A Study on the Deoxygenation of Phosphine Oxides by Different Silane Derivatives

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 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 . It was found that 1‐naphthylsilane (NaphSiH 3 6 ), benzylsilane (BnSiH 3 7 ), and bis(4‐methylphenyl)silane [(4‐MePh) 2 SiH 2 8 ] were more reactive than PMHS ( 5 ) and TMDS ( 4 ) (Table , entries 4–6), but tetraphenyl‐disilane ([Ph 2 SiH] 2 10 ) and bis(1‐naphthyl)silane ([1‐Naph] 2 SiH 2 9 ) were less reactive than PMHS ( 5 ) (Table , entries 7 and 8).…”

“…Deoxygenation of 3‐methyl‐1‐phenyl‐3‐phospholene 1‐oxide ( 1 ) by silanes under solvent‐free, microwave‐assisted conditions…”

“…We experienced that in heterogeneous phase C‐alkylations, and in Kabachnik‐Fields reactions, the catalysts could be omitted under MW conditions. It was shown above that this approach was utilized in the TMDS‐ and PMHS‐promoted deoxygenations . Due to their lower reactivity, TMDS and PMHS were advised to be applied together with metal‐containing or metal‐free catalysts .…”

“…Due to their lower reactivity, TMDS and PMHS were advised to be applied together with metal‐containing or metal‐free catalysts . We found that under MW irradiation, there is no need for any catalyst (Table , entries 2 and 3) …”