o‐Alkoxyphenyliminoiodanes: Highly Efficient Reagents for the Catalytic Aziridination of Alkenes and the Metal‐Free Amination of Organic Substrates

Abstract

Within the rapidly growing field of hypervalent iodine chemistry, [1] iminoiodanes occupy a special and important place. N-Tosyliminoiodanes, ArINTs, have found a broad range of synthetic applications as useful nitrene precursors under thermal or catalytic conditions in the aziridination of alkenes and the amidation reactions of various organic substrates. [1d,e, 2] Representative recent examples of the synthetic use of PhINTs include the highly efficient Ru II -or Cu I -catalyzed CÀH-bond amidation of aldehydes, [2a,b] the gold-catalyzed nitrene transfer and CÀH insertion reactions, [2c,d] the silver-catalyzed C À H insertion and aziridination reactions, [2e,f] and numerous asymmetric aziridinations of alkenes by using copper catalysts with chiral dinitrogen ligands. [2g-l] However, despite its importance, PhINTs is not a perfect reagent and has a serious drawback: it is insoluble in most organic solvents due to its strong intermolecular secondary bonding that creates a three-dimensional polymeric structure.[1d,e, 3a-c] Several research groups have tried to improve the synthetic potential of iminoiodanes by developing new reagents or reagent combinations.[1e, 3d-h] A particularly fruitful approach to soluble iminoiodanes is based on the placement of an ortho-tert-butylsulfonyl group onto the iodobenzene ring of the parent PhINTs.[3d-f] Thus, several ArINTs (Ar = 2-tBuSO 2 C 6 H 4 , 2-tBuSO 2 -5-tBuC 6 H 3 , and 2-tBuSO 2 -4-CF 3 C 6 H 3 ) have been synthesized and utilized as soluble nitrene precursors, the reactivity of which is similar to the parent PhINTs. The solubility of these reagents is explained by the presence of intramolecular I···O secondary bonds due to the ortho-sulfonyl substituent, which redirects the intermolecular I···O and I···N secondary bonds responsible for the polymeric structure of PhINTs.[3d-f] These soluble nitrene precursors have proved to be useful reagents; [3d-f, 4] however, their preparation requires four to seven synthetic steps and their reactivity does not show any improvement relative to PhINTs.Herein, we report the preparation, structural investigation, and reactivity of new highly soluble and reactive nitrene precursors 3, which are derived from ortho-alkoxyiodobenzenes. The choice of this structural motif is based on our previous observation that the presence of an orthoalkoxy group in iodine(V) derivatives leads to the replacement of the intermolecular I···O secondary bonds with intramolecular I···O bonds and results in a significant improvement in the solubility of iodylarenes, ArIO 2 . [5] o-Alkoxyphenyliminoiodanes 3 a-d were synthesized in two simple steps starting from readily available 2-iodophenol ethers 1 a-d (Scheme 1). In the first step, iodides 1 were oxidized by peracetic acid to form diacetoxyiodo derivatives 2; the structures of products 2 a and d were established by X-ray analysis.[6] In the second step, diacetates 2 were converted to iminoiodanes 3 by treatment with tosylamide under basic conditions, in methanol.Products 3 precipitated from the react...

Saccharin‐Based μ‐Oxo Imidoiodane: A Readily Available and Highly Reactive Reagent for Electrophilic Amination

“…In recent years, hypervalent iodine reagents have emerged as environmentally friendly and efficient oxidizing reagents for various synthetically useful oxidative transformations 1. Particularly important are hypervalent iodine(III) compounds with iodinenitrogen bonds,2 such as azidoiodanes,2a–e benziodazoles,2f, g amidobenziodoxoles,2j and iminoiodanes,2j–o all of which are efficient reagents for CN bond forming reactions. Representative recent examples of synthetic applications of these reagents include direct azidation, amination, imidation, aziridination, metal‐catalyzed imidation, and CH insertion reactions 2.…”

Photoactivated N‐Acyliminoiodinanes Applied to Amination: an ortho‐Methoxymethyl Group Stabilizes Reactive Precursors

“…Interestingly,t he distance between the iodine atom of 3c and the carbonyl oxygen atom of the N-trifluoroacetyl group was also within the sum of the Va n der Waals radii, and 3c was obtained as am onomeric structure with no obvious intermolecular interactions; contrary to the previously reported X-ray structures of N-sulfonyliminoiodinanes. [6][7][8] TheN ÀIb ond length was 2.050 ,w hich is almost identical to that of N-iodosuccinimide (2.059 ), [22] and slightly longer than that of N-sulfonyliminoiodinanes (1.990-2.039 ). [6][7][8] Based on the X-ray structure of 3c,n atural population analysis was performed at the MP2/6-311 + G(d,p) level [23] using Gaussian 09.…”

“…[3,4] Because of their poor solubility in organic solvents,d erivatization to am ore soluble form by introducing an ortho-coordinating substituent has been developed. [5] As representative examples,i minoiodinanes bearing ortho-sulfonyl, [6] alkoxy, [7] and methoxymethyl [8] substituents,d eveloped by Protasiewicz, Zhdankin, and Woodward, respectively (Scheme 1a), improved the solubility,a nd those structures were successfully characterized by X-ray analyses.H owever,m ost of the reported N-protecting groups are limited to N-sulfonyl groups,s uch as tosyl and nosyl groups,a nd only one report has been made on the synthesis and reactivity of an N-acyliminoiodinane;p resumably because of their lability toward Hofmann rearrangement and/or hydrolysis. [9] In fact, although N-trifluoroacetyliminoiodinane 3a has been synthesized and reacted with an alkene under iron catalysis, 3a was reported to be unstable, [10] and the corresponding aziridine was only obtained in approximately 50 %y ield.…”

Metal‐Free [2+2+1] Annulation of Alkynes, Nitriles and Nitrogen Atoms from Iminoiodanes for Synthesis of Highly Substituted Imidazoles

“…Under transition metalcatalyzed conditions, PhINSO 2 R [12] has been well known to serve as an excellent nitrenoid precursor in the aziridination of alkenes, [13] the C À H amidation of alkanes, arenes and aldehydes, [14] and so on. [15] Very recently, it has been reported that ArINSO 2 R medi-ates the aziridination of alkenes [16] and C À H amidation of aldehydes and 1,3-dicarbonyl compounds [17] without any metal catalyst. To the best of our knowledge, however, multicomponent reactions with PhINSO 2 R have not been achieved.…”