Abstract
The recently reported chemoselective reduction of phosphine oxides with 1,3-diphenyldisiloxane
(DPDS) has opened up the possibility of additive-free phosphine oxide reductions in
catalytic systems. Herein we disclose the use of this new reducing agent as an enabler
of phosphorus redox recycling in Wittig, Staudinger, and alcohol substitution reactions.
DPDS was successfully utilized in ambient-temperature additive-free redox recycling
variants of the Wittig olefination, Appel halogenation, and Staudinger reduction.
Triphenylphosphine-promoted catalytic recycling reactions were also facilitated by
DPDS. Additive-free triphenylphosphine-promoted catalytic Staudinger reductions could
even be performed at ambient temperature due to the rapid nature of phosphinimine
reduction, for which we characterized kinetic and thermodynamic parameters. These
results demonstrate the utility of DPDS as an excellent reducing agent for the development
of phosphorus redox recycling reactions.
Key words
organocatalysis - disiloxanes - olefination - azide reduction - halogenation - phosphines
