ORGANIC
LETTERS
2009
Vol. 11, No. 15
3190-3193
Phase-Vanishing Reactions with PTFE
(Teflon) as a Phase Screen
Nathan J. Van Zee and Veljko Dragojlovic*
Wilkes Honors College of Florida Atlantic UniVersity, 5353 Parkside DriVe,
Jupiter, Florida 33458
Received May 7, 2009
ABSTRACT
Phase-vanishing reactions are triphasic reactions, which involve a reagent, a liquid perfluoroalkane, and a substrate. In a phase-vanishing
reaction with PTFE tape as the phase screen instead of a liquid perfluoroalkane, there is no limitation related to the density of a phase and
the denser phase can be in the top layer. The reactions were faster compared to traditional PV reactions, and it was possible to carry out
sequential and tandem reactions and reactions under a reflux.
Phase-vanishing (PV) reactions are triphasic reactions, which
involve a reagent, a liquid perfluoroalkane, and a sub-
strate.1-11 The perfluoroalkane, which is in the layer between
the two, acts as a phase screen. It is inert and is used to
separate the reactants. As the reagent diffuses through the
perfluoroalkane layer, it reaches the substrate layer and reacts
with it. Thus, the reaction proceeds at a moderate rate, instead
of a vigorous and often violent reaction if the two reactants
were mixed without a solvent. In the course of the reaction,
the reagent disappears (“vanishes”).
warming potential (GWP ∼10,000) and atmospheric lifetime
of 3200 years.14 Although in a PV reaction FC-72 is used
in a closed system and can be either reused or recovered for
future use, it also has a low boiling point, and one has to be
careful to minimize losses. In addition, some solvents,
reagents, and reaction products are partially soluble in FC-
72,5,12,13,15 which limits our ability to either reuse or
completely recycle it.
Ryu and Curran have reported advantages in using heavier
liquid perfluoro compounds as phase screens.16 Herein we
report use of a solid perfluoro compound, PTFE (Teflon
tape), as a phase screen.
In a phase-vanishing PTFE (PV-PTFE) reaction setup, the
substrate in a solvent was placed in a reaction vessel, such
as a vial, test tube, or flask. The reagent was placed in a
delivery vessel, such as a glass tube, and sealed on both ends
with PTFE tape. This tube is then inserted into the reaction
vessel so that both reactants are in contact with the PTFE
PV conditions allow for reactions that otherwise would
be too vigorous without a solvent to be performed on neat
reagents.12,13 This considerably simplifies the work-up.
However, fluorinert liquid FC-72 (C6F14) has a high global
(1) Ryu, I.; Matsubara, H.; Yasuda, S.; Nakamura, H.; Curran, D. P.
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(13) Windmon, N.; Dragojlovic, V. Tetrahedron Lett. 2008, 49, 6543–
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(14) 3M Fluorinert Electronic Liquid FC-72 Product Information. http://
multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTtnxTE5XF-
6EVuQEcuZgVs6EVs6E666666--. Accessed on March 23, 2009.
(15) Chu, Q.; Yu, M. S.; Curran, D. P. Tetrahedron 2007, 63, 9890–
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(16) Ryu, I.; Matsubara, H.; Nakamura, H.; Curran, D. P. Chem. Rec.
2008, 8, 351–363.
.
10.1021/ol901450h CCC: $40.75
Published on Web 07/08/2009
2009 American Chemical Society