Rearrangements of 2‐ and 3‐Furfurylidene

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Abstract
The photo‐ and thermochemistry of diazo(2‐furyl)methane (3) and diazo(3‐furyl)methane (6) was investigated using the matrix isolation technique. Photolysis of 3 results in the formation of (Z)‐pent‐2‐en‐4‐yn‐1‐al (2) in a clean reaction, in agreement with the observation of Shechter et al. Photolysis or pyrolysis of diazo compound 6 yields (s‐Z)‐(α‐formyl)methylenecyclopropene (s‐Z‐13) as the only detectable product. Carbene 14 and cyclopropene 15 are proposed as intermediates, but not stable under the reaction conditions and thus not directly observed. The reaction sequence 6→13 provides a novel and simple route to methylenecyclopropenes.