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[摘要]：Various steroid analogs were synthesized by Stille coupling of bicyclo[4.3.0]nonenylstannanes cis-/trans-I and II with cyclohexenol triflates III (R2 = OCH2CH2O; R = H) and subsequent Diels-Alder reactions of the resulting dienes. The enantiomerically pure bicyclo[4.3.0]nonenylstannanes cis- and trans-I were prepd. in good yields via the corresponding enol triflates, obtained from the bicyclo[4.3.0]non-2-en-3-one IV. The alkenylstannane II was obtained from a [2+2] cycloadduct produced from addn. of dichloroketene to the enantiomerically pure and protected bishydroxycyclohexadiene V (65%). Stille couplings provided the tricyclic dienes in good yields (73-77%). Diels-Alder reactions with various reactive dienophiles yielded novel steroidal compds. with complete diastereoselectivity. Less reactive dienophiles required higher temps. to promote the relevant cycloaddn. Arom. B-ring steroids VI (R1 = H) (69%) and VI (R12 = bond) (5%) were accessed by dehydrogenation of with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. |
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