Efficient synthesis of 5,6-dihydro-8H-[1,2,4]thiadiazino[6,5,4-de] phenanthridine 4,4-dioxide and 5,6-dihydro-8H-[1,2,4]-thiadiazino[6,5,4-ij] thieno[2,3-c]quinoline 4,4-dioxide