Ex4 does work, and I don't see the difference between the alphas.
(* Title: Quotient_Syntax.thy
Author: Cezary Kaliszyk and Christian Urban
*)
header {* Pretty syntax for Quotient operations *}
(*<*)
theory Quotient_Syntax
imports Quotient
begin
notation
rel_conj (infixr "OOO" 75) and
fun_map (infixr "--->" 55) and
fun_rel (infixr "===>" 55)
end
(*>*)