Decarbonylation of Acid Chlorides and Aldehydes

At elevated temperature, RhCl(PPh3)3 becomes a catalyst (or catalyst precursor) for the decarbonylation reaction. Acid chlorides are reported to be decarbonylated catalytically at A recent report has 

The essential question to be addressed is whether the rhodium complex re-enters the decarbonylation sequence previously discussed (Equation 7) or if a different pathway is available at elevated temperature. Loss of CO from RhCl(CO)(PPh3)2 is not observed even at high temperature (300 C) or under UV irradiation.Therefore, mechanisms that have been proposed involve either oxidative addition to this complex or loss of CO from the alkyl-rhodium carbonyl complex. These two mechanisms 

Catalyst PPh3 (eq.) PPh3/Rh Time (h) PhCH2Cr Catalytic activity (turnovers/hr) 

It seems reasonable that some alternate pathway may exist for the following reasons  

A plausible, but speculative, reaction scheme for the catalytic decarbonylation of acid chlorides (and aldehydes) that involves phosphine dissociation from one of the Intermediates has been postulated. It is clear, though, that there are presently not enough facts to substantiate this hypothesis. Future work on the mechanism of catalytic decarbonylation using RhCl(CO)(PPh3)2 and other catalysts which investigates phosphine inhibition could be very informative. 

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