Unactivated Double Bonds Research Articles

Silver-Promoted Radical Cascade Aryldifluoromethylation/Cyclization of 2-Allyloxybenzaldehydes for the Synthesis of 3-Aryldifluoromethyl-Containing Chroman-4-one Derivatives.

A convenient silver-promoted radical cascade aryldifluoromethylation/cyclization of 2-allyloxybenzaldehydes has been developed. Experimental studies disclosed that the addition of aryldifluoromethyl radicals in situ produced from easily accessible gem-difluoroarylacetic acids to unactivated double bonds in 2-allyloxybenzaldehyde was an effective route to access a series of 3-aryldifluoromethyl-containing chroman-4-one derivatives in moderate to good yields under mild reaction conditions.

Cu‐Mediated Synthesis of Indolines and Dihydroisoquinolinones through Arylperfluoroalkylation of Unactivated Alkenes

The copper‐mediated fluroalkylation/cyclization of N‐allyl anilines has been described using fluoroalkyl iodides as fluoroalkylation reagents for the first time. The reaction provides an efficient and direct access to 3‐fluoroalkyl indolines in moderate to good yields with unactivated double bonds as the radical acceptor. This protocol combines a simple experimental procedure with low‐costing fluoroalkylated sources and excellent functional group tolerance.

Synthesis of CF3CH2-Containing Indolines by Transition-Metal-Free Aryltrifluoromethylation of Unactivated Alkenes.

With an unactivated double bond as the radical acceptor, allyl amines underwent a metal-free trifluoromethylation/cyclization cascade with CF3SO2Na (Langlois' reagent), affording CF3CH2-containing indolines and tetrahydroisoquinolines, whose practical syntheses are significant challenges. This protocol features mild conditions, low cost, and a broad substrate scope.

Iron‐Catalyzed exo‐Selective Synthesis of Cyanoalkyl Indolines via Cyanoisopropylarylation of Unactivated Alkenes

AbstractAn iron‐catalyzed cyanoalkylation using azobisisobutyronitrile (AIBN) is reported. With unactivated double bond as the radical acceptor, N‐allyl anilines underwent cyanoisopropylation/cyclization cascade to afford 3‐cyanoalkyl indolines bearing a tertiary nitrile moiety, which were otherwise unavailable. Excellent exo‐selectivity was always observed, and such a selectivity and the unusual performance of the iron catalyst might be related to the metal bridging between the radical and the substrate.magnified image

Silver-Catalyzed Radical Arylphosphorylation of Unactivated Alkenes: Synthesis of 3-Phosphonoalkyl Indolines.

A silver-catalyzed phosphorylation/cyclization cascade of N-allyl anilines was developed, allowing direct access to 3-phosphonoalkyl indolines, which were previously obtainable only via tedious procedures under harsh/toxic conditions. The unactivated double bond serves as the radical acceptor, whereas H-phosphonates or -phosphine oxides act as the radical precursor. This protocol features simple operation, broad substrate scope, and great exo selectivity, and a gram-scale synthesis could be readily carried out.

Selective Halogenation Using an Aniline Catalyst.

Electrophilic halogenation is used to produce a wide variety of halogenated compounds. Previously reported methods have been developed mainly using a reagent-based approach. Unfortunately, a suitable "catalytic" process for halogen transfer reactions has yet to be achieved. In this study, arylamines have been found to generate an N-halo arylamine intermediate, which acts as a highly reactive but selective catalytic electrophilic halogen source. A wide variety of heteroaromatic and aromatic compounds are halogenated using commercially available N-halosuccinimides, for example, NCS, NBS, and NIS, with good to excellent yields and with very high selectivity. In the case of unactivated double bonds, allylic chlorides are obtained under chlorination conditions, whereas bromocyclization occurs for polyolefin. The reactivity of the catalyst can be tuned by varying the electronic properties of the arene moiety of catalyst.

An ELF analysis of the C–C bond formation step in the N-heterocyclic carbene-catalyzed hydroacylation of unactivated C–C double bonds

The changes in electron-density along the C–C bond-formation step in the N-heterocyclic carbene-catalyzed hydroacylation of unactivated double bonds has been studied by an electron localization function (ELF) analysis at the B3LYP/6-31G** level in order to characterize the reaction mechanism. Analysis of DFT reactivity indices and the natural bond orbital and ELF analysis at the most relevant points of the intrinsic reaction coordinate indicate that the reaction path takes place through a two-stage one-step mechanism with non-polar character. In the first stage a hydrogen atom is transferred from the hydroxyl group of Breslow intermediate 12 to the terminal olefinic carbon atom, to yield a pseudodiradical species. The barrierless C–C bond formation in this species constitutes the second stage of the reaction allowing the formation of the corresponding alcohoxy intermediate 13. The present theoretical study establishes that this mechanism is completely different to that involved in the intramolecular Stetter reaction, which is initialized by a polar Michael-type addition.

ChemInform Abstract: Catalytic, Asymmetric, Bromine‐Induced Semipinacol Rearrangements at Unactivated Double Bonds.

AbstractCyclic allylic alcohols rearrange to chiral ketones under optimized conditions.

Catalytic, Asymmetric, Bromine-Induced Semipinacol Rearrangements at Unactivated Double Bonds

A new catalyst system for the enantioselective bromine-induced semipinacol rearrangement of cyclic allylic alcohols is described. Using the commercially available (DHQD)2Pyr catalyst the products containing an all-carbon quaternary chiral centre can be obtained in good yield and high enantioselectivity.

Application of a metathesis reaction in the synthesis of sterically congested medium-sized rings. A direct ring closing versus a double bond migration–ring closing process

An efficient double bond migration-ring closing metathesis reaction leading to cycloheptene derivatives is observed when specific sterically congested 1,9-dienes are treated with the Grubbs' imidazolidene ruthenium catalyst. The simultaneous use of the Grubbs' catalyst and RuClH(CO)(PPh(3))(3) facilitates the tandem bond migration-metathesis process. RuClH(CO)(PPh(3))(3) alone is capable of triggering an unactivated double bond migration that may have preparative applications.

ChemInform Abstract: Study of the Asymmetric Induction of the 1,3-Dipolar Cycloaddition of Chiral Azomethine Ylides with Unactivated Double Bonds.

The asymmetric induction of the 1,3-dipolar cycloaddition reaction between nonstabilized azomethine ylides generated by deprotonation of the corresponding tertiary amine N-oxides (1a-f) with a base and various unactivated olefins (2a-c) or dienes (2d-e) has been studied. The results show that an important induction can be reached with valinol derived N-oxide (1f). The elimination of the chiral substituent in 3-phenyl-N-(1-hydroxymethyl-propyl)-pyrrolidine (8b) allowed to determine the absolute configuration of the major enantiomer (12b) in accordance with the proposed transition state

ChemInform Abstract: N‐Heterocyclic Carbene‐Catalyzed Hydroacylation of Unactivated Double Bonds.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

N-Heterocyclic Carbene-Catalyzed Hydroacylation of Unactivated Double Bonds

An intramolecular N-heterocyclic carbene (NHC)-catalyzed hydroacylation of unactivated double bonds is reported. Systematic variation of the catalyst structure revealed an N-mesitylthiazolylidene annulated with a seven-membered ring to be especially reactive. This NHC enables a unique C-C bond-forming reaction to afford substituted chroman-4-ones in moderate to excellent yields, even ones containing all-carbon quaternary centers.

Cobalt Catalyzed Functionalization of Unactivated Alkenes: Regioselective Reductive C−C Bond Forming Reactions

The cobalt catalyzed hydroaldoximation and hydrocyanooximation of unactivated alkenes is reported. Secondary and tertiary aldoximes and oximonitriles are synthesized with excellent regioselectivity under mild conditions, and conversion of the products to valuable intermediates is documented. The reactions expand the arsenal of reductive carbon-carbon bond forming reactions as well as regioselective functionalizations of unactivated double bonds.

Sequential Organocatalyzed Michael Addition/[3 + 2]-Heterocyclization for the Stereoselective Synthesis of Fused-Isoxazoline Precursors of Enantiopure Cyclopentanoids

We propose an asymmetric synthesis of functionalized cyclopentanoids bearing up to four stereogenic centers from easily accessible nitroalkenes and unsaturated aldehydes. The overall sequence includes an enantioselective organocatalytic Michael addition and a [3 + 2]-heterocyclization between an in situ generated silylnitronate and the unactivated double bond. Finally, the fused isoxazoline can be further transformed to various cyclopentanoids.

Carbometalation of unactivated alkenes by zinc enolate derivatives

The carbometalation reaction of zinc enolates and related stabilised organometallics on unactivated double bonds has emerged over the past decade as a mechanistically interesting and synthetically useful reaction. This Perspective is devoted to these challenging and apparently contra-thermodynamic transformations, with a special focus on recent mechanistic considerations involving radical–polar crossover reaction pathways.

Copolymerization of eight-membered ring-opening allylic sulfide lactone and disulfide monomers with methyl methacrylate and styrene

Apparent reactivity ratios and detailed NMR analysis of copolymerizations of eight membered ring-opening allylic sulfide monomers; 3-methylene-1,5-oxathiocan-2-one 2 and 2,2,4-trimethyl-7-methylene-1,5-dithiocane 5 with methyl methacrylate and styrene are presented. The activated double bond of 2 and unactivated double bond and additional methyl substituents of 5 were found to have a profound affect on reactivity. The copolymerization rates were analyzed based on the lumped parameter k p( f/ k t) 0.5, which was estimated as a function of monomer composition in the feed.

Intramolecular Hydroamination Route to Heterocycles

Intramolecular cyclizative hydroamination of unactivated double and triple bonds under inexpensive zinc-based catalysis is reported. The illustrated catalyst shows excellent solubility in most organic solvents, air and moisture stability, low toxicity and is compatible with a variety of polar functional groups such as ethers, amides and hydroxylamines to give products in excellent, often quantitative yields. Thus, dihydropyridones A and B, dihydropyrrole N-oxides C, tetrahydro-oxazepines D, dihydrooxazines and dihydropyrazines are obtained in excellent conversion. The absence of co-catalyst {[PhNMe2H][B(C6F5)4]} led to the formation of exocyclic double bond isomer A as the major product. On the other hand, the ­dihydropyridone B was observed when an equal amount of the co-catalyst was added. Similarly, the intramolecular hydroamination of non-activated alkenes (e.g., 2-methylpent-4-en-1-amine) was also accomplished.

Unprecedented in situ Oxidative Ring Cleavage of Isoxazolidines: Diastereoselective Transformation of Nitronic Acids and Derivatives into 3‐Hydroxymethyl 4‐Nitro Tetrahydrofurans and Pyrrolidines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Unprecedented in situ oxidative ring cleavage of isoxazolidines: diastereoselective transformation of nitronic acids and derivatives into 3-hydroxymethyl 4-nitro tetrahydrofurans and pyrrolidines.

[reaction: see text] Nitronic acids undergo an intramolecular 1,3-dipolar cycloaddition to unactivated double bonds, and the resulting isoxazolidines spontaneously evolve by an unprecedented in situ oxidative ring cleavage. The extension of this transformation to silyl nitronates results in a general diastereoselective construction of hydroxymethyl nitro functionalized tetrahydro-furans and -pyrrolidine having up to four consecutive stereogenic centers.