Opening 1NT with Two Doubletons?
It depends on a lot of things. No clear answer.
1) Quality of the doubletons -- if xx and xx, quite unlikely I'd open 1NT. If KQ and KJ doubleton, much more likely to open 1NT.
2) What is the 5-card suit? If a major, usually I wouldn't open 1NT (but see #4). I would open in the major since I have no rebid problem (can rebid in the 4-card suit next).
3) What is the 4-card suit?