Thiocyanates molecular geometry

The synthesis of pyranoid sugar derivatives having an episulfide group fused to the ring involves requirements of molecular geometry more critical than for episulfides on an acyclic chain. Conversion of an epoxide in a locked-ring system to an episulfide by the action of thiourea or thiocyanate ion is diflicult, because reactions of this type involve a trans-fused, cyclic intermediate (91), formation of which requires a [Pg.179]

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