5252F is wired as such
BAT: TO-94[Pin2] / DIP-8[Pin7] = Inductor + (Optional on/off switch) + Bat Positive
VSS: TO-94[Pin3] / DIP-8[Pin2] = Led Cathode + Bat Negative
LX: TO-94[Pin4] / DIP-8[Pin3] = Inductor + Led Anode
gchart made a joule thief that that runs down to 0.7v with TLV61220 or ZXLD381