Range Of Alkenes Research Articles

Visible Light Promoted Site-Specific Functionalization of α-Acyloxy Carboxamides: Unlocking a Forbidden Chemical Space in the Passerini Reaction.

The facile generation of the α-acyloxy carboxamide radical is hereby reported for the first time, utilizing a photoredox catalyzed reaction of Passerini adducts synthesized using a 4-formyl-1,4-dihydropyridine as the carbonyl component. This radical effectively engages in a Giese reaction with a range of olefins, ultimately leading to the synthesis of novel Passerini-derived products not previously amenable to direct aldehyde-based transformations. Consequently, the resulting strategy, developed both in batch and in flow, offers a promising opportunity to expand the chemical space accessible through the Passerini reaction, virtually incorporating "impossible" aldehydes.

Rapid and Modular Access to Multifunctionalized 1,2-Azaborines via Palladium/Norbornene Cooperative Catalysis.

1,2-Azaborines, a unique class of BN-isosteres of benzene, have attracted great interest across several fields. While significant advancements have been made in the postfunctionalization of 1,2-azaborines, challenges still exist for the selective functionalization of the C4 position and access to 1,2-azaborines with five or six independently installed substituents. Here we report a rapid and modular method for C3 and C4 difunctionalization of 1,2-azaborines using the palladium/norbornene (Pd/NBE) cooperative catalysis. Enabled by the C2 amide-substituted NBE, diverse 3-iodo-1,2-azaborines can be used as substrates, showing broad functional group tolerance. Besides ortho arylation, preliminary success of ortho alkylation has also been realized. In addition, a range of alkenes and nucleophiles can be employed for ipso C3 functionalization. The reaction is scalable, and various postfunctionalizations, including forming hexa-substituted 1,2-azaborines, have been achieved.

Photoinduced Vicinal 1,2-Difunctionalization of Olefins for the Synthesis of Alkyl Sulfonamides.

Alkyl sulfonamides are an important class of bioactive molecules. Historical syntheses have relied on multistep sequences incorporating harsh reaction conditions. Photochemical methods have been limited to hydrosulfamoylation, installing only one substituent across an olefin. Herein, radical/polar crossover (RPC) is used to establish the first multicomponent 1,2-difunctionalization reaction incorporating a sulfonamide moiety and a second reaction partner. This protocol, exemplified on a range of olefins, utilizes various commercial sulfamoyl chlorides and organotrifluoroborates as coupling partners.

Dithioallyl cation (3 + 2) cycloadditions under aprotic reaction conditions: rapid access to spiro-fused cyclopentane scaffolds.

We report a general method to effect all-carbon (3 + 2) cycloadditions that can elaborate cyclopentenes from a range of olefins. The required dithioallyl cation reagents can be generated in a newly developed mild protocol starting from 2-allyloxypyridine precursors, thus avoiding the use of strong Brønsted acids. The novel method significantly expands the substrate scope, which now also includes acid-sensitive olefins, and thus enables the preparation of previously inaccessible spiro-fused scaffold types from simple and readily available starting materials.

Palladium-Catalyzed Tandem Carbonylative Diels-Alder Reaction for Construction of Bridged Polycyclic Skeletons.

A palladium-catalyzed tandem carbonylative lactonization and Diels-Alder cycloaddition reaction between aldehyde-tethered benzylhalides and alkenes has been developed. A range of alkenes and aldehyde-tethered benzylhalides bearing different substituents can be successfully transformed into the corresponding bridged polycyclic compounds in good yields. This strategy provides a unique approach to complex lactone-containing bridged polycyclic compounds.

Visible-Light-Enhanced Cobalt-Catalyzed Hydrogenation: Switchable Catalysis Enabled by Divergence between Thermal and Photochemical Pathways

The catalytic hydrogenation activity of the readily prepared, coordinatively saturated cobalt(I) precatalyst, (R,R)-(iPrDuPhos)Co(CO)2H ((R,R)-iPrDuPhos = (+)-1,2-bis[(2R,5R)-2,5-diisopropylphospholano]benzene), is described. While efficient turnover was observed with a range of alkenes upon heating to 100 °C, the catalytic performance of the cobalt catalyst was markedly enhanced upon irradiation with blue light at 35 °C. This improved reactivity enabled hydrogenation of terminal, di-, and trisubstituted alkenes, alkynes, and carbonyl compounds. A combination of deuterium labeling studies, hydrogenation of alkenes containing radical clocks, and experiments probing relative rates supports a hydrogen atom transfer pathway under thermal conditions that is enabled by a relatively weak cobalt–hydrogen bond of 54 kcal/mol. In contrast, data for the photocatalytic reactions support light-induced dissociation of a carbonyl ligand followed by a coordination-insertion sequence where the product is released by combination of a cobalt alkyl intermediate with the starting hydride, (R,R)-(iPrDuPhos)Co(CO)2H. These results demonstrate the versatility of catalysis with Earth-abundant metals as pathways involving open- versus closed-shell intermediates can be switched by the energy source.

ChemInform Abstract: Visible‐Light Promoted Intermolecular Halofunctionalization of Alkenes with N‐Halogen Saccharins.

AbstractThe photoreaction of N‐bromosaccharin with a range of alkenes leads to a mixture of bromoamide (V) and bromoether (VI).

Rhodium(III)-catalyzed internal oxidative coupling of N-hydroxyanilides with alkenes via C–H activation

Described herein is an efficient new method for ortho-olefination of anilides in the presence of AgSbF6 and NaOAc via rhodium(III)-catalyzed internal oxidative C–H bond activation based on hydroxyl as directing and oxidative group. A range of alkenes and functional groups on acetanilides is supported and a possible mechanism is proposed according to the experimental results.

Transition Metal-free Epoxidation of Alkenes Based on the Existence of (2- hydroxypropyl)-β-CD

A green, efficient epoxidation of alkenes with hydrogen peroxide (HO) and sodium bicarbonate (NaHCO3) catalyzed by (2-hydroxypropyl)-β-cyclodextrin (2-hp-β-CD) in aqueous solution has been investigated in detail. A range of alkenes were epoxidized at ambient temperature with high yields.

Matsuda-Heck reaction with arenediazonium tosylates in water.

An environmentally friendly Matsuda–Heck reaction with arenediazonium tosylates has been developed for the first time. A range of alkenes was arylated in good to quantitative yields in water. The reaction is significantly accelerated when carried out under microwave heating. The arylation of haloalkylacrylates with diazonium salts has been implemented for the first time.

Zirconocene-catalyzed sequential ethylcarboxylation of alkenes using ethylmagnesium chloride and carbon dioxide

The zirconocene-catalyzed sequential ethylcarboxylation of alkenes using ethylmagnesium chloride and carbon dioxide has been developed. A range of alkenes were transformed into the corresponding carboxylic acids in high yields.

Selective CH Bond Functionalization of 2‐(2‐Thienyl)pyridine by a Rhodium N‐Heterocyclic Carbene Catalyst

Abstract[Rh(μ‐Cl)(H)2(IPr)]2 (IPr=1,3‐bis‐(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) catalyzes the selective functionalization of 2‐(2‐thienyl)pyridine efficiently with a range of alkenes and internal alkynes. A catalytic cycle is proposed on the basis of the identification of key reaction intermediates and the study of their reactivity by NMR spectroscopy. Theoretical calculations at the DFT level support that the reaction proceeds by initial κ1N coordination of 2‐(2‐thienyl)pyridine followed by the loss of H2 to afford the active catalyst. Subsequently, cyclometalation of 2‐(2‐thienyl)pyridine, coordination of the unsaturated substrate (alkyne or alkene) at the vacant position trans to the hydride, and reductive elimination of the thiophene moiety occur. Finally, cyclometalation of the thiophene moiety renders the hydride cis to the unsaturated substrate, which leads to migratory insertion into the RhH bond and subsequent reductive elimination of the functionalized product.

ChemInform Abstract: Oxidation Cascade with Oxone: Cleavage of Olefins to Carboxylic Acids.

A variety of olefins is shown to be cleaved oxidatively to the corresponding acids with oxone as the reagent. The simple methodology that works well for a range of alkenes, i.e., styrenes, nitrostyrenes, stilbenes, cinnamic acids, chalcones, etc., involves heating of the reactant with oxone in acetonitrile–water mixture (1:1, v/v) at reflux. The oxidation cascade involves initial dihydroxylation followed by oxidative cleavage and oxidation of the resultant aldehydes to acids.

ChemInform Abstract: Rh‐Catalyzed Oxidative C—C Bond Formation and C—N Bond Cleavage: Direct Access to C2‐Olefinated Free (NH)‐Indoles and Pyrroles.

The rhodium-catalyzed oxidative C2-olefination of indoles and pyrroles containing N-arylcarboxamide directing groups with a range of alkenes and subsequent cleavage of directing groups is described. This method provides direct and efficient access to C2-functionalized free (NH)-heterocycles.

Rh-catalyzed oxidative C–C bond formation and C–N bond cleavage: direct access to C2-olefinated free (NH)-indoles and pyrroles

The rhodium-catalyzed oxidative C2-olefination of indoles and pyrroles containing N-arylcarboxamide directing groups with a range of alkenes and subsequent cleavage of directing groups is described. This method provides direct and efficient access to C2-functionalized free (NH)-heterocycles.

Nitrile-Promoted Alkene Epoxidation with Urea–Hydrogen Peroxide (UHP)

An efficient method for alkene epoxidation has been studied systematically using benzonitrile and the complex urea–hydrogen peroxide (UHP), which is an anhydrous form of hydrogen peroxide and has the potential to release hydrogen peroxide in a controlled manner and thus avoid the need to slowly add aqueous H2O2 to the reaction mixture. The absence of water in the reaction media was also beneficial, because it minimized undesired reactions of the oxidized products. A range of alkenes was epoxidized by this method, providing yields ranging from 79% to 96%. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

Ligand-Free Pd-Catalyzed Cross-Coupling Reaction of Olefins and Trialkoxyarylsilanes

A ligand-free Pd-catalyzed method was developed for Heck-type reaction of a wide range of olefins with various trialkoxyarylsilanes. In the presence of Pd(OAc)2, K2CO3, TBAF•3H2O and AgOAc, the cross-coupling products can be ob- tained in moderate to good yields, and the Heck-type reaction displayed high regio- and stereo-selectivities. The mechanism of Heck-type reaction was discussed according to our experimental results and the reported mechanism.

Enantioselective organo-SOMO cycloadditions: a catalytic approach to complex pyrrolidines from olefins and aldehydes.

A new method to rapidly generate pyrrolidines via a SOMO-activated enantioselective (3 + 2) coupling of aldehydes and conjugated olefins has been accomplished. A radical-polar crossover mechanism is proposed wherein olefin addition to a transient enamine radical cation and oxidation of the resulting radical furnish a cationic intermediate which is vulnerable to nucleophilic addition of a tethered amine group. A range of olefins, including styrenes and dienes, are shown to provide stereochemically complex pyrrolidine products with high chemical efficiency and enantiocontrol.

Rare-earth dialkyl and dihydride complexesbearing monoanionic ancillary ligands

This paper gives a brief overview on recent progress in the chemistry of rare-earth dialkyl and dihydride complexes with monoanionic supporting ligands. The dialkyl complexes serve as excellent catalysts for the polymerization and copolymerization of a wide range of olefins to give novel polymer materials difficult to prepare by other means. The dihydride species show unique features in terms of both their structure and reactivity, which are in sharp contrast with those of the monohydride analogues bearing two supporting ligands.

Preparation of 2-azaallyl anions and imines from N-chloroamines and their cycloaddition and allylation

Exposure of N-chloroamines to KO t Bu or LDA, in the presence of PMDETA or HMPA, provides 2-azaallyl anions capable of π4s + π2s cycloaddition reactions with a range of olefins. Good yields were achieved with stabilised systems, however, they were more modest when accessing semi-stabilised 2-azaallyl anions. By modifying the reaction conditions, one-pot dehydrochlorination/allylation can also be achieved with a range of N-chloroamines.