Oxidation of Amines with Hypervalent tert-Butylperoxyiodanes: Synthesis of Imines and tert-Butylperoxyamino Acetals

Reaction of secondary amines with I-ten-butylperoxy-l.2benziodoxol-3(1H)-one (2) undergoes dehydrogenation to afford imines in the presence of K 2 a 3 .while oxidation of tertiary amines without base produces ten-butylperoxyamino acetals.Organoiodanes undergo oxidation of amines to give a variety of products depending on the type of mine.' Oxidation of primary aromatic amines with (diacetoxyiodo)benzene or [bis(mfluoroacetoxy)iodolhenzene results in formation of.trans-am compounds via oxidative coupling.2Primary aliphatic amines on oxidation with iodosylbenzene give nitriles, while primary cycloalkylamines and cyclic secondary amines in the presence of water afford cyclic ketones and lactams, respectively, via intermediate formation of the corresponding imines.kIn the absence of water, iodosylbenzene oxidation of cyclic sec-amines affords the imines:3b.cfor instance, oxidation of pyrrolidine in dichloromethane at room temperature gave quantitatively a mixture of 1-pyrroline and its cyclic mmer in a ratio 93:7.The elegant synthesis of discorhabdin C reported by Kita and coworkers involves an intramolecular oxidative spiro cyclization of silylated phenols with aminoquinone functionalities by [bis(mfluoroacetoxy)iodo]ben~ne~ Oxidations of tertiary amines with organoiodanes are limited.Magnus and coworkers have reported an interesting oxidation of tertiary amines with a combination of iodosylbenzene-mmethylsilylazide, which undergoes N-alkyl azidonation of N,N-dialkylarylamines.5 Recently, we reported the synthesis and characterization of the stable crystalline (alkylperoxy)iodane, I-ten-butylperoxy-l,2-benziodoxol-3(1H)-one (2) via the Lewis acid-catalyzed ligand exchange of I-hydroxy-1,2-benziodoxol-3(1H)-one with ten-butyl hydroperoxide in chloroform.6The peroxyiodane (2) oxidizes benzyl and ally1 ethers to the esters even at room temperature in the presence of alkali metal carbonates.7Because this reaction is compatible with other protecting groups such as MOM, THP, and TBDMS ethers, and acetoxy groups, and because esters are readily hydrolyzed under basic conditions, this method provides aconvenient and effective alternative to the usual reductive deprotection of benzyl and This paper is dedicated to the memory of the late Professor Shun-ichi Yamada.