Synthesis of Methyl 1‐Formylcyclopropanecarboxylate utilizing Ti‐Claisen Condensation

Abstract α‐formylation reaction of methyl 4‐chlorobutanoate (1) is a distinctive example of the compatibility with a base‐sensitive γ‐chloro group. Synthesis of 2 is not possible using the base‐mediated α‐formylation method due to undesirable and predominant cyclopropane formation leading to methyl cyclopropanecarboxylate. In conclusion, the present straightforward and robust synthetic strategy for the unique, but useful, building block 2 utilizing Ti‐Claisen condensation provides a new promising avenue, especially for pharmaceutical syntheses.