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

The sodium hydrosulfite reduction ofN‐nitroso‐1,2,3,4‐tetrahydroisoquinoline (5) does not result in the loss of nitrogen and leads to the corresponding hydrazine6which upon oxidation with mercuric oxide in ethanol at 62° gives the hexahydrotetrazine7in 39% yield. Treatment of theN‐tosyl derivative of6with base affords7in nearly quanitative yield. Oxidation of6in 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 hydrazine16. However,16was 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.