University:
York University
Course:
CHEM 2021 | Introductory Organic Chemistry II
Academic year:

2023
Views:

356

Pages:

2
Author:

Niklas

Synthesis of Dithianes: Problem: The given starting material (a ketone) is very reactive with Grignard reagents (GR). Solution: Use protecting groups like ketals, acetals, or dithianes to protect the carbonyl group. Dithiane Protection: Formation of Dithiane: React the ketone with 1,3-propanedithiol and acid catalyst (H+) to form the corresponding dithiane. Grignard Reaction: The dithiane can undergo a Grignard reaction with an alkyl halide to introduce a new carbon chain. Deprotection: Treat the product with mercury (II) chloride (HgCl₂) and water (H₂O) to remove the dithiane protecting group, regenerating the ketone with the desired alkyl group. Dithianes: 1. Formation of Dithiane: A ketone reacts with 1,3-propanedithiol in the presence of an acid catalyst (H+) to form a dithiane. 2. Grignard Reaction: The dithiane can undergo a Grignard reaction with an alkyl halide (MgBr) to introduce a new carbon chain. Protonation (H+) is required to remove the Grignard reagent. 3. Deprotection: Treatment with mercury(II) chloride (HgCl₂) and water (H₂O) removes the dithiane protecting group, regenerating the ketone with the desired alkyl group. Alternatively, Raney Nickel (Raney Ni) with H₂ in ethanol (EtOH) can also be used for deprotection. Know Outcome: The desired product is a ketone with a new alkyl group introduced