Piperazine-2,5-diones chlorination

Covalent chlorinated impurities in MeSi(0Me)2 can be readily removed using Na and substantially reduce its rate of hydrolysis, while 3 amines accelerate the alcoholysis of Ph,SiCl, through silylated quaternary ammonium intermediates. The Bu (Ph)(MeO)Si group provides excellent protection to alcohols, its silyl acetal character providing for ready F cleavage, unlike Bu Ph2Si while analogues of the antibiotic bicyclomycin used bicyclic piperazine-diones as intermediates, and silylene protected dihydroxystyrene... 

Treatment of piperazine-2,5-diones, unsubstituted on the nitrogen atoms, with phosphorous oxychloride results in chlorination with simultaneous aromatization by loss of two hydrogen atoms [82JCS(P1)953] as shown in Scheme 16. 

Other chlorinations have been effected with phosphorus pentachloride alone as follows piperazine-2,5-dione in carbon tetrachloride to 2,5-dichloro-3,6-dihydropyrazine (847, 849) [but at 250°/24hours to tetrachloropyrazine (850, 851)] 2[Pg.102]

Degradation products from base treatment of cefaclor have not been isolated for characterization. A piperazine-2,5-dione (133) was obtained from refluxing the p-nitrobenzyl ester of cefaclor (132) in benzene. Cephalexin p-nitrobenzyl ester (130) in a parallel experiment had been shown to give 131. Quite unexpectedly, this degradation product of cefaclor contained no chlorine in elemental analysis the field desorption mass spectrum suggested the loss of HCl. The structure for 133 was derived from proton and C-NMR analyses. 

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