Silver‐Catalyzed Intermolecular Amination of CH Groups

101

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...

Section: Methodsmentioning

confidence: 99%

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

Yoshimura

Nemykin

Zhdankin

2011

101

“…[3] These species catalytically undergo both amination of unactivated aliphatic (sp 3 ) C À H bonds and transfer of the imino groups to olefins and heteroatom nucleophiles, which include nitrogen heterocycles, sulfides, and sulfoxides. [4][5][6][7] In the absence of metal catalysts, the nitrenoid-transfer reaction of imino-l 3 -iodanes does not take place or requires harsh reaction conditions, [8] partly due to their insoluble nature in common organic media, evoked by the highly aggregated polymeric zigzag structure. [9] Recently, we reported the synthesis of Group 17 analogue trifluoromethanesulfonyliminoA C H T U N G T R E N N U N G (aryl)-l 3 -bromane (1).…”

Section: Introductionmentioning

confidence: 99%

Imination of Sulfides and Sulfoxides with Sulfonylimino‐λ³‐Bromane under Mild, Metal‐Free Conditions

Ochiai

Naito

Miyamoto

et al. 2010

Exposure of sulfides and sulfoxides to trifluoromethanesulfonylimino(aryl)-lambda(3)-bromane in dichloromethane at 0 degrees C results in a facile transfer of the sulfonylimino group to sulfur atoms and affords N-triflylsulfilimines and -sulfoximines in high yields under transition-metal-free conditions. Imination of (R)-methyl p-tolyl sulfoxide proceeded with predominant retention of configuration at the stereogenic sulfur center. The Hammett plot afforded rho values of -0.58 for para-substituted thioanisoles and -0.49 for their equivalent sulfoxides, which suggests a buildup of positive charge on the sulfur atoms of sulfides and sulfoxides in the transition state. Calculations suggest a bimolecular nucleophilic-substitution mechanism on the negatively charged nitrogen atom of the sulfonylimino-lambda(3)-bromane, which involves the attack of a sulfide from the opposite side to bromine(III).

“…However, the generation of a stoichiometric amount of iodobenzene is still a major drawback associated with the use of hypervalent iodine reagents. Amination reactions have been developed by using various metal complexes, such as Co,7b,c Ru,7a Cu,8, 9f,l,s Au,9p Ag,9i,q and Pd9m to catalyze nitrene insertion, but rhodium dimers remain the most employed complexes 9a–c,g,h,j,k,n,o,r,t. With all these methods in hand, intramolecular CH insertion is now an established reaction that is used in total synthesis to form β‐ or γ‐amino alcohols 11.…”

Section: Introductionmentioning

confidence: 99%

N‐Tosyloxycarbamates as Reagents in Rhodium‐Catalyzed CH Amination Reactions

Huard

Lebel

2008

173

Metal nitrenes for use in C-H insertion reactions were obtained from N-tosyloxycarbamates in the presence of an inorganic base and a rhodium(II) dimer complex catalyst. The C-H amination reaction proceeds smoothly, and the potassium tosylate that forms as a byproduct is easily removed by filtration or an aqueous workup. This new methodology allows the amination of ethereal, benzylic, tertiary, secondary, and even primary C-H bonds. The intramolecular reaction provides an interesting route to various substituted oxazolidinones, whereas the intermolecular reaction gives trichloroethoxycarbonyl-protected amines that can be isolated with moderate to excellent yields and that cleave easily to produce the corresponding free amine. The development, scope, and limitations of the reactions are discussed herein. Isotopic effects and the electronic nature of the transition state are used to discuss the mechanism of the reaction.