Azetes as Substrates

Treatment of the /3-lactam, 3,3-dimethoxy-l-p-methoxyphenyl-4-p-methoxyphenyliminomethyl-2-azetidinone (3, R = H), with stannous chloride in dichloromethane for 20 h gave 1,4-bisf/ -methoxyphenyl)-2,3(l//,4//)-pyrazine-dione (5, R = H) in 95% yield by ring expansion via the acetal (4) 874 the 4-methy-lated substrate (3, R = Me) likewise gave 1,4-bisf p-methoxyphenyl)-5,6-dimcthyl-2,3(lH,4tf)-pyrazinedione (5, R = Me) (99%).874 cf-1740 

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