Alkylation

Alkylation Подпись: Base Подпись: Рік ©.Ph if Г ► "yJ* Ph (166) Scheme 31 Подпись: Рік H3<A .Ph а У сизі t N^N Ph

The alkylation of formazan anions (166) with methyl iodide yields the A-methylformazan (202) which cannot be prepared by direct methods (Scheme 31).4 However, formazans that contain hydroxyaryl (203) or heterocyclic groups (205) alkylate preferentially on these groups to yield the alkylation products 204349 and 206,346-348 respectively (Eqs. 24,25). Although formazans are resistant to acylation,334,350,351 it can be accom-

Alkylation

plished with acetic anhydride in the presence of zinc chloride.13’21’27’334 2-Amino-l,5-diphenylformazan (200) is also resistant to acylation with acetic anhydride under mild conditions; however, on heating, the tetrazole (208) is obtained, through acylation of the hydrazo nitrogen (207) (Scheme 32).28 By contrast C-hydroxyalkyl formazans (209) react with acetic anhy­dride to form the expected 0-acetyl derivative.351

Alkylation

Scheme 32

Alkylation

Alkylation

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