Robert D. Chapman
Phillips Laboratory
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Featured researches published by Robert D. Chapman.
Journal of Fluorine Chemistry | 1995
Dale F. Shellhamer; Michael Chua Chiaco; Kelly M. Gallego; William S.C. Low; Barbara Carter; Victor L. Heasley; Robert D. Chapman
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.
Journal of The Chemical Society-perkin Transactions 1 | 1991
Dale F. Shellhamer; David L. Carter; Michael Chua Chiaco; Tyler E. Harris; Rodney D. Henderson; William S.C. Low; Brett T. Metcalf; Michael C. Willis; Victor L. Heasley; Robert D. Chapman
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.
Journal of The Chemical Society-perkin Transactions 1 | 1997
Melvin L. Druelinger; Dale F. Shellhamer; Robert D. Chapman; Scott A. Shackelford; Maurice E. Riner; Steven L. Carter; Ryan P. Callahan; Cameron R. Youngstrom
The electrophilic reactivity of proposed alkoxyxenon fluoride (ROXeF) nintermediates based on electronegatively substituted (polyfluorinated nand polynitroaliphatic) alcohols has been characterized with model nalkenes norbornene, 2-methylpent-1-ene and hex-1-ene. The alkoxyxenon nfluorides can react as positive oxygen electrophiles—initially nincorporating alkoxy substituents—or as apparent fluorine nelectrophiles—resulting in initial fluorine nincorporation—depending on conditions. Efficient simple addition nof poorly nucleophilic alcohols to norbornene was observed in certain nsystems. Selectivity between the various reaction paths (simple nfluorination, alkoxyfluorination or alcohol addition) was observed to be na sensitive function of various reaction conditions, especially solvent, ntemperature and catalyst.
Polymer Bulletin | 1992
Jeffrey W. Gilman; Yoshiko A. Otonari; Robert D. Chapman
SummaryTwo triisocyanate crosslinking agents were synthesized. The 2,2-bis(isocyanatomethyl)-propyl isocyanate was synthesized from 2,2-bis(hydroxymethyl)propanol in three steps via the triazide and the triamine with an overall yield of 20% and >95% purity as determined by NMR. The 4-(isocyanatomethyl)-1,7-heptyl diisocyanate was synthesized from 1,3,5-pentanetricarboxylic acid in six steps with an overall yield of 23.5% and >98% purity as determined by NMR. This synthesis proceeded via the trimethyl ester, the triol, the tris(p-toluenesulfonate), the triazide and the triamine.
Journal of The Chemical Society-perkin Transactions 1 | 1989
Dale F. Shellhamer; Steven L. Carter; Robert H. Dunham; Stuart N. Graham; Mark P. Spitsbergen; Victor L. Heasley; Robert D. Chapman; Melvin L. Druelinger
Xenon difluoride (XeF2) reacts with alcohols to form unstable alkoxyxenon fluoride intermediates (ROXeF). The regio- and stereo-chemistry of products from reaction of ROXeF with indene were determined. Alkoxyxenon fluorides [R = CH3, (CH3)2CH, and (CH3)3C] react as positive oxygen electrophiles (OE) when boron trifluoride–ether is used as catalyst. However, these alkoxyxenon fluorides react as apparent fluorine electrophiles (FE) with proton catalyst (hydrogen fluoride generated in situ). Reactions of XeF2 and alcohols with electron-withdrawing substituents give alkoxyxenon fluorides which add to indene as an OE species even though boron trifluoride–ether was not used as catalyst. Reactions of XeF2 with polynitroaliphatic alcohols and indene give rapid polymerization of indene rather than alkoxyfIuorination.
Journal of Fluorine Chemistry | 1985
Dale F. Shellhamer; S.N. Graham; S.L. Carter; S.A. Shackelford; Robert D. Chapman
Abstract Xenon difluoride reacts with methanol to form the unstable reactive species methoxyxenon fluoride ( 1 ). In the absence of unsaturated hydrocarbons, this specie quantitatively disproportionates to formaldehyde and hydrogen fluoride; however, in the presence of alkene substrates a competitive methoxyfluorination reaction results. During methoxyfluorination, the highly reactive intermediate ( 1 ) displays a novel ambivalent addition character depending upon whether catalysis is accomplished by protonic acids (H2SO4 & HF generated in-situ ) or Lewis acid species (BF3 & BF3 etherate). Catalysis with protonic acids produces an apparent fluorine electrophilic intermediate ( 2 ) where fluorine adds first and results in Markownikoff fluoromethoxy products predominating. Reaction in the presence of Lewis acids provides a positive oxygen electrophile as intermediate ( 3 ) where the methoxy group adds first and produces mainly anti -Markownikoff fluoromethoxy products. The reaction mechanism involving species 1 , 2 , and 3 were studied by using five alkenes with varying structural features; in the case of the very electron rich alkene dihydropyran, reaction with XeF2 occurred before 1 could form. Current mechanistic studies of this alkoxyfluorination reaction involve varying the alcoholic substrate with electron-donating and electron-withdrawing alkoxy moieties.
Journal of Fluorine Chemistry | 1985
S.A. Shackelford; Robert D. Chapman; J.L. Andreshak; S.P. Herrlinger; R.A. Hildreth; J.C. Smith
Abstract When reacted with the silver triflate reagent, lower α , w -dibromoalkanes in the 1,2-dibromoethane homologous series display a unique reaction stability and product selectively over their higher homologues and corresponding primary monobromoalkanes. Often monobromoalkanes and α , w -dibromoalkanes greater than 1,4-dibromobutane undergo alkylation in benzene solvent and polymerize in CCl4; but the lower 1,2- through 1,4-dibromoalkanes produce desired monobromotriflate and ditriflate products. These same lower α , w -dibromoalkanes also resist product Brue5f8(CH2)nue5f8Br + xAgOTf→TfOue5f8(CH2)nue5f8Br + TfOue5f8(CH2)nue5f8OTf + xAgBr↓ rearrangement to 2°-triflate products while the higher homologues and 1°-monobromoalkanes do not. The 1,2- through 1,4-dibromoalkanes potentially offer a selective synthesis route to key difunctional derivatives through sequential metathesis. The unique stability and selectivity of the lower homologous are best explained by bromonium ion anchmeric assistance in the first metatheis step followed by a rare example of cyclic triflate group anchimeric stabilization. This subject reaction offers distinct synthetic advantages but is very susceptible to several reaction parameters. These parameters and the potential synthetic advantages of this reaction system will be discussed.
Synthesis | 1997
Dale F. Shellhamer; Ryan P. Callahan; Victor L. Heasley; Melvin L. Druelinger; Robert D. Chapman
Journal of Organic Chemistry | 1986
Robert D. Chapman; John L. Andreshak; Stephen P. Herrlinger; Scott A. Shackelford; Robert A. Hildreth; Jeffrey P. Smith
Journal of Organic Chemistry | 1988
Robert D. Chapman; John L. Andreshak; Scott A. Shackelford