Information extraction with reinforcement learning, feasible?
You ideally want to use Reinforcement Learning in situations where there is delayed feedback and stochastic transitions in the environment. Although you could potentially apply RL, in your case, you might be better off with a Sequence to Sequence learning framework (https://papers.nips.cc/paper/5346-sequence-to-sequence-learning-with-neural-networks.pdf) since you have access to the entire sentence and there is no stochasticity involved. 

On the topic of RL with Information Extraction, this might be of interest:
Improving Information Extraction by Acquiring External Evidence with Reinforcement Learning (http://arxiv.org/abs/1603.07954)