Cyrax (Stranger)
08-31-01 11:29
No 209053
      PCP from N-benzoyl piperidine  Bookmark   

I have a little (theoretical) problem with the synthesis
of PCP from N-benzoyl piperidine.  After having done some
stoichiometry, I am demanding myself why they use 0,2 mol
excess of the grignard reagens.  After the first CH2MgBr
adds to the carbonyl, an intermediate will be formed that
has an hydrogen in alfa position, and because of this there
will be an elimination of HOMgBr so that the enamine will be formed (check it out: March, Advanced Organic Chemistry, 5 th ed., p 933).  Then I suppose that the proton of HOMgBr
adds to the alfa carbon so that an iminium salt is formed with the OMgBr counterion.  The second CH2MgBr adds then to close the cyclohexane ring.
And then, whats the big deal?
Well, if there is an excess of grignard reagens, the grignard will react with H of HOMgBr.  Isn't that a problem?
Why not use equimolar quantities?

Has someone out there experience with this reaction?
Can someone send me an electronic version of the patents?

Thx bees
(Stoni's sexual toy)
08-31-01 13:47
No 209110
      Re: PCP from N-benzoyl piperidine  Bookmark