A map of the Sigma Draconis system
Sigma Draconis I was the first planet in the Sigma Draconis planetary system. This was one of six planets in this system that was not classified as M class; the others were Sigma Draconis II, Sigma Draconis V, Sigma Draconis VII, Sigma Draconis VIII, and Sigma Draconis IX. (TOS: "Spock's Brain")
Presumably, Sigma Draconis was located in the Alpha Quadrant.
According to the Star Trek: Star Charts (pgs. 19, 44), Sigma Draconis I was located in Sector 004 (Sigma Draconis sector).