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Oxidation of ethano-Troeger bases (I) and (III) with DDQ in wet nitromethane results in a highly enantiospecific methylene extrusion to afford ring contracted products (II) and (IV) which are significantly more configurationally stable than regular Troeger bases. |
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A novel CH2-extrusion reaction leading to the transformation of ethano-Tröger bases into disubstituted methano derivatives is reported (yields up to 93 %). Under mild and metal-free oxidative conditions, a loss of CH2 and a ring contraction are provoked. Despite two bond cleavages at stereogenic nitrogen and carbon centers and a temporary rupture of the bicyclic structure, a very high enantiospecificity (es≥98 %) is observed for this unusual reaction. |