A Mild and Efficient CH2‐Extrusion Reaction for the Enantiospecific Synthesis of Highly Configurationally Stable Tröger Bases

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.