| Abstract
| - Diazo decomposition of steroidal diazoacetates, where the point of attachment is the 3-position ofthe steroid A-ring, catalyzed by chiral dirhodium(II) carboxamidates results in products fromcarbon−hydrogen insertion in high yield and selectivities. Use of S-configured catalysts shows adistinctive preference for insertion into the 3-position to form β-lactone products. The R-configuredcatalysts direct insertion preferentially to the equatorial C−H bond at the 2-position. Substituentsor functional groups at the 5/6-position prevent C−H insertion from taking place at the 4-position.Even in the best case with the 5/6-positions fully saturated, however, insertion into the 3-positionremains competitive with insertion into the 4-position. Corresponding 3-substituted phenyldiazoacetates give only β-lactone products, and selectivity here is highest with chiral dirhodium(II)prolinate catalysts. A model is presented to explain these results. Overall, this methodology isversatile for functionalization of the steroid A-ring at positions 2 and 3.
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