[b] Isolated yield of product 9s [c] Ratios of mono to bis-3,5-isoxazole determined by the integration of the crude 1 H-NMR. To further expand the chemical space and exploit the formation of a carbon-carbon bond (C1-C2) resulting from the cycloaddition, we investigated the N-O bond reduction of the isoxazole to access a β-ketoenamine-alkyne derivative (Scheme 4). Although βketoenamine motifs are encountered in natural products, materials, and are versatile intermidiates, there are no reports of β-ketoenamine-alkynes. We studied the reduction of 3,5isoxazole-alkyne (9e) using Mo(CO)6, a conventional reducing agent for isoxazoles. We found that N-O reduction to obtain β-ketoenamine (12) occurs in excellent yields when performing the reduction at 90 °C and using 1.5 equivalents of Mo(CO)6 (Scheme 4). This route achieves a convenient method to access β-ketoenamines with an alkyne handle that can be further modified as required.