Hydrosulfite reduction of N ‐nitroso‐1,2,3,4‐etrahydroisoquinolines and oxidation of N ‐amino‐l,2,3,4 tetrahydroisoquinolines

The sodium hydrosulfite reduction of N ‐nitroso‐1,2,3,4‐tetrahydroisoquinoline ( 5 ) does not result in the loss of nitrogen and leads to the corresponding hydrazine 6 which upon oxidation with mercuric oxide in ethanol at 62° gives the hexahydrotetrazine 7 in 39% yield. Treatment of the N ‐tosyl derivative of 6 with base affords 7 in nearly quanitative yield. Oxidation of 6 in 1‐butanol at 95° results in the formation of a complex product mixture from which only one component, 1,1′‐azobis‐3,4‐dihydroisoquinoline ( 8 ) could be isolated. Surprisingly the sodium hydrosulfite reduction of 2‐nitroso‐3‐phenyl‐1,2,3,4‐tetrahydroisoquinoline ( 15 ) also failed to proceed with loss of nitrogen and yields the corresponding hydrazine 16 . However, 16 was cleanly oxidized by mercuric oxide in ethanol at 62° with concurrent elimination of nitrogen to afford 2‐phenylindane in 75% yield. Possible rationalizations for these results are presented.