For a study of the retrogression of the Diels-Alder reaction in mass spectrometer we needed a series of substituted bicyclo [4, 3, 0]-3-nonenes and bicyclo [4, 3, 0]--3, 7-nonadienes with a defined annelation of the rings. In this paper we described the synthesis of derivatives with a substituent in the position C (8). As starting substances, both in the cis and in the trans series, bicyclo [4, 3, 0]--3-nonene-8-ones (IVa, b)(ref. 1, 2) and methyl bicyclo [4, 3, 0]-3- ...
