lecture 7

• Acidity of 1,3-Dithianes

  -anion formed is relatively stable

  -donation of electrons into the empty 3d orbital of sulfur

  -donation into empty pi* orbital on C-S bond
• Mechanism of hydrolysis

  -Dithianes more stable than acetals, cant use H+ as a catalyst

  -HgCL2 used to facilitate hydrolysis

  -Hg(III) acts as a lewis acid, forms strong coordination complex with sulfur
• Umpolung reagents


  -natural polarity of carbonyl carbons is delta positive, electrophilic

  -In anion from 1,3 dithianes the polarity is reversed and the carbon is nucleophilic
• Reduction of 1,3 Dithianes to methylenes

  -through hydrogenation with a Raney nickel catalyst