A New Chemical Desulfurization Method

First Enantioselective Total Synthesis of Both (+)- and (−)-Metachromin A

“…The use of Raney nickel (W2,17 freshly prepared), even after its deactivation in boiling acetone,18 led to reduction and isomerization of the double bonds but not to complete desulfuration. Treatment with hydrazine19 resulted in complete decomposition of the compound. Birch conditions,20 at the temperature of boiling ammonia as well as at −50 °C, led to reduction of the electron‐rich benzene ring, while at −78 °C a mixture of compounds with only one reductively cleaved C−S bond was detected.…”

Synthesis of 6-Styrylheptalenes

“…Although 18 and 19 can be recognized on TLC, any attempt to separate the mixture either by column chromatography on silica gel or by preparative TLC failed. Since all other reduction methods either under basic [14] or acidic conditions [15] affected the thioacetal group, we were not able to obtain 18 without formation of 19. Finally, 18 was found to crystallize much easier than 19 from hexane, and the fractional crystallization afforded pure 18 in 52% yield.…”

Desulfurization of Thioketals into Methylene and Methyl Derivatives: Nickel or not Nickel?

“…Giorgian and co‐workers reported first in 1959 that hydrated hydrazine was able to desulfurize cyclic or acyclic thioketals in the presence of KOH . They also showed that KOH was useful but not essential in this reducing process but lowered considerably the effective temperature of reactions.…”

“…Five years after the pioneer work of Giorgian, Corey described the total synthesis of Longifolene and studied the desulfurization of the dithiolane described in Scheme . The authors reported that Raney‐Ni was ineffective in achieving this transformation, on the contrary to hydrazine associated with Na, which quantitatively desulfurized the dithiolane into the expected methylene compound.…”