Free chemical reactions database
In the current form the question is addressed, and assuming you took a look at a listing of software already in the field like here, I speculate the sheer number of organic reactions (just some) alone renders such a task as a one-man / one-woman project too large.  There is a lot of work associated to create such a database, or software. Organic Synthesis is one open-access reference for organic reactions, yet the normal output is a html / pdf of the reaction procedure, and not a *.sdf (or other chemically relevant *.xml-like) format.  Inorganic Synthesis is a publication with similar intent as the former, yet not openly accessible.

Nevertheless, if you are interested in this topic, I suggest to consult the recent publications Computer-aided synthesis design: 40 years on (DOI 10.1002/wcms.61) as well as the just about a year old Computer-Assisted Synthetic Planning: The End of the Beginning in Angewandte Chemie (English version DOI: 10.1002/anie.201506101).