The known 1,1-bis(trimethylsilyloxy)ketene acetal 1a was prepared by deprotonation of phenylacetic acid with lithio-1,1,1,3,3,3-hexamethyldisilazane and subsequent addition of trimethylchlorosilane to the dianion thus formed. [15] The reaction of 1a with oxalyl chloride (2) in the presence of trimethylsilyl-trifluoromethanesulfonate (Me 3 SiOTf) afforded the 3-hydroxymaleic anhydride 3a in up to 70% yield (Scheme [1] ). [16] The direct reaction of the dianion of phenylacetic ...
