Brønsted acid-promoted aziridination of electron-deficient olefins

A combined theoretical and experimental approach was used to systematically study the Brønsted acid-promoted aziridination of electron-deficient olefins. It was found that Brønsted acid-promoted aziridination of electron-deficient olefins proceeded through the attack of the internal nitrogen of the azide to the terminal carbon of protonated olefin, which afforded an acyclic adduct that subsequently discharged N₂ to produce the aziridine ring. The basicity of the electron-deficient olefins is an important parameter to determine the efficiency of Brønsted acid-promoted aziridination. More basic carbonyl compounds including vinyl ketones and acrylamides were predicted to be readily activated by Brønsted acid such as TfOH, whereas less basic carbonyl compounds were predicted to be poor substrates. Significantly, all these theoretical predictions were demonstrated to be consistent with the experimental data. Furthermore, a systematic evaluation of TfOH-promoted aziridination of acrylamides was performed, which established a new, single-step method for the preparation of a number of aziridine-2-carboxamides.     

Synthesis and structure of hypervalent diacetoxybromobenzene and aziridination of olefins with imino-λ3-bromane generated in situ under metal-free conditions

Ligand exchange of p-CF(3)C(6)H(4)BrF(2) with acetoxy groups using AcOH and Ac(2)O affords (diacetoxybromo)benzene in a high yield, which undergoes aziridination of alkenes in the presence of TfNH(2) and sulfamate esters in one pot under mild conditions. The aziridination with TfNH(2) proceeds stereospecifically with retention of stereochemistry of olefins at room temperature using limiting amounts of olefins under transition-metal-free conditions. The one-pot aziridination procedure using sulfamate esters can be applied to the intramolecular versions.     

Investigations in the transition metal catalyzed aziridination of olefins, amination, and other insertion reactions with Bromamine-T as the source of nitrene.

Investigations into the transition metal catalyzed aziridination of olefins with Bromamine-T as a new source of nitrene is presented in this account. Comparison of Chloramine-T and Bromamine-T in this reaction indicates that the latter is superior as the source of nitrene. Systematic study with several transition metal based catalysts suggests that Cu-halides are the best catalysts. A first report of aziridination under microwave and ultrasound irradiation conditions is also presented. Copper-catalyzed aziridination of methyl cinnamate with Bromamine-T did not proceed at ambient temperature but was effected smoothly under ultrasound irradiation to furnish trans-aziridine selectively, while under microwave irradiation, a mixture of cis and trans isomers, was obtained. It has been demonstrated that aziridination of olefins proceeds smoothly with inexpensive bleaching powder. Preliminary results of Rh-catalyzed benzylic insertion reactions with Bromamine-T are included in this account.     

Asymmetric olefin aziridination using a newly designed Ru(CO)(salen) complex as the catalyst

Highly enantioselective and good to high-yielding aziridination of conjugated and non-conjugated terminal olefins and cyclic olefins was achieved using a newly designed Ru(CO)(salen) complex as the catalyst in the presence of SESN(3) under mild conditions.     

Iron(III) porphyrin catalyzed aziridination of alkenes with bromamine-T as nitrene source

[reaction: see text] Iron(III) porphyrin complexes Fe(Por)Cl are effective catalysts for aziridination of alkenes using bromamine-T as the nitrene source. The catalytic system can operate under mild conditions with alkenes as limiting reagents. The aziridination reaction is general and suitable for a wide variety of alkenes, including aromatic, aliphatic, cyclic, and acyclic olefins, as well as alpha,beta-unsaturated esters. For 1,2-disubstituted olefins, the reactions proceeded with moderate to low stereospecificity.     

Practical aziridinations II: electronic modifications to poly(pyrazolyl)borate-copper catalysts

A significant influence of the electronic features of poly(pyrazolyl)borate ligands on the efficiency of the copper-catalyzed aziridination reaction has been noted. Electron-deficient, bidentate di(pyrazolyl)borates in conjunction with copper(II) chloride generated the most effective catalyst system for the aziridination of a variety of olefins.     

Efficient aziridination of olefins catalyzed by a unique disilver(I) compound

A unique disilver(I) compound is an efficient catalyst for aziridination of olefins.     

氮杂环丙化反应研究的新近进展

综述了近几年氮杂环丙化反应研究工作的进展, 重点介绍了乃春与烯烃的转换, 卡宾与N＝C的转换以及不同反应底物官能团转换的合成策略.     

Schiff base过渡金属配合物在不对称催化中的应用

综述了Ｓｃｈｉｆｆｂａｓｅ过渡金属配合物在不对称催化烯烃环氧化、氮杂环丙烷化、环丙烷化和其它催化反应中的应用研究进展，参考文献３９篇。     

Copper(I)-catalyzed asymmetric alkene aziridination mediated by PhI(OAc)2: a facile one-pot procedure

A facile one-pot procedure for copper-catalyzed PhI(OAc)₂-mediated asymmetric alkene aziridination had been developed. Commercially available PhI(OAc)₂ and sulfonamides were used to generate the nitrene precursors (PhINR) in situ for olefin aziridination. This one-pot procedure had been optimized using 4-nitrobenzenesulfonamide as the nitrene source. With 5 mol % of the chiral copper catalyst, these conditions afforded 94% yield of the isolated product with 75% ee. We had also developed a simple and rapid method to monitor the rate of this one-pot aziridination.     

Non-heme iron(II) complexes are efficient olefin aziridination catalysts

Iron(II) complexes of polydentate nitrogen donor ligands catalyze the rapid aziridination of olefins by PhINTs.     

Copper-nitrenoid formation and transfer in catalytic olefin aziridination utilizing chelating 2-pyridylsulfonyl moieties

We have developed an efficient protocol for copper-catalyzed olefin aziridination using 5-methyl-2-pyridinesulfonamide or 2-pyridinesulfonyl azide as the nitrenoid source. The presence of a 2-pyridyl group significantly facilitates aziridination, suggesting that the reaction is driven by the favorable formation of a pyridyl-coordinated nitrenoid intermediate. Using this chelation-assisted strategy, synthetically acceptable yields of aziridines could be obtained with a range of aryl olefins even in the absence of external ligands. Importantly, a large excess of olefin is not required. X-ray crystallography, ESI-MS, Hammett plot analysis, kinetic studies, and computational undertakings strongly support that the observed aziridination is driven by internal coordination.     

Chiral rhodium(II,II) dimers catalyzed enantioselective intramolecular aziridination of sulfonamides and carbamates

The asymmetric intramolecular aziridination of unsaturated sulfonamides and carbamates catalyzed by chiral dirhodium(II,II) complexes were achieved in good yields (up to 95%) and enantioselectivity (up to 76% e.e.).     

手性双唑啉铜配合物在不对称合成中的应用

综述了手性双E唑啉配体的主要结构类型,并讨论了手性双E唑啉铜配合物在不对称Diels-Alder反应、Ene反应、Mukaiyama adol反应、烯丙基氧化、环丙烷化、氮杂环丙烷化等反应中的应用。     

Catalytic stereoselective alkene aziridination with sulfonimidamides

Diastereoselective copper-catalyzed alkene aziridination has been investigated using chiral nitrenes generated from sulfonimidamides in the presence of an iodine(III) oxidant. Starting from a stoichiometric amount of the substrates, the corresponding aziridines were isolated with excellent yields of up to 96%. Good levels of asymmetric induction were obtained in the case of electron-poor olefins, with an optimal de of 94% being reached starting from tert-butyl acrylate. Matching and mismatching effects were also observed upon the use of chiral copper catalysts for the aziridination of styrene.     

金属络合物催化剂在不对称氮杂环丙烷反应中的研究进展

不对称氮杂环丙烷化;手性催化;金属络合物催化剂在不对称氮杂环丙烷反应中的研究进展     

Catalytic aziridination of olefins and amidation of thioanisole by a non-heme iron complex

A non-heme iron complex catalyses the aziridination of various olefins and the amidation of thioanisole in good yields at the expense of an aryl iodinane.     

碘作为催化剂在有机合成中的应用

综述了单质碘作为催化剂在有机合成中的应用研究. 碘催化的反应主要涉及醚的去保护基, 酯化和酯交换反应、缩醛(酮)的形成、亲电取代反应、烯烃的氮杂环丙烷化、烯糖的糖苷化反应等.     

Unprecedented Trinuclear AgI Complex with 2,4,6‐Tris(2‐pyrimidyl)‐1,3,5‐triazine as an Efficient Catalyst for the Aziridination of Olefins

An unprecedented trinuclear heteroleptic Ag^I complex was isolated using a stable multidentate 2,4,6‐tris(2‐pyrimidyl)‐1,3,5‐triazine (TPymT) ligand. The obtained compound is an efficient catalyst for the direct aziridination of terminal olefins.     

Rhodium(II)-catalyzed aziridination of allyl-substituted sulfonamides and carbamates

Several unsaturated sulfonamides underwent intramolecular aziridination when treated with PhI(OAc)(2), MgO, and catalytic Rh(2)(OAc)(4) to give bicyclic aziridines in excellent yield. Treatment of the resulting azabicyclic sulfonamides in methanol in the presence of p-TsOH resulted in exclusive opening of the aziridine ring at the most substituted position affording six- and seven-membered ring products in high yield. In contrast, the intramolecular aziridination of several cycloalkenyl-substituted carbamates did not require a Rh(II) catalyst and proceeded via an iminoiodinane intermediate. The resulting tricyclic aziridines underwent ring opening when treated with various nucleophiles to give anti-derived products as expected for nucleophilic attack at the three-membered ring. The iodine(III)-mediated reaction of a 3-indolyl-substituted carbamate, however, required a Rh(II) catalyst. The expected aziridine was not observed, but rather simultaneous spirocyclization of C(3) and stereoselective syn-acylation at C(2) occurred to give compound 41, whose structure was unequivocally established by an X-ray crystallographic study. The reaction proceeds in a stepwise manner via a metal-free zwitterionic intermediate which is attacked by a nucleophilic reagent on the same side of the amide anion. Related reactions occurred with both a 2-indolyl- and 3-benzofuranyl-substituted carbamate but with lower stereoselectivity.