10.1002/chem.201703875
Chemistry - A European Journal
COMMUNICATION
enhanced reactivity of DPDS and compatibility with telescoped
reactions.
equiv). The reaction was sealed with a PTFE septum in a screw
cap and stirred at 23 °C. After 48 h, the reaction was diluted to 3
mL with ethyl acetate and 1.5 mL of 2.0 N NaOH was added to
quench the reaction (warning: gas evolution) and stirred for 15
min. The layers were separated and the organic layer was
concentrated directly onto silica gel. The mixture was purified by
column chromatography with hexanes to afford phosphine 2a
(65 mg, 0.25 mmol, 99%) as a white solid.
Acknowledgements
.
This work was supported by startup funds from the University of
Minnesota to CCA. JAB thanks the National Science Foundation
(pre-doctoral fellowship, GRFP-ID: 00039202), the University of
Minnesota College of Pharmacy (Bighley fellowship), and the
University of Minnesota Graduate College (doctoral dissertaion
fellowship) for financial support. CGE thanks the National
Institutes of Health Chemistry-Biology Interface training grant
(T32-GM008700) for financial support.
Scheme 2. The domino synthesis of trivalent phosphines from
secondary phosphine oxide 1p.
In conclusion, we utilized the disiloxane DPDS as
a
chemoselective reducing agent of acyclic phosphine oxides.
This reagent could be deployed alone at 110 °C to afford high
yields of phosphines very rapidly or used in tandem with the
Brønsted acid BNPA in reductions at ambient temperature. This
represents the first broadly applicable additive-free reduction of
phosphine oxides as well as the first demonstration of room
temperature silane-mediated reduction of acyclic phosphine
oxides. Both sets of conditions display exquisite functional group
tolerance and are simple to set up, as the reactions do not
require the removal of air or water. We expect these
methodologies to improve existing syntheses, facilitate the
construction of new phosphines, and provide a route towards
improving catalysis in redox recycling reactions.[15,16] We are
currently exploring the mechanism of DPDS reductions and
applications of this reagent in redox catalysis.
Keywords: Phosphine oxides • Silane reductions •
Chemoselective methods• Disiloxane • Synthetic methods
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Experimental Section
Typical procedure for additive-free reductions of phosphine
oxides: To a 2-dram vial equipped with a ¼” teflon-coated stir
bar was added phosphine oxide 1a (139 mg, 0.5 mmol, 1.0
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