Pyrometallurgy grade zinc

Zn in these equations denotes pyrometallurgy grade zinc, containing 0.04-0.07% lead. When pure, lead-free zinc is used, a catalytic amount of PbCl2 should be added. 

On the other hand, it is not necessary to prepare such unstable gem-dihaloalkanes in advance. Esters can be alkylidenated by treatment with Zn-CH3CHBr2-TiCl4-TMEDA (Scheme 5.18) [15]. This reaction requires a large excess of the reagent. It should be noted that the zinc powder used in these procedures was also pyrometallurgy grade zinc, containing about 0.04-0.07% of lead. 

Esters were also alkylidenated by treatment with Zn (pyrometallurgy grade zinc, containing lead)-Me3SiCHBr2-TiCl4-TMEDA (Scheme 5.24) [33]. This reagent was found to convert thioesters into the vinyl sulfides. 

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See also in sourсe #XX -- [ ]

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