The Mechanism of Formation of Acenaphthylene on Pyrolysis of 8-Methylcyclobuta[a]naphthalene-1,2-dione

Abstract

Flash vacuum pyrolysis of the l-¹³C labelled title dione (13) gives acenaphthylene labelled predominantly at C4 (65.9%) and C1 (27.6%). This is in accord with the intermediacy of the (labelled) acyloxycarbene (5), the lactone (6) and the carbene (7). The minor leakage of label to C3 (5.8%) and C5 (0.7%) is discussed. Irradiation of labelled dione (13) in methanol with ultraviolet light gives 3-methoxy-9-methyl[1-¹³C] naphtho [1,2-c]furan-1(3H)-one (19).