Boosting voltage to power a solenoid (pulsing intermittantly)
This approach will work fine and is widely used for latching solenoids.  Remember that the voltage on the capacitor will start to drop when the solenoid is energized, and you must reach the solenoid rated current (not voltage) to get full force.  This means you must consider the inductance of the solenoid coil.  The catch diode must be capable of handling the full solenoid current.  Make sure the diode is in close proximity to the coil.