Synthesis of Piperazines and Thiomorpholines by Ozonolysis of Cyclic Olefins and Reductive N-Alkylation

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Ozonized l-trifluoroacetyl-3-pyrroline (2a) and 3-sulfolene (6) were reduced with sodium cyanoborohydride (1) to afford the dialdehyde, which reacted in situ with the primary amines 3a-d in the presence of 1 to give the piperazines 4a-d (21-60%) and the dioxothiomorpholines 7a-d (26-76%). Reduction of 7a and 7c with diisobutylaluminum hydride yielded the thiomorpholines 8a and 8c, respectively. On the other hand, the 9-membered azacrown ethers 10 and 11 were obtained when N, N'-dibenzylethylenediamine (9) was employed. The dioxothiomorpholine derivatives 13 of amino acids were also prepared by the same treatment.