- Bare-minimum fluorous mixture synthesis of a stereoisomer library of 4,8,12-trimethylnonadecanols and predictions of NMR spectra of saturated oligoisoprenoid stereoisomers
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All four diastereomers of a typical saturated oligoisoprenoid, 4,8,12-trimethylnonadecanol, are made by an iterative three-step cycle with the aid of traceless thionocarbonate fluorous tags to encode configurations. The tags have a minimum number of total fluorine atoms, starting at zero and increasing in increments of one. With suitable acquisition and data processing, each diastereomer exhibits characteristic chemical shifts of methyl resonances in its 1H and 13C NMR spectra. Together, these shifts provide a basis to predict the appearance of the methyl region of the spectrum of every stereoisomer of higher saturated oligoisoprenoids.
- Yeh, Edmund A.-H.,Kumli, Eveline,Damodaran, Krishnan,Curran, Dennis P.
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supporting information
p. 1577 - 1584
(2013/03/28)
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- Thiocarbonylthio compounds (S=C(Z)S-R) in free radical polymerization with reversible addition-fragmentation chain transfer (RAFT polymerization). Effect of the activating Group Z
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Free-radical polymerization in the presence of suitable addition-fragmentation chain transfer agents [S=C(Z)S-R] (RAFT agents) possess the characteristics of a living polymerization (i.e., polymer products can be reactivated for chain extension and/or block synthesis, molecular weights are predetermined by RAFT agent concentration and conversion, narrow polydispersities are possible). Styrene polymerizations (110°C, thermal initiation) were performed for two series of RAFT agents [S=C(Z)S-CH2Ph and S=C(Z)S-C(Me)2CN]. The chain transfer coefficients decrease in the series where Z is Ph > SCH2Ph ～ SMe ～ Me ～ N-pyrrolo ? OC6F5 > N-lactam > OC6H5 > O(alkyl) ? N(alkyl)2 (only the first five in this series provide narrow polydispersity polystyrene ( trithiocarbonates ～ dithioalkanoates > dithiocarbonates (xanthates) > dithiocarbamates. However, electron-withdrawing substituents on Z can enhance the activity of RAFT agents to modify the above order. Thus, substituents that render the oxygen or nitrogen lone pair less available for delocalization with the C=S can substantially enhance the effectiveness of xanthates or dithiocarbamates, respectively. The trend in relative effectiveness of the RAFT agents is rationalized in terms of interaction of Z with the C=S double bond to activate or deactivate that group toward free radical addition. Molecular orbital calculations and the estimated LUMO energies of the RAFT agents can be used in a qualitative manner to predict the effect of the Z substituent on the activity of RAFT agents.
- Chiefari, John,Mayadunne, Roshan T.A.,Moad, Catherine L.,Moad, Graeme,Rizzardo, Ezio,Postma, Almar,Skidmore, Melissa A.,Thang, San H.
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p. 2273 - 2283
(2007/10/03)
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- The Invention of Radical Reactions. Part XXI. Simple Methods for the Radical Deoxygenation of Primary Alcohols.
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Novel radical-chain deoxygenations of primary alcohols are described.The alcohols are acylated with the reagents pentafluorophenyl chlorothionoformate, 2,4,6-trichlorophenyl chlorothionoformate and 4-fluorophenyl chlorothionoformate and the intermediate thionocarbonates are deoxygenated with tributyltin hydride, triphenylsilane, diphenylsilane or phenylsilane in high-yielding reactions.Key Words: Thionocarbonates, Tributyltin hydride, Triphenylsilane, Diphenylsilane, Phenylsilane, Radical deoxygenations.
- Barton, Derek H. R.,Blundell, Paul,Dorchak, Joseph,Jang, Doo Ok,Jaszberenyi, Joseph Cs.
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p. 8969 - 8984
(2007/10/02)
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- IMPROVED METHODS FOR THE RADICAL DEOXYGENATION OF SECONDARY ALCOHOLS
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The reaction of Barton and McCombie has been improved by the use of the new reagents 2,4,6-trichlorophenoxythiocarbonyl chloride and its congener pentafluorophenoxythiocarbonyl chloride.Deoxygenations with these derivatives of 1,2:5,6-diacetoneglucofurano
- Barton, Derek H. R.,Jaszberenyi, Joseph Cs.
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p. 2619 - 2622
(2007/10/02)
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