Organozinc halides oxidation

Organozinc Halides by the Oxidative Addition of Organohalides to Zinc 329... 

The nature of the zinc (dust, foil, or shots) is important for the success of the formation of an organozinc halide by oxidative addition. Usually, the use of zinc dust (-325 mesh) from Aldrich or Riedel de Haen gives the best results. In some cases, such as for the preparation of allylic zinc halide reagents,22,28 iodomethylzinc iodide,65 or benzylic zinc halides,66 the use of zinc foil (0.1 mm or 0.25 mm thick, Aldrich or Merck) may be advantageous or even essential. 

The most significant obstacle to be overcome in the preparation of organozinc halides by direct insertion of zinc metal into an organic halide is the intrinsic lack of reactivity of commercially available zinc metal. This is primarily due to a surface coating, for example of zinc oxide, which prevents direct reaction with an organic substrate. The success of attempts to insert zinc metal into an organic halide is entirely dependent upon the care with which the zinc metal is... 

The oxidation of organozinc halides and diorganozincs is a facile radical reaction.1 It provides usually a mixture of hydroperoxides and alcohols,12 13 but through careful control of the reaction conditions it allows preparation of either new hydroperoxides or by working under reductive conditions solely alcohols.14,15 Thus, the treatment of myrtanylzinc bromide with oxygen in perfluorohexanes12,13 at -78 °C affords the desired hydroperoxide with high selectivity. This method is well suited for the preparation of polyfunctional hydroperoxides (Scheme 9.6). 

The oxidative coupling of organozinc halides was also explored in the synthesis of macrocycles. Spring and co-workers combined a copper catalyst and oxygen with organozinc reagents the coupled products were produced in high yields (Scheme 4.4). ... 

The general utility of the oxidative addition of functionalized organic halides to zinc was demonstrated by the formation of organozinc iodides 28 from protected (3- and 7-amino acids (Scheme 26).73 The organozinc iodides prepared in this manner were neither sufficiently stable nor sufficiently reactive in THF, but excellent yields were obtained in more polar aprotic solvents, such as DMF and DMSO. 

The acylpalladium is formed by CO insertion as the intermediate of the carbonylation. They can be prepared directly by the oxidative addition of acyl chlorides to Pd(0). Thus ketones can be prepared by the reaction of acyl halides with organozinc reagents and organostannanes. Benzoacetate (490) is obtained by the reaction of benzoyl chloride with the Reformatsky reagent 489 [243], The macrocyclic keto lactone 492 is obtained by intramolecular reaction of the alkenylstannane with acyl chloride in 491 [244]. 

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