Author Topic: Methyleneation of Ketones?  (Read 3092 times)

0 Members and 1 Guest are viewing this topic.

Vibrating_Lights

  • Guest
Methyleneation of Ketones?
« on: June 18, 2003, 07:33:00 AM »
In this synth

https://www.thevespiary.org/rhodium/Rhodium/chemistry/methylenation.html


-------
11.0 grams (0.1 mol) catechol is dissolved in 1000ml of 20% NaOH, and 3.2 grams (0.1 mol) of cetyltrimethylammonium bromide is added. The mixture is heated to 60°C for 30 minutes and then allowed to cool to room temperature, whereupon 21.2 grams (0.25 mol) of dichloromethane is added with stirring. The mixture is then heated to 80°C with a good reflux condenser for 5 hours, the solution saturated with NaCl and filtered. The solution is then extracted with 3x50 ml CH2Cl2, the pooled extracts washed with 50ml 20% NaOH to remove any phenolic materials, and then with 50 ml brine. The solution is dried over MgSO4, and the solvent removed under vacuum. Yield 90% of 1,3-benzodioxole.
------
Could the Phenylacetone be methyleneated in this this manner without anything reacting with the carbonyl group.


Aurelius

  • Guest
Yields
« Reply #1 on: June 18, 2003, 12:29:00 PM »
Yields would probably suffer a little bit, but you could probably do it.


Lilienthal

  • Guest
Ketones in the presence of base would ...
« Reply #2 on: June 19, 2003, 12:41:00 AM »
Ketones in the presence of base would polymerize due to an aldol condensation. Protecting the ketone as an acetal might help.

Aurelius

  • Guest
Try the reaction
« Reply #3 on: June 19, 2003, 11:37:00 AM »
on a small scale with and without protection to see which gives better overall yields.  If the NaOH is only 20% then I don't think that condensation will predominate.  It will happen, but is it to such a degree as to warrant the use of a protecting agent (adding and removing slightly lowers yields- unless we have a patent that shows quantitative addition and removal).


Vibrating_Lights

  • Guest
Phlactamide
« Reply #4 on: June 19, 2003, 02:14:00 PM »
would the phlactamide be suitable to make the rxn work??
VL_


Aurelius

  • Guest
Amide as a protecting group?
« Reply #5 on: June 19, 2003, 06:45:00 PM »
With low temperatures and quick reaction times you should be ok, but I think the amide might hydrolyze (basic conditions)