Enamine chemistry—XXII: The preparation of 4-acylaminopent-3-en-2-ones and the corresponding enamino-thiones

Acylation of 4-aminopcnl-3-en-2-one, 5, with different acid chlorides, RCOCl(R = Me, Me₂CH, Me₃C, C₆H₅, CICH₂) gives only N-acylated products, 6, in high yields. The N-acylated enaminones, 5, are shown only to exist m the Z-s-Z form in solution. The UV spectra of 6 are discussed and an additional increment to the Dabrowski-Table²¹ is given. The reaction of 6 with 2,4-bis(4-methoxyphenyl)-1,2,3,4-dithiadiphosphetane 2,4-disulfide, 2, at room temperature in DME gives the corresponding enamino-thiones, 7, in good yields. The ¹H and ¹³C NMR spectra of 6 and 7 are discussed.