Piperidines 4-subst

Some radiolysis of the piperidine ring of 28, R = H was observed during the post-y-irradiation storage of PP under accelerated test condition [227], Formation of a nitrone 146 and open-chain nitroso- 144 and nitrocompounds 145 was reported (Subst. = an ester group as in 28). 

R,R = Cl, OH, NH, subst. amino-groups, alkoxy, phenoxy, morpholine, piperidine R, R = NH, subst. amino, alkoxy, phenoxy, morpholine, piperidine... 

Ring-opening addition reactions take place between various nucleophilic reagents and a series of cyclopropanes subst. at one G-atom by 2 electron-withdrawing groups. — E A mixture of diethyl cyclopropane-1,1-dicarboxylate and 2 moles piperidine heated 20 hrs. at 102° diethyl 2-(piperidino) ethyl-malonate. Y 73%. F. e. s. J. M. Stewart and H. H. Westberg, J. Org. Ghem. 30, 1951 (1965). 

N-Subst. pyrrolidines. A 10 M soln. of BH3-dimethyl sulfide in THF added dropwise via syringe to a soln. of startg. succinamic ester in the same solvent under N2, the mixture refluxed 7-9 h, and quenched with methanol and 2 N NaOH N-phenylpyr-rolidine. Y 82%. The method failed for highly hindered amines. F.e. incl. N-subst. piperidines s. M.C. Venuti, O. Ort, Synthesis 1988, 985-8 review of pyrrole, pyrrolidine, piperidine, pyridine and azepine alkaloids (1986-7 literature) s. A.R. Pinder, Nat. Prod. Reports 6, 67-78 (1989). 

An equimolar mixture of 2-methyl-2-,3-epoxypentane, piperidine, and phenol heated 40 hrs. at 140°, and the product isolated as the hydrochloride —2-methyl-3-piperidinopentan-2-ol hydrochloride. Y ca. 100%.—The direction of ring opening is unaltered by the presence of phenol and involves attack at the least subst. C-atom of the epoxide ring. F. e. s. T. Colclough, J. I. Cunneen, and C. G. Moore, Tetrahedron 15, 187 (1961). 

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