A protocol for the direct synthesis of azepines using a hafnium(III)-catalyzed [6 + 1] annulation of N-tethered ynenitriles with Reformatsky reagents is reported. A broad range of 3-amino-2,7-dihydro-1H-azepine-4-carboxylates 4aa-4he were obtained in high yields and with excellent functional group tolerance. The copper-mediated reactions of isolable Blaise intermediates (enamino esters 3), uniquely underwent 5-endo cyclization to afford the β-2,5-dihydropyrrolyl α,β-unsaturated esters 5aa-5fc, which exhibit anticancer activity.

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5-Acetamido-3,5-dideoxy-~-arabino-2-heptulosonic acid derivativesand analogs (shorter carbon-chain analogs of N-acetylneuraminic acid) were synthesized. Periodate oxidation followed by sodium borohydride reduction and 2-acetylation of methyl [2-(trimethylsilyl)ethyl 5-acetamido-3,5-dideoxy-g~ycero-a-~-galacto-2-nonulopyranosid)onate (3) , prepared by condensat ion of the 2-$-chloro derivative of pentaacetylneuraminic acid methyl ester (1) with trimethylsilylethanol and subsequent 2-deacetylation, gave methyl (trimethylsilylethyl 5-acetamido-4,7-di-~-acetyl-3,5-dideoxy-~-~-arabino-2-heptu1opyranosid)onate (4). Starting from compound 4, the 7-bromo, 2-a-chloro, and 2-p-thio analogs were synthesized.