Platinum-promoted cyclization reactions of amino olefins

The compounds 1-, 2- and 3-methylpent-4 enylamine cyclize, in a reaction medium containing [PtCl4]2-, to the corresponding cis- and trans-dimethylpyrrolidines showing marked regio and stereoselectivity effects. The following cyclization reactions are also reported: a) that of hex-4-enylamine which gives a mixture of 2-ethylpyrrolidine and 2-methylpiperidine, b) that of 2,2-dimethylpent-4-enylamine which produces 2,4,4-trimethylpyrrolidine and c) that of 2,2-dimethylhex-4-enylamine which results in the formation of 2-ethyl-4,4-dimethylpyrrolidine and 2-methyl-5,5-dimethylpiperidine. The X-ray crystal structures of trans-[PtCl2(amine)(Et3P)] (amine = cis-2, 4-dimethylpyrrolidine and cis-2,3-dimethylpyrrolidine) are reported.