The Hive => Methods Discourse => Topic started by: Cyrax on August 31, 2001, 11:29:00 AM
Title: PCP from N-benzoyl piperidine
Post by: Cyrax on August 31, 2001, 11:29:00 AM
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
Title: Re: PCP from N-benzoyl piperidine
Post by: Osmium on August 31, 2001, 01:47:00 PM