Addition of dichloromethylene carbene to alkenes

by James

Description: Treatment of chloroform (CHCl3) with strong base (NaOH) leads to the formation of a dichlorocarbene, which then can form a cyclopropane when added to an alkene.

Notes: The byproducts of this reaction are NaCl and H2O



Mechanism: Deprotonation of chloroform (Step 1, arrows A and B) leads to formation of a short-lived anion. Loss of chloride ion from this ion (Step 2, arrow C) leads to formation of a carbene. When combined with an alkene, a cyclopropane will form (Step 3, arrows D and E).

Notes: This reaction proceeds through a concerted transition state (see bottom left).



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