This is a bit convoluted, but...
A helpless character is paralyzed, held, bound, sleeping, unconscious, or otherwise completely at an opponent’s mercy. A helpless target is treated as having a Dexterity of 0 (-5 modifier). Melee attacks against a helpless target get a +4 bonus (equivalent to attacking a prone target). Ranged attacks gets no special bonus against helpless targets. Rogues can sneak attack helpless targets. From the Helpless section.
A character with Dexterity 0 is paralyzed. From ability damage section.
So, if you are helpless, you are by default treated as paralyzed.
A paralyzed character is frozen in place and unable to move or act. A paralyzed character has effective Dexterity and Strength scores of 0 and is helpless, but can take purely mental actions. A winged creature flying in the air at the time that it becomes paralyzed cannot flap its wings and falls. A paralyzed swimmer can’t swim and may drown. A creature can move through a space occupied by a paralyzed creature—ally or not. Each square occupied by a paralyzed creature, however, counts as 2 squares.
So, you can make only mental actions while you are sleeping. If you can make a case that making a reflex save is purely mental action, then I guess you get a reflex save while sleeping.
A helpless character is paralyzed, [...] sleeping, unconscious.
A is B, B2, and B3.
A helpless target is treated as having a Dexterity of 0 (-5 modifier).
A is C.
A character with Dexterity 0 is paralyzed. C
Fixed that, you had it backwards.
Also, if A = B and A = C, then C = B anyway.
If A = B, A = C, and B = C, then all terms above grant all condition
A paralyzed character has effective Dexterity and Strength scores of 0 and is helpless.
C is B and A.
A paralyzed character [...] can take purely mental actions.
C can D.
B is not necessarily A. B2 isn't necessarily A, B, B3, nor C. In the preceding sentence, B2 interchanged with B3, is. Ergo, an opponent being paralyzed
is not premise "to deliver a coup de grace
". I don't want to mess with this anymore; I don't want to have to read all of this
, right now.