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.