The Deoxygenation of Phosphine Oxides under Green Chemical Conditions

Abstract

The deoxygenation of a few diaryl‐phenylphosphine oxides, dimethyl‐phenylphosphine oxide, and 3‐methyl‐1‐phenyl‐3‐phospholene 1‐oxide was studied by phenylsilane, tetramethyldisiloxane (TMDS), and polymethylhydrosiloxane (PMHS) under conventional or microwave (MW) heating, in toluene or in the absence of any solvent at different temperatures. It was found that the deoxygenation with TMDS or PMHS under MW and solvent‐free conditions may be the method of choice and provides a green chemical approach.

Metal-Free Reduction of Phosphine Oxides Using Polymethylhydrosiloxane

“…In the case of 1, increasing the amount of PMHS from 5 to 15 equiv. at 250 • C increased the conversion after 1 h significantly, from 45% to 90% (Entries 2 and 4), which under related conditions was also found by Fritzsche, et al [8][9][10] and Keglevich, et al [11].…”

“…We present here results on the reduction of a small library of industrially-relevant phosphine oxides using PHMS in modest stoichiometric excess, with good results for activity and selectivity, where we first benchmark our experimental set-up with the results of Keglevich, et al [11] by studying the triphenylphosphine oxide reduction under related conditions, then study the kinetics of this deoxygenation reaction, and subsequently extend the scope to trialkylphosphine oxides. Examples of water-soluble phosphine oxides reduction with PHMS, a case often neglected in the literature, are also shown for the first time.…”

“…A study by Keglevich, et al. demonstrated the efficient use of PMHS for the reduction of a number of triphenylphosphine oxide derivatives, with reaction times ranging from 7 to 16 h [11]. An improved protocol was obtained using trichlorosilane (1 equiv.…”

A study on the deoxygenation of trialkyl‐, dialkyl‐phenyl‐ and alkyl‐diphenyl phosphine oxides by hydrosilanes

“…During our earlier work, we studied the deoxygenation of 1‐phenyl‐3‐methyl‐3‐phospholene 1‐oxide ( 1 ) by different silanes ( 3 ‐ 10 ) in detail . The most important results are summarized in Scheme 1 and Table .…”

“…The most important results are summarized in Scheme 1 and Table . The expensive phenylsilane (PhSiH 3 ) 3 was found to be the best reagent under solvent‐free and microwave (MW)‐assisted conditions that could be replaced well by TMDS ( 4 ) and PMHS ( 5 ), although somewhat higher temperatures and longer reaction times were necessary (Table , entries 2 and 3 vs 1) . Later on, other silanes were also tried out .…”