A study showing the influence of different percentages of moisture content (% w/w) in THF, determined by Karl Fischer (KF) titration, was conducted. For the sake of comparison, all experiments were performed at the same scale using properly dried reagents obtained from the same batch, with the goal of minimizing any adverse result caused by different reagents' quality. As expected, the increase of water content in the solvent worsened the conversion of the starting materials toward the product. Solvent containing 0.05 to 0.1 % w/w of water provided similar results and good conversion of starting materials based on the HPLC A % analysis; d.r. for both cases was ~4:1, and the syn-diastereomer pair, 3 and ent-3, area was ~60 % (Graph 4). When the water content was 0.2 % w/w, the conversion of 1 and 2 decreased, and d.r. was reduced to 1.4:1. In addition to the partial quench of the lithiated species 1a and of the lithium amide base 11, the presence of water in the system is likely to have a role in perturbing the formation of the lithium aggregates, which ultimately results in the noticeable d.r. variations. Solvent water content > 0.5 % w/w shut down the desired reaction, and only 2 % of the syn-diastereomer pair was detected. Quinoline 1 corresponded to the major component in the mixture (53 %) and the 1,4-addition side product 20 was formed to a larger extent (17 %) since the neutral form of amine 11 can catalyze the formation of enone 19 through ketone 2 enolization, and then act as a nucleophile in the 1,4-addition.