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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Synthesis of oleophilic electron-rich phenylhydrazines
Aleksandra Jankowiak1, Piotr Kaszyński
1Organic Materials Research Group, Department of Chemistry, Vanderbilt University, Nashville, TN 37235.
Abstract:
Phenylhydrazines 1 substituted with two or three long-chain alkyl, alkoxy or alkylsulfanyl groups were successfully prepared by acid-induced removal of the Boc group in hydrazides 2. The reaction is carried out with 5 equivalents of TfOH in CF(3)CH(2)OH/CH(2)Cl(2) at -40 °C for 1.5 min. Under these conditions, the deprotected hydrazine 1 is fully protonated, which increases its stability in the reaction medium. The hydrazines were isolated in 60-86% yields and purities >90%. The hydrazides 2 were obtained in 43-71% yields from aryl bromides 5, which were lithiated with t-BuLi and subsequently reacted with di-tert-butyl azodicarboxylate (DTBAD).
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