Hi,
Not sure, just read circuit has several limitations, one being 555 current limit of 200mA; another being timer Vout is always 1 - 2V below V+ (3.7V * 2) - ~2V... - and the load influences that; also, charge diode-capacitor pumps are weak current-wise. I breadboarded a voltage inverter and a doubler with a timer and diode-caps months ago out of curiosity and I doubt I would use either in a real application, especially one that required more than a few mA, but each to their own preferences. Give it a go in a simulator or breadboard it and find out if it's suitable for the circuit needs. Have you seen the version using a complementary pair on the timer output? There's also a version that parallels two timers outputs to "double" the voltage.