Dale F. Shellhamer

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.

Chlorination of 1-hexyne and 3-hexyne in acetic acid and methanol

Chloration par Cl 2 ou Cl 2 -LiCl dans lacide acetique, le methanol ou le dichloromethane. Formation de dichlorohexenes, dichlorohexanones, de chloroacetate de (chloro-2 ethyl-1) butene-1yle

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.

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.

Reaction of diethylaminosulfur trifluoride with diols

Diethylaminosulfur trifluoride (DAST) reacts with dialcohols to give difluorides, sulfite esters or cyclic ethers depending on the number of carbons separating the two alcohol groups. Vicinal and 1,3-diols give large amounts of sulfite ester products while butane-1,4-diol gives almost exclusively the cyclic ether tetrahydrofuran. Terminal dialcohols longer than four carbons give primarily difluoride products. Semiempirical calculations indicate a preference for cyclic intermediates when four or less carbons separate the two alcohol moieties. These cyclic intermediates lead directly to the cyclic ethers and sulfite ester products.

Reaction of xenon difluoride with indene in aqueous 1,2-dimethoxyethane and tetrahydrofuran

Xenon difluoride (XeF2) reacts with indene in 1,2-dimethoxyethane–water (90:10) to give cis- and trans-2-fluoro-1-hydroxyindans. Our data indicate that neither xenon oxide (XeO) nor hydroxyxenon fluoride (HOXeF) is an intermediate in this reaction even though XeO is a suspected intermediate from aqueous hydrolysis of XeF2.

Benchtop synthesis and characterization of air-stable titanocene(IV) complexes from phosphorous- and sulfur-based amino acid analogs

Four new air-stable titanocene(IV) salt complexes were synthesized by reacting titanocene dichloride with phosphorous- and sulfur-based β-amino acid analogs in standard chemical glassware open to atmospheric conditions. Each new titanocene(IV) complex contained two identical ligands with a terminal ammonium chloride group and either the phosphorous- or sulfur-based ester group bonded directly to the central titanium atom. Each complex was characterized by 1H, 13C, and 31P NMR, IR, UV, and MS analyses. Initial data revealed the titanocene(IV) complexes with sulfonate or sulfate amino ester ligands to be far more stable to hydrolysis than the analogous phosphonate or phosphate amino ester complexes.

Reaction of aminosulfur trifluorides with alcohols: inversion vs. retention

Reaction of aminosulfur trifluorides with alcohols replaces the hydroxy group with fluorine. A study with the cyclic secondary alcohols trans-2-bromoindan-1-ol (3), trans-2-methylcyclopentanol (7), cis-2-methylcyclopentanol (8), trans-[2-2H1]cyclopentanol (9), cis-[2-2H1]cyclopentanol (10) and trans-2-fluorocyclopentanol (11) gave primarily inversion of configuration via an SN1-like pathway. The product stereochemistry and alkene formation in the reaction of aminosulfur trifluorides with cyclopentanols was similar to the products of solvolysis of cyclopentyl tosylates in methanol. The stereochemistry of the fluoro products was confirmed by independent synthesis or assigned by 1H and 19F NMR spectral data except for the deuteriated products 14 and 15 whose stereochemistry was assigned by their 2H NMR data.