REARRANGEMENTS OF 2-FURFURYLIDENE AND 3-FURFURYLIDENE

The photo- and thermochemistry of diazo(2-furyl)methane (3) and diazo( 3-furyl)methane (6) was investigated using the matrix isolation techni que. 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 Shech ter et al. Photolysis or pyrolysis of diazo compound 6 yields (s-Z)-(a lpha-formyl)methylenecyclopropene (s-Z-13) as the only detectable prod uct. Carbene 14 and cyclopropene 15 are proposed as intermediates, but not stable under the reaction conditions and thus not directly observ ed. The reaction sequence 6 --> 13 provides a novel and simple route t o methylenecyclopropenes.