  Lithium is a fundamental element for studying the mixing mechanisms acting in
the stellar interiors, for understanding the chemical evolution of the Galaxy
and the Big Bang nucleosynthesis. The study of Li in stars of open clusters
(hereafter OC) allows a detailed comparison with stellar evolutionary models
and permits us to trace its galactic evolution. The OC NGC 2243 is particularly
interesting because of its low metallicity ([Fe/H]=$-0.54 \pm0.10$ dex). We
measure the iron and lithium abundance in stars of the metal-poor OC NGC 2243.
The first aim is to determine whether the Li dip extends to such low
metallicities, the second is to compare the results of our Li analysis in this
OC with those present in 47 Tuc, a globular cluster of similar metallicity. We
performed a detailed analysis of high-resolution spectra obtained with the
multi-object facility FLAMES at the ESO VLT 8.2m telescope. Lithium abundance
was derived through line equivalent widths and the OSMARCS atmosphere models.
We determine a Li dip center of 1.06 $M_\odot$, which is much smaller than that
observed in solar metallicity and metal-rich clusters. This finding confirms
and strengthens the conclusion that the mass of the stars in the Li dip
strongly depends on stellar metallicity. The mean Li abundance of the cluster
is $\log n{\rm (Li)}=2.70$ dex, which is substantially higher than that
observed in 47 Tuc. We estimated an iron abundance of [Fe/H]=$-0.54 \pm0.10$
dex for NGC 2243, which is similar (within the errors) to previous findings.
The [$ \alpha$/Fe] content ranges from $0.00\pm0.14$ for Ca to $0.20\pm0.22$
for Ti, which is low when compared to thick disk stars and to Pop II stars, but
compatible with thin disk objects. We found a mean radial velocity of 61.9
$\pm$ 0.8 \kms for the cluster.
