Abstract:A ligand-controlled system has been disclosed for the regioselective palladium-catalyzed diamination of unactivated alkenes, which provides an easy access to a variety of aminofunctionalized piperidines and pyrrolidines. The steric hindrance of ligands controlled the regioselectivtities of products. 6-Endo diamination occurred with less sterically hindered quinox ligand to afford 3-aminopiperidines, while 5-exo diamination occurred with sterically bulky pyox ligand to give amino-substituted pyrrolidines.
“…After having established an efficient synthesis of αmaleimide substituted cyclic amines with piperidines and morpholines as the substrates, we were then curious about whether this new protocol could be applied for the αfunctionalization of pyrrolidines. 9 Thus, 1-phenylpyrrolidine (4a) was treated with 2a under standard conditions as shown in Table 1, entry 15. To our delight, the desired 1-phenyl-3-(1phenylpyrrolidin-2-yl)-1H-pyrrole-2,5-dione (5a) was obtained in 75% yield (Table 3).…”
Presented herein is a novel and efficient α-C(sp 3 )− H alkenylation of cyclic amines with maleimides. Mechanistically, this C(sp 3 )−H/C(sp 2 )−H cross dehydrogenative coupling (CDC) reaction involves a cascade procedure including oxidative α-amino radical formation from the cyclic amine substrate and nucleophilic addition of the in situ formed α-amino radical onto the electrondeficient carbon−carbon double bond of maleimide followed by oxidation and β-elimination. Notably, this direct α-functionalization provides an effective alternative to the conventional ionic reaction mode, in which an imine or iminium intermediate is formed to react with electron-rich coupling partners other than electron-deficient ones. In general, this method features readily available and structurally diverse substrates, a green and economical catalyst, a unique reaction pathway, mild reaction conditions, high efficiency, and excellent atom economy. This new reaction enriches the application of Fe(III)-catalyzed C(sp 3 )−H activation and functionalization.
“…After having established an efficient synthesis of αmaleimide substituted cyclic amines with piperidines and morpholines as the substrates, we were then curious about whether this new protocol could be applied for the αfunctionalization of pyrrolidines. 9 Thus, 1-phenylpyrrolidine (4a) was treated with 2a under standard conditions as shown in Table 1, entry 15. To our delight, the desired 1-phenyl-3-(1phenylpyrrolidin-2-yl)-1H-pyrrole-2,5-dione (5a) was obtained in 75% yield (Table 3).…”
Presented herein is a novel and efficient α-C(sp 3 )− H alkenylation of cyclic amines with maleimides. Mechanistically, this C(sp 3 )−H/C(sp 2 )−H cross dehydrogenative coupling (CDC) reaction involves a cascade procedure including oxidative α-amino radical formation from the cyclic amine substrate and nucleophilic addition of the in situ formed α-amino radical onto the electrondeficient carbon−carbon double bond of maleimide followed by oxidation and β-elimination. Notably, this direct α-functionalization provides an effective alternative to the conventional ionic reaction mode, in which an imine or iminium intermediate is formed to react with electron-rich coupling partners other than electron-deficient ones. In general, this method features readily available and structurally diverse substrates, a green and economical catalyst, a unique reaction pathway, mild reaction conditions, high efficiency, and excellent atom economy. This new reaction enriches the application of Fe(III)-catalyzed C(sp 3 )−H activation and functionalization.
“…Furthermore, the usage of a sterically bulky 1‐pyridinyloxazoline Pyox chiral ligand allowed the regio‐ and enantioselective 5‐ exo aminotrifluoromethoxylation of the diphenyl‐substituted substrate (78 %, 97 : 3 ee , CsOCF 3 , THF/CH 2 Cl 2 , −25 °C, 48 h). In their other contribution, a ligand‐controlled regioselective diamination of unactivated alkenes promoted by palladium acetate in the presence of Pyox ligand L 1a and N ‐fluorobenzenesulfonimide (NFSI) was disclosed [18b] . The latter served as oxidant and an electrophilic aminating agent.…”
This review aims to collect and analyze recent results with respect to the use of varied palladium preparations in the synthesis of five-membered nitrogen heterocycles including condensed derivatives. Results have been selected with focus on studies of the last three years. Furthermore, a common feature of all methods treated here is that the nitrogencontaining five-membered ring is formed via ring closing of appropriate starting materials. Selected examples discussed will reveal that a plethora of products from small monocycles to condensed multi-ring systems can be successfully accessed. Major features are wide product ranges, high product yields and stereoselectivities often achieved under mild reaction conditions.
“…Scheme 11 Enantioselective diamination of terminal alkenes with 1azido-1,2-benziodoxol-3(1H)-one Shortly thereafter, the same group reported the cyclization of related sulfonamide tethered terminal alkenes by Pd-catalyzed diamination reactions with NFSI as the nitrogen source and oxidant (Scheme 12). 32 It is noteworthy that the regioselectivity of this process can be modulated through modulation of the ligand architecture. With ligand L7, 6-endo-cyclization is favored, whereas with ligand L8, 5exo-cyclization is favored.…”
Enantioselective diamination of alkenes represents one of the most straightforward methods to access enantioenriched, vicinal diamines, which are not only frequently encountered in biologically active compounds, but also have broad applications in asymmetric synthesis. Although the analogous dihydroxylation of olefins is well-established, the development of enantioselective olefin diamination lags far behind. Nevertheless, several successful methods have been developed that operate by different reaction mechanisms, including a cycloaddition pathway, a two-electron redox pathway, and a radical pathway. This short review summarizes recent advances and identifies limitations, with the aim of inspiring further developments in this area.1 Introduction2 Cycloaddition Pathway3 Two-Electron Redox Pathway3.1 Pd(0)/Pd(II) Diamination3.2 Pd(II)/Pd(IV) Diamination3.3 I(I)/I(III) Diamination3.4 Se(II)/Se(IV) Diamination4 One-Electron Radical Pathway4.1 Cu-Catalyzed Diamination4.2 Fe-Catalyzed Diamination5 Summary and Outlook
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