Intermolecular chemistry of a cyclopropylcarbene and its mechanistic implications

Article abstract of DOI:10.1016/0040-4039(96)01906-5

Trans-3-(2-tert-butylcyclopropyl)-3H-diazirine was decomposed both thermally (100°C) and photochemically (350 nm, -25 to 25°C) to give the anticipated ring-expanded 3-tert-butylcyclobutene product (50% photochemical, 64% thermal), along with azine and products of trapping by solvent. In the presence of tetramethylethylene (TME), a bicyclopropyl adduct was formed in yields as high as 37% (thermal) or 32% (photochemical). The yield of 3-tert-butylcyclobutene product, however, is only very slightly (0-7%) decreased upon increasing the concentratin of TME. Similar results were obtained with propylamine as the carbene trapping agent. The response of the product mixture to changes in the concentration of the trapping agent shows that there are two product-forming pathways. The mechanistic implications of these observations are discussed.