March 29, 2024, 10:08:17 AM
Forum Rules: Read This Before Posting


Topic: Reaction of A,B steroid ring lactone with grignard reagent  (Read 4571 times)

0 Members and 1 Guest are viewing this topic.

Offline TheAlbatross58

  • New Member
  • **
  • Posts: 3
  • Mole Snacks: +0/-0
Reaction of A,B steroid ring lactone with grignard reagent
« on: December 05, 2012, 03:20:14 PM »
I am having trouble with a homework problem assigned to me that is asking me to write the mechanism for the reaction of a two ring lactone with a grignard reagent.



reacts with CH3MgBr to make the product:



All I have so far is that the CH3- adds to the carbon that is double bonded with the oxygen and the pi bond from the CO double bond moves to the oxygen.  Can someone help me or guide me in the right direction?

Offline discodermolide

  • Chemist
  • Sr. Member
  • *
  • Posts: 5038
  • Mole Snacks: +405/-70
  • Gender: Male
    • My research history
Re: Reaction of A,B steroid ring lactone with grignard reagent
« Reply #1 on: December 05, 2012, 03:35:39 PM »
How will this lactone react with a Grignard reagent.
Try writing out the reaction with cyclic lactone  like tetrahydro-2H-pyran-2-one and you may see.
Development Chemists do it on Scale, Research Chemists just do it!
My Research History

Offline orgopete

  • Chemist
  • Sr. Member
  • *
  • Posts: 2636
  • Mole Snacks: +213/-71
    • Curved Arrow Press
Re: Reaction of A,B steroid ring lactone with grignard reagent
« Reply #2 on: December 05, 2012, 04:14:15 PM »
Hint, the final product is an aldol condensation product of a methyl ketone and a cyclohexanone.
Author of a multi-tiered example based workbook for learning organic chemistry mechanisms.

Offline TheAlbatross58

  • New Member
  • **
  • Posts: 3
  • Mole Snacks: +0/-0
Re: Reaction of A,B steroid ring lactone with grignard reagent
« Reply #3 on: December 05, 2012, 04:36:27 PM »
Hint, the final product is an aldol condensation product of a methyl ketone and a cyclohexanone.

That helps a lot I just cant seem to find a way to get past this stage:



I added the CH3- to the C=O carbon but there just seem to be too many electrons in there and I am really confused.

Offline discodermolide

  • Chemist
  • Sr. Member
  • *
  • Posts: 5038
  • Mole Snacks: +405/-70
  • Gender: Male
    • My research history
Re: Reaction of A,B steroid ring lactone with grignard reagent
« Reply #4 on: December 05, 2012, 04:43:34 PM »
Move the negative charge back towards the ring to re-form a carbonyl C=O, and at the same time break the bond linking the ring oxygen to the new formed carbonyl and see what you get.
Development Chemists do it on Scale, Research Chemists just do it!
My Research History

Offline TheAlbatross58

  • New Member
  • **
  • Posts: 3
  • Mole Snacks: +0/-0
Re: Reaction of A,B steroid ring lactone with grignard reagent
« Reply #5 on: December 05, 2012, 11:57:14 PM »
I got that far but I don't see how the newly formed O- will turn into the other ketone with the double bond being right there. Maybe I'm just not thinking clearly.

Offline orgopete

  • Chemist
  • Sr. Member
  • *
  • Posts: 2636
  • Mole Snacks: +213/-71
    • Curved Arrow Press
Re: Reaction of A,B steroid ring lactone with grignard reagent
« Reply #6 on: December 06, 2012, 12:10:25 AM »
You can use water as it is present from the aldol condensation.
Author of a multi-tiered example based workbook for learning organic chemistry mechanisms.

Offline discodermolide

  • Chemist
  • Sr. Member
  • *
  • Posts: 5038
  • Mole Snacks: +405/-70
  • Gender: Male
    • My research history
Re: Reaction of A,B steroid ring lactone with grignard reagent
« Reply #7 on: December 06, 2012, 01:17:32 AM »
I got that far but I don't see how the newly formed O- will turn into the other ketone with the double bond being right there. Maybe I'm just not thinking clearly.


When you do this electron movement you get an enol, which is nothing other than a carbonyl in disguise.
See picture.
Now you can perhaps understand Orgopete's first answer.
Development Chemists do it on Scale, Research Chemists just do it!
My Research History

Sponsored Links