Formation Of Aziridines Research Articles

Three-membered ring formation catalyzed by α-ketoglutarate-dependent nonheme iron enzymes.

Epoxides, aziridines, and cyclopropanes are found in various medicinal natural products, including polyketides, terpenes, peptides, and alkaloids. Many classes of biosynthetic enzymes are involved in constructing these ring structures during their biosynthesis. This review summarizes our current knowledge regarding how α-ketoglutarate-dependent nonheme iron enzymes catalyze the formation of epoxides, aziridines, and cyclopropanes in nature, with a focus on enzyme mechanisms.

Sc(OTf)3-Catalyzed Domino C-C/C-N Bond Formation of Aziridines with Quinones via Radical Pathway.

Sc(III)-catalyzed domino C-C and C-N bond formation of N-sulfonyl aziridines with quinones has been accomplished to furnish functionalized indolines at a moderate temperature. The umpolung reactivity of aziridines, radical pathway, mild reaction conditions, substrate scope, and coupling of drug molecules in a postsynthetic application are the important practical features.

A Review on Recent Advances in the Synthesis of Aziridines and their Applications in Organic Synthesis

Aziridines are the saturated three-membered cyclic amines that constitute an important group of synthetic intermediates. These could act as a precursor for diverse organic compounds owing to the reactivity due to the ring strain associated with them. The outstanding property of aziridines is their high reactivity towards various nucleophilic and electrophilic reagents to acquire more stable ring-opened or ring-expanded amines that could be obtained from the release of strain energy intrinsic in a small ring. As such, aziridines could be used in the synthesis of 4-7 membered heterocycles of biological and industrial significance, such as azetidines, imidazoles, thiazoles, pyrazines, pyrimidines, benzothiazines, benzodiazepines, etc. Earlier synthesis of aziridines was considered a laborious task due to their instability. However, various synthetic approaches leading to the formation of aziridines are now available in the literature. Recently, green, cost-effective and approaches based on simpler work-up for these reactions have attracted researcher's attention. This review article deals with synthetic routes of aziridines and aziridine applications in organic synthesis.

Development of Molecular Complexity through Nitrene-Transfer Reactions Catalyzed by Copper and Silver Scorpionate Complexes

AbstractFor years, metal–nitrene-transfer reactions have been mainly directed toward C=C bond aziridination or C–H bond amidation reactions. In the last decade, multiple efforts have been made to develop new synthetic approaches to expand the applicability of this powerful tool, resulting in the synthesis of complex structures from relatively simple starting materials. Here, we present our contributions to the area with several novel and, to some degree, unexpected transformations developed by our research group. The catalysts for these nitrene-transfer reactions are copper or silver complexes bearing hydrotrispyrazolyl (scorpionate) ligands. These transformations have contributed to an expansion of the scope of organic compounds accessible by nitrene-transfer reactions and to an understanding of the reactivity of metallonitrene species toward the oxidation of less-explored organic substrates.1 Introduction2 Synthesis of 1,2-Dihydropyridines from Furans3 Regio- and Stereoselective Aziridination of Dienes4 Chemoselective Synthesis of Aminimides from Amines5 Synthesis of Sulfinamides and Isothiazoles from Alkynes6 Formation of Azetidines and Methylene Aziridines from Allenes7 Conclusion

Stereospecific Al‐Catalysed TandemC−N/C−SeBond Formation of Isoselenocyanates with Aziridines: Synthesis and DFT Study

AbstractAl‐catalyzed stereospecific tandemC−N/C−Sebond formation of chiral aziridines with isoselenocyanates is described with 90–99% ee and 77–91% yields. The mechanistic investigation using the computational study suggests that the reaction involves a concerted pathway (SN2). The selectivity and substrate scope are the important practical features.magnified image

ChemInform Abstract: Oxidative Aminoaziridination of 2‐Vinylfuran Derivatives as an Approach to Hexa‐2,5‐diene‐1,4‐dione Monohydrazones.

AbstractOxidative addition of N‐aminophthalimides to 2‐vinylfuran derivatives gives the title compounds instead of 2‐furylaziridines.

Efficient Trapping of 1,2-Cyclohexadienes with 1,3-Dipoles.

1,2-Cyclohexadienes are transient intermediates that undergo rapid dimerization and intermolecular trapping with activated olefins and heteroatomic nucleophiles. Fluoride-mediated desilylative elimination of readily accessible 6-silylcyclohexene-1-triflates allows the mild, chemoselective, and functional-group tolerant generation of cyclic allene intermediates, which undergo efficient trapping reactions with stable 1,3-dipoles. The reactions proceed with high levels of both regio- and diastereoselectivity. The reaction of cyclic allenes with azides is accompanied by the facile loss of dinitrogen, resulting in the formation of tetrahydroindoles or polycylic aziridines depending on the azide employed.

An Efficient Aziridination of Styrenes Promoted by Visible Light

Styrenes reacted with sulfonamide in the presence of potassium carbonate and iodine in CHCl3 under visible light irradiation to produce the corresponding aziridines in moderate to good yields. A reaction mechanism to explain the formation of aziridines is also proposed.

Highly Strained Heterocycles Constructed from Boron-Boron Multiple Bonds and Heavy Chalcogens.

The reactions of a diborene with elemental selenium or tellurium are shown to afford a diboraselenirane or diboratellurirane, respectively. These reactions are reminiscent of the sequestration of subvalent oxygen and nitrogen in the formation of oxiranes and aziridines; however, such reactivity is not known between alkenes and the heavy chalcogens. Although carbon is too electronegative to affect the reduction of elements with lower relative electronegativity, the highly reducing nature of the B-B double bond enables reactions with Se(0) and Te(0) . The capacity of multiple bonds between boron atoms to donate electron density is highlighted in reactions where diborynes behave as nucleophiles, attacking one of the two Te atoms of diaryltellurides, forming salts consisting of diboratellurenium cations and aryltelluride anions.

Oxidative Aminoaziridination of 2‐Vinylfuran Derivatives as an Approach to Hexa‐2,5‐diene‐1,4‐dione Monohydrazones

AbstractThe oxidative addition of N‐aminophthalimide to substituted 2‐vinylfurans provides monophthaloylhydrazones of (2Z)‐hexa‐2,5‐diene‐1,4‐dione derivatives instead of 2‐furylaziridines by proceeding through an aziridination of the endocyclic furan C=C bond followed by a regio‐ and stereoselective rearrangement of the bicyclic intermediate. The formation of stable aziridines can then occur through the aziridination of the (E)‐C=C bond of these phthaloylhydrazones. Detailed structure elucidations and mechanistic considerations are provided.

ChemInform Abstract: Diastereoselective Formation of Aziridines from Diazocarbonyl Compounds and N‐(O‐Pivaloylated D‐Galactosyl)benzylideneamines and Ring‐Opening Reactions with P‐Toluenethiol.

N-Galactosyl aziridines were synthesized via BF3·OEt2 promoted addition of carbenes generated from diazocarbonyl compounds with O-pivaloylated β-D-galactosylimines in good yields and high diastereoselectivity. The ring-opening reactions with p-toluenethiol of the aziridines provided enantiometrically pure β-S-substituted phenylalanine derivatives in a highly regioselective manner.

Diastereoselective formation of aziridines from diazocarbonyl compounds and N-(O-pivaloylated D-galactosyl)benzylideneamines and ring-opening reactions with p-toluenethiol.

N-Galactosyl aziridines were synthesized via BF3·OEt2 promoted addition of carbenes generated from diazocarbonyl compounds with O-pivaloylated β-D-galactosylimines in good yields and high diastereoselectivity. The ring-opening reactions with p-toluenethiol of the aziridines provided enantiometrically pure β-S-substituted phenylalanine derivatives in a highly regioselective manner.

Direct Catalytic Asymmetric Mannich-Type Reaction of α-Sulfanyl Lactones

Catalytic asymmetric Mannich-type reactions of α-sulfanyl lactones to aldimines were promoted by a chiral Ag complex/DBU binary catalyst. The reaction proceeded in a syn-selective manner in high enantioselectivity. Alkylative activation of the sulfide of the Mannich adduct allowed for the formation of trisubstituted aziridines.

Photoinduced and Thermal Denitrogenation of Bulky Triazoline Crystals: Insights into Solid-to-Solid Transformation

The photoinduced and thermal denitrogenation of crystalline triazolines with bulky substituents leads to the quantitative formation of aziridines in clean solid-to-solid reactions despite very large structural changes in the transition from reactant to product. Analysis of the reaction progress by powder X-ray diffraction, solid-state (13)C CPMAS NMR, solid-state FTIR spectroscopy, and thermal analysis has revealed that solid-to-solid reactions proceed either through metastable phases susceptible to amorphization or by mechanisms that involve a reconstructive phase transition that culminates in the formation of the stable phase of the product. While the key for a solid-to-solid transformation is that the reaction occurs below the eutectic temperature of the reactant and product two-component system, experimental evidence suggests that those reactions will undergo a reconstructive phase transition when they take place above the glass transition temperature.

ChemInform Abstract: Atom‐Economical C2 + N1 Aziridination: Progress Towards Catalytic Intermolecular Reactions Using Alkenes and Aryl Azides

AbstractReview: ca. 50 refs.

Atom-Economical C2 + N1 Aziridination: Progress towards Catalytic Intermolecular Reactions Using Alkenes and Aryl Azides

The direct synthesis of aziridines from alkenes and a nitrene source with the correct functionality on the nitrogen atom has remained an elusive goal in synthetic chemistry. Ruthenium, cobalt, and iron porphyrin complexes have been demonstrated to catalyze the formation of aziridines from electron-withdrawing aryl azides and a limited selection of conjugated alkenes. Our group is expanding the scope of catalytic aziridination to include electron-donating aryl azides and aliphatic alkenes through the use of a novel tetracarbene iron catalyst.

ChemInform Abstract: Aziridines in One Step From Hydantoins via Red‐Al Mediated Ring‐Contraction.

AbstractThe use of excess Red‐Al, elevated temperatures and long reaction times favor the formation of aziridines over imidazolidinones.

Aziridines from Intramolecular Alkene Aziridination of Sulfamates: Reactivity toward Carbon Nucleophiles. Application to the Synthesis of Spisulosine and Its Fluoro Analogue

Catalytic intramolecular alkene aziridination of sulfamate is an emerging methodology for the asymmetric synthesis of chiral functionalized amines involving the formation of bicyclic aziridines. This study demonstrates the ability of the latter to undergo ring-opening with various carbon nucleophiles: Grignard reagents, lithium salts of terminal alkynes, dithiane, malonate. These S(N)2-type reactions occur with high levels of regio- and chemoselectivity to generally afford seven-membered cyclic sulfamidates in good yields. Carbon nucleophiles have also been found to react with these sulfamidates provided that the sulfamate ester has been previously activated by introduction of a tosyl substituent on the NH group. The versatility of this strategy has been illustrated with the syntheses of spisulosine and its fluoro analogue.

Catalytic Asymmetric Aziridination of α,β‐Unsaturated Aldehydes

The development, scope, and application of the highly enantioselective organocatalytic aziridination of α,β-unsaturated aldehydes is presented. The aminocatalytic azirdination of α,β-unsaturated aldehydes enables the asymmetric formation of β-formyl aziridines with up to >19:1 d.r. and 99% ee. The aminocatalytic aziridination of α-monosubstituted enals gives access to terminal α-substituted-α-formyl aziridines in high yields and up to 99% ee. In the case of the organocatalytic aziridination of disubstituted α,β-unsaturated aldehydes, the transformations were highly diastereo- and enantioselective and give nearly enantiomerically pure β-formyl-functionalized aziridine products (99% ee). A highly enantioselective one-pot cascade sequence based on the combination of asymmetric amine and N-heterocyclic carbene catalysis (AHCC) is also disclosed. This one-pot three-component co-catalytic transformation between α,β-unsaturated aldehydes, hydroxylamine derivatives, and alcohols gives the corresponding N-tert-butoxycarbonyl and N-carbobenzyloxy-protected β-amino acid esters with ee values ranging from 92-99%. The mechanisms and stereochemistry of all these catalytic transformations are also discussed.

Addition of N-Heterocyclic Carbenes to a Ruthenium(VI) Nitrido Polyoxometalate: a New Route to Cyclic Guanidines

The scope of N-atom transfer from the electrophilic ruthenium(VI) nitrido containing polyoxometalate [PW(11)O(39)Ru(VI)N](4-) has been extended to the N-heterocyclic carbene {CH(2)(Mes)N}(2)C and the coupling product {CH(2)(Mes)N}(2)CNH(2)(+) characterized by (1)H NMR and high-resolution mass spectrometry. Because guanidines display many fields of applications ranging from biology to supramolecular chemistry, this could afford an original route to the synthesis of cyclic guanidines. This also enlarges the potential of nitrido complexes in the synthesis of heterocycles, mainly illustrated in the literature through the formation of aziridines through N-atom transfer to alkenes. In the course of the reaction, the ruthenium(III)-containing polyoxometallic intermediate [PW(11)O(39)Ru(III){NC{N(Mes)CH(2)}(2)}](5-) has been thoroughly characterized by continuous-wave and pulsed electron paramagnetic resonance, which nicely confirms the presence of the organic moiety on the polyoxometallic framework, Ru K-edge X-ray absorption near-edge structure, and electrochemistry.