This preview shows page 1. Sign up to view the full content.
Unformatted text preview: (recall-benzene and H 2 O form an azeotrope). • Ketals and acetals, which are stable to non-acidic conditions, can be used as protecting groups for ketones and aldehydes. • The mechanism for ketal/acetal hydrolysis is the reverse of the mechanism for ketal/acetal formation. Aqueous acid will promote the “hydrolysis” a ketal/acetal. • The mechanism for formation of thio-acetals (i.e. 1,3-dithianes) is analogous to ketal formation.1,3-dithianes can be deprotonated by n-BuLi. The resulting carbanion is a good nucleophile. Once the dithiane is alkylated, it may be hydrolyzed using HgCl 2 , H 2 O-CH 3 CN to produce a ketone. Thus, using dithiane chemistry, we can convert aldehydes to ketones. • Thus far, we’ve examined the addition of O- and S-nucleophiles to aldehydes and ketones. Next, we discuss additions involving C-nucleophiles....
View Full Document
This note was uploaded on 03/31/2009 for the course CH 318M taught by Professor Bocknack during the Spring '08 term at University of Texas at Austin.
- Spring '08