The formation of the stable form of 1-azabicyclo[4.1.0]heptane tosylate was successfully achieved from 2-[4-tolenesulfonyloxybutyl]aziridine, by stirring in MeCNa t room temperature. The ring strain in the three-membered ring could be released through the cleavageo fe ither CÀN bond, but ring opening with various nucleophilesproceeded in ah ighly regio-ands tereoselective manner.T wo possible pathways, in which the aziridine ringw as opened by nucleophilic attack at the bridge and the bridgehead, yielded piperidine and azepane rings, respectively.T his selective transformation starting from chiral aziridines constitutes an efficient route for the asymmetric synthesis of biologically importantn atural products, such as fagomines,f ebrifugine, sedamine, hydroxypipecolic acid, and balanol.

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Gold(III) chloride is found to be an effective catalyst for the addition of alkynes on activated quinoline/isoquinolines to produce a series of alkynyl-substituted 1,2-dihydroquinolines and isoquinolines in a single-step operation. The easy availability of starting materials, convenient synthetic procedure, operational simplicity, and high regioselectivity makes this strategy very useful for the preparation of enyne derivatives of aza-aromatic compounds.

A divergent, new, and highly stereoselective synthesis of cis-2,6-disubstituted piperidine natural products including isosolenopsins, deoxocassine, and spectaline was achieved from chiral aziridine decorated with appropriate alkyl chains for isosolenopsins or alkynyl groups for deoxocassine and spectaline at C2. The characteristic feature of this synthesis is one-pot sequential reactions under atmospheric hydrogen including the reduction of alkyne (for deoxocassine and spectaline), reductive ring-opening of aziridine, debenzylation, and intramolecular reductive amination in high yields. The prerequisite aziridines were elaborated from commercially available (2S)-hydroxymethylaziridine through oxidation, Wittig olefination, and the Grignard reaction for isosolenopsins or substrate-controlled lithium alkynylate addition for deoxocassine and spectaline.