Cycloproparenes: Approaches to cyclopropa[c]furan

Treatment of 6,6-dichloro-3-oxabicyclo[3.1.0]-hexane (7) with potassiumt-butoxide generates the ring-strained cyclopropene8 as a reactive intermediate. With 1,3-diphenylisobenzofuran compound8 is trapped as a 51 mixture of theexo- andendo-adducts11a and11b, respectively. With furan only the ring expanded vinylcarbene12 is intercepted and spirocycle13a is formed. Carbene12 is also captured by cyclohexene, 2,3-dihydrofuran, 2,5-dihydrofuran, and diphenylethyne to give22–25 respectively. A likely side product in these reactions is the pyran14.On leave from Petrolite Corporation, St. Louis, MO, USA.Taken in part from a lecture delivered at the International Chemical Congress of Pacific Basin Chemical Societies, Honolulu, December 1989 (Pacifichem '89); Abstract ORGN 016. A preliminary report was communicated (see ref. [13]).