[volksmacke]

What's the mechanism of this reaction? I suspect it is a stepwise cycloaddition of the dichloroethylene to the benzyne (resulting from the thermal decomposition of the carboxybenzenediazo salt), but how did the ketone functionality get there? It seems that the propylene oxide is the source of oxygen, but how?

Source: https://doi.org/10.1021/jo01294a012

[clarkstill]

Have you misread the paper perhaps? From the experimental section, this cocktail of reagents forms 1,1-Dichlorobenzocyclobutene (presumably by formal 2+2 cycloaddition between the benzyne and dichloroethene). They then treat this compound with H2SO4 to convert the dichloromethylene group into a ketone so the compound becomes Benzocyclobutenone. It isnt clear to me what the role of the propylene oxide is, perhaps to mop up the HCl formed in the benzyne formation?

[volksmacke]

Indeed i have.... Thank you.