| Abstract
| - Ethyl 1-butynylphosphonate reacts with Cp2ZrCl2/2n-BuLi to give a three-membered zirconacyclethat readily inserts aldehydes. Hydrolysis of the intermediate five-membered zirconacycles leadsto two products, 4 and 5. In the major product, 5, the aldehyde inserts into C2 of the zirconacycle,while in the minor product, 4, the aldehyde inserts into C1. Products 5 are obtained in 38−75%isolated yields. Products 4 are obtained in approximately 1−12%. Essentially, only compounds 5are produced with ortho-substituted aldehydes. The regio- and stereochemistry of 4 and 5 weredetermined by 3JPH, 2JPC2, and 3JPC3 coupling constants.
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