Alkylation of the enaminothiones 1 and 5 in the presence of base leads
to the products 2 and 6 with preponderant or exclusive Z- configurati
on about the C=C. Acid catalysed equilibration of 2 leads to a mixture
in which the E- isomer predominates, whereas in the case of 6, the Z-
form appears to be the thermodynamically favoured one.