3-Thienylzinc halides

A useful technique for the preparation of n and Cu powders) is by electrolysis with puls< efficiency in allylation achieved by using s involves reduction of ZnCl with Na in liquid 1 Ketones. Rieke zinc produced by the r reacts with alkyl halides, and the organozin treatment with CuCN and acid chlorides. S readily prepared in this direct manner. a-Chkj method using chloroacetyl chloride in the couf 3-Thienylzinc halides. These reagenii Rieke zinc. They undergo Ni-catalyzed coupln... 

The palladium(0)-catalysed coupling of 2-bromocyclopentene-l-carboxaldehyde NJf-dimethylhydrazone with vinylzinc-, 2-furyl-, or 2-thienylzinc halides provides a route to the corresponding dimethylhydrazones, which cyclize thermally to pyridines, e.g. 9 <95T(51)9119>. 

The palladium-catalyzed reaction of 2-bromocyclopentene-l-carbaldehyde derivatives with vinylzinc, 2-furyl, or 2-thienylzinc halides leads to the dimethylhydrazones which cyclize thermally to pyridines (Scheme 97) <1995T9119>. Palladium-catalyzed hetero-annelation reactions of internal alkynes to pyridines were reported... 

This last electrochemical process is carried out in an undivided electrolysis cell fitted with a sacrificial magnesium anode and a nickel foam as cathode. The reaction is conducted in dimethylformamide in the presence of both NiBr2(bpy) as the catalyst and dried ZnBr2 (1.1 molar equivalents with respect to bromothiophene), which is used both as supporting electrolyte and as a zinc(II) ion source. The other conditions are the same as those described in the section concerning the aromatic halides. The yield of 3-thienylzinc bromide was roughly 80%, as determined by GC analysis after treatment with iodide (equation 34). 

Thienylzinc haUdes. These reagents are obtained from 3-thienyl halides and Rieke zinc. They undergo Ni-catalyzed coupling with aryl iodides. 

Thienylzinc iodides can be prepared from iodothiophenes by treatment with activated zinc on graphite. These can be transmetalated with CuCN 2LiCl and reacted subsequently with an allylic halide, or acylated with acid chlorides <94TL1047>. 

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