Context : 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 \pm 0.10 dex ) .

Aims : 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 .

Methods : 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 .
Iron abundances from { Fe \textsc { i } } and { Fe \textsc { ii } } lines have also been measured and used to check the atmospheric model parameters .

Results : The Li line is detected in 27 stars confirmed as likely cluster members by repeated radial velocity measurements .
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 { ( Li ) } = 2.70 dex , which is substantially higher than that observed in 47 Tuc .
We estimated an iron abundance of [ Fe/H ] = -0.54 \pm 0.10 dex for NGC 2243 , which is similar ( within the errors ) to previous findings .
The [ \alpha /Fe ] content ranges from 0.00 \pm 0.14 for Ca to 0.20 \pm 0.22 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 km s ^ { -1 } for the cluster .

Conclusions : We confirm a correlation between the Li dip cool-side position in mass as a function of the cluster ’ s [ Fe/H ] .
The Li abundance found in the metal-poor OC NGC2243 agrees well with results obtained for the interstellar medium in the Small Magellanic Cloud ( SMC ) having similar low metallicity .
This value of Li is comparable to the primordial Li abundance deduced from WMAP measurements , therefore putting strong constraints on the models of Li enrichment during the early history of our Galaxy .