DECLARE syntax-error in MySQL

I have this error that has to do with declare , and I tried many ways, but I can not fix it:

declare '@i' int
set @i = 1

while @i <=10 -- 1.000.000 filas    
begin    
  insert into neptuno.varchar_variable_dcha
  select top (100000)
    replace (cast(NEWID() as varchar(100)), '-','')
    + REPLICATE ('a',200-32)
  from pedidos
  cross join detalles_de_pedidos

  print cast (@i as varchar(100))

  set@i = @i + 1

end