating reagents.

Rearrangement of 3-membered 1,1,2-trifluorobromonium and iodonium ions and comparison of trifluorochloronium to fluorocarbenium ions.

Reactions of chlorine (Cl(2)) with 4-halo-1,1,2-trifluorobut-1-enes (1, 2, or 3) give open-ion intermediates A and E that are in equilibrium. The open-chloronium ions (E) rearrange to a five-membered-ring halonium ion during ionic chlorination of 3 when the number-4 halo-substituent is iodine. Three-membered-ring bromonium and iodonium ions from alkenes 1, 2, or 3 are rather symmetrical and similar in structure. Quantum chemical calculations show that five-membered-ring halonium ion intermediates are 11 to 27 kcal/mol more stable than the three-membered-ring halonium ions or the open-ions A and E. The five-membered-ring intermediates lead to rearranged products. Rearranged products increase as the number-4 halogen (Z) becomes more nucleophilic (Z: Cl < Br < I). Open chloronium ions from ionic chlorination of terminal fluorovinyl alkenes are compared to the open ions generated by protons to similar alkenes.