Cyclopropanization of Methyl Carboxylates with Tebbe ‐Type Reagents

The methylenation reaction of methyl azulene‐2‐carboxylates ( cf. Schemes 1 and 2 ) with Tebbe's or Takai's reagent is described. When the prescribed amount of Takai's reagent is applied in a four‐fold excess, the corresponding cyclopropyl methyl ethers are formed instead of the enol ethers ( cf. Schemes 2 and 3 ). Similarly, methyl benzoate and methyl 2‐naphthoate yield, after treatment with Takai's reagent and hydrolysis, the corresponding cyclopropanols 18 and 19 , respectively ( Scheme 3 ). The cyclopropyl methyl ether 4 or cyclopropanol 5 rearrange, on acid catalysis, into the l‐(azulen‐2‐yl)propan‐l‐one 20 ( Scheme 4 ). whose reduction with Et 3 SiH in CF 3 COOH yields the 2‐propylazulene 21 .