Chemo- and Product-selective Electrooxidation of 3-(Arylthiomethyl)-Δ³-cephems

Abstract

Electrolysis of 3-arylthiomethyl-D 3 -cephems possessing various substituents on the arylthio moiety undergo chemoselective and product-selective electrooxidation to give several different products. These include isomeric mixtures of the corresponding methoxylated cephems, a bis[(D 3 -cephem-3-yl)methyl]disulfide or a 3-dimethoxymethyl-D 3 -cephem. The selectivity of the oxidation is highly dependent on the nature of the substituents on the arylthio moiety which suggests that both steric and electronic effects play an important role in the electrooxidation of 3-arylthiomethyl-D 3 -cephems.

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“…For example, electro-oxidation of 3-(arylthiomethyl)-Δ 3 -cephem was utilized to synthesize a 3-methoxy-cephem analog when attempted displacement of the analogous allyl chloride did not yield the product in satisfactory yields (Figure 14F). 242 Barba and co-workers reported an efficient method to convert xanthates into thiocarbonates through anodic oxidation. 243 …”

“…For example, electro-oxidation of 3-(arylthiomethyl)-Δ 3 -cephem was utilized to synthesize a 3-methoxy-cephem analog when attempted displacement of the analogous allyl chloride did not yield the product in satisfactory yields (Figure 14F). 242 Barba and co-workers reported an efficient method to convert xanthates into thiocarbonates through anodic oxidation. 243 Fry has demonstrated that electrochemical oxidation using a silane auxiliary can lead to an unstabilized α-carbonyl cation which readily rearranges to the lower energy benzyl cation (Figure 14G).…”

“…Aside from oxocarbenium and thionium cations, sulfur- or silicon-based electroauxiliaries also offer a convenient means to access other stabilized carbocations such as allylic cations. For example, electro-oxidation of 3-(arylthiomethyl)-Δ 3 -cephem was utilized to synthesize a 3-methoxy-cephem analog when attempted displacement of the analogous allyl chloride did not yield the product in satisfactory yields (Figure F) . Barba and co-workers reported an efficient method to convert xanthates into thiocarbonates through anodic oxidation …”