Well that won't work. In this case I would use two variables based off of the same value such as :

DECLARE @mydate datetime, @mydatestring varchar(20)

SELECT @mydate = getdate()

SELECT @mydatestring = CONVERT(CHAR(9),@mydate,1) + SUBSTRING(CONVERT(CHAR(5),@mydate,14),1,5) + ' '

PRINT @mydatestring

INSERT INTO TableA (columnA)

SELECT @mydate