A tandem Knoevenagel/hetero-Diels–Alder reaction of the aldehyde 2 with the cyclic 1,3-dioxo compound 1 and its analogues leads stereoselectively to the trans-bonded heterosteroids 3 (de > 98%). Aldehyde 2 is obtained by ozonolysis of enantiomerically pure tetrahydroindanone derivatives, which are in turn readily available by the Wiechert-Hajos procedure.
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Tietze et al. (1990) studied this question.
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