Thiadiazoles as Substrates

Like their selena analogues (Section 2.1.15), these thiadiazoles have been neglected as substrates for pyrazines. However, 4-p-anisidino-2-(3-ethoxycarbony-lacetonyl)-2,3-dihydro-l,2,5-thiadiazol-3-one 1-oxide (80) afforded 3-p-anisidino-5-cthoxycarbonyhnethyl-2( I // )-pyra/iiione (81) in 30% yield by standing with N,. V-diet hyI - (V- i sopropy I a m i n e at 20°C for 3 days.289 

5-cthoxycarb()nylmethyl-2fl//)-pyrazinone (81) in 30% yield by standing with N, 7V-diethyl- /-isopropylamine at 20°C for 3 days.  

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