Allenylzirconium reagents

In a process analogous to that described for allenyltitanium compounds, Cp2Zr reacts with propargylic ethers to afford allenylzirconium reagents [126], In situ additions to aldehydes yield mixtures of propargylic and allenic adducts A and B with the former predominant (Table 9.64). The anti adduct A is the major propargylic product of these additions. 

Table 9.64 In situ formation of allenylzirconium reagents and addition to aldehydes.

Allenylzirconium reagents.4 Cp2Zr reacts with propargylic ethers to form an allenylzirconium reagent (a) that reacts in situ with aldehydes in the presence of Bl etherate to form anti-i8-acetylcnic alcohols as the major product. In addition to the syn-and -acetylenic alcohols, a significant amount of an a-allenic alcohol is usually... 

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