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Reaktionen von (I) mit Na‐Arensulfonylamiden und N,N‐Dichlor‐arensulfonylamiden (Molverhältnis 2:2:1) liefern die Amide (II).

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The reaction of tert-butyl 4-oxopiperidine-1-carboxylate dimethylhydrazone with BuLi and further with iodides of protected alcohols ICH 2 (CH 2 ) n OSiMe 2 (t-Bu) (n = 1-4) led to the formation of the corresponding tert-butyl 3-{[tert-butyl(dimethyl)silyl]alkyl}-4-oxopiperidine-1-carboxylates that under the treatment with triethylsilane in the presence of anhydrous BiBr 3 underwent cyclization with a high stereoselectivity into cis-isomers of N-Boc piperidine derivatives [3,2-c]-fused with oxygen heterocycles. The latter at the treatment with anhydrous HCl eliminate the Boc group affording hydrochlorides of stereochemically homogeneous N-unsubstituted fused bicyclic systems.Among the most important fields of modern organic chemistry the stereoregular synthesis should be mentioned of substances containing pharmacophore fragments of naturally occurring compounds [1, 2] that may possess a high biological activity. Among such fragments piperidine derivatives and oxygen heterocycles are often found [3], thus stimulating the research on these classes of compounds.In extension of research [4,5] on the synthesis of piperidine derivatives containing tetrahydrofuran rings we developed in this study a general stereoselective procedure for the synthesis of oxygen heterocycles [3,2-c]-fused with the piperidine ring. The protocol of the synthesis consisted in the reaction of tert-butyl 4-oxopiperidine-1-carboxylate dimethylhydrazone (I) with available [6-13] iodides of protected alcohols IIа-IId analogously to the concisely described procedure [14] (Scheme 1).In contrast to dimethylhydrazone I we failed to alkylate N-Boc-4-oxopiperidine with the formation of target products III and IV.