A Novel Hydrazine Linker Resin and Its Application for the Solid-Phase Synthesis of α-Branched Primary Amines

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Abstract
A novel hydrazine linker resin for solid-phase organic synthesis has been developed. Starting from Merrifield resin, the new N-butyl-N-methylpolystyrene-hydrazine linker is prepared in three steps. Polymer-supported hydrazones, readily prepared from aldehydes and the hydrazine resin, react with alkyl- and arylorganolithium reagents under 1,2-addition to the C-N double bond to afford the corresponding hydrazines. Release from solid support was achieved by reductive N-N bond cleavage using the borane-tetrahydrofuran complex. The resulting alpha-branched primary amines were protected as their amides or carbamates, respectively, and, after purification, were obtained in good overall yields and in high purity (12 examples).