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p-Methoxybenzyl, diphenylmethyl, and tert-butyl esters were deprotected by gentle heating in phenol. This method of ester cleavage played an important role in p-ladam synthesis. The mechanism of the reaction is believed to involve a proton relay through a hydrogen-bonded phenolic matrix.(7) A precedent exista in the case of the hydrolysis of N-(benzyloxycarbonyl)-L-proline benzhydryl ester by TFA and phenol. However, a relatively large amount of TFA (1 mL) and phenol (0.2 g) were used to cleave 0.41 g (1 mmol) of the ester. See: Stelekatoa, G. C.; Paganou, A.; Zervas, L.

Enols may be synthesized independently of their more stable, keto tautomers; enols are not inherently unstable.

A novel access to 3-hydroxycephems was attained from penicillin G via the C=C bond cleavage of 1-(1-alkoxycarbonyl-2-chloromethyl-2-propenyl)-4-(phenylsulfonylthio)-2-azetidinones by successive treatment with RuCl3/HIO4 and HIO4/CuSO4 and reductive cyclization of 1-(1-alkoxycarbonyl-3-chloro-2-hydroxy-1-propenyl)-4-(phenylsulfonylthio)-2-azetidinones on treatment with a newly devised BiCl3/Sn or TiCl4/Sn bimetal redox couple in DMF containing pyridine.

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