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Skeletal reorganization reactions have emerged as an intriguing tool for converting readily available compounds into complicated molecules inaccessible by traditional methods. Herein, we report a unique skeleton‐reorganizing coupling reaction of cycloheptatriene and cycloalkenones with amines. In the presence of Rh/acid catalysis, cycloheptatriene can selectively couple with anilines to deliver fused 1,2‐dihydroquinoline products. Mechanistic studies indicate that the retro‐Mannich type ring‐opening and subsequent intramolecular Povarov reaction account for the ring reorganization. Our mechanistic studies also revealed that skeleton‐reorganizing amination between anilines and cycloalkenones can be achieved with acid. The synthetic utilization of this skeleton‐reorganizing coupling reaction was showcased with a gram‐scale reaction, synthetic derivatizations, and the late‐stage modification of commercial drugs. [ABSTRACT FROM AUTHOR]

New highly functionalized scaffolds, namely 2-(2-furyl)hydroxymethyl-2-cycloalkenones, are reported. The access to these systems is one step using an aqueous Morita–Baylis–Hillman reaction combining hydroxymethylfurfural and glucosyloxymethylfurfural and cycloalkenones for which the reaction conditions (promoter, solvent, concentration, and stoichiometry) have been optimized. • New structures arising from cycloalkenones with hydroxymethylfurfural (HMF) and glucosyloxymethylfurfural (GMF) in Baylis–Hillman reactions. • High-level of functionality in one step. • Contribution to widening the scope of uses of HMF and GMF in fine chemistry. • First use of HMF and GMF in cycloalkenone–Morita-Baylis-Hillman reactions. • One-step, mild and clean conditions. [ABSTRACT FROM AUTHOR]

α,β‐Unsaturated esters and lithium 1,3‐dien‐2‐olates are known to furnish bicyclic lithium enolates by anionic Diels–Alder reactions. However, in principle, the respective products might form not only in a single step but also in two consecutive – or "tandem" – Michael additions, the first of which occurs intermolecularly, the second intramolecularly. Three cyclic lithium dienolates and four esters with a stereogenic Cα=Cβ bond reacted to give Diels–Alder adducts (10 times) or failed to react (2 times). Seven of the reactive combinations furnished adducts wherein the configuration of the former ester moiety had in part inverted. This precludes concerted pathways as their origins. This was a surprise since donors at C‐2 of the 1,3‐diene accelerate normal electron‐demand Diels–Alder reactions in the order alkyl < aryl < alkoxy ≈ trialkylsiloxy < acylamino. With Li⊕O⊖ being a far better donor still, it is not obvious why the mechanism is non‐concerted rather than concerted (and still more asynchronous). Cyclic lithium 1,3‐dien‐2‐olates, like isophorone enolate, and α,β‐unsaturated esters, like methyl acrylate, deliver bicyclic lithium enolates by anionic Diels–Alder reactions. In principle, they may materialize in a single step or by two consecutive Michael additions. Seven anionic Diels–Alder reactions involving esters with a stereogenic Cα=Cβ bond proceeded such that the configuration in the ester moiety was partly inverted. This precludes that these reactions proceed in one step. [ABSTRACT FROM AUTHOR]

Oxidative cleavage of cycloalkenylalkylphosphonates 1 followed by treatment with base gives rise to homologated cycloalkenones 2 in good to excellent yields. Subjecting cycloalk-2-enylphosphonates 3 to identical conditions provides the one-carbon ring-contracted compounds 4 in excellent yields. Oxidative cleavage of γ,δ-unsaturated ketophosphonates 6 followed by treatment with base affords 2-cyclopenten-1-ones 7 in good overall yields. This method may offer a practical alternative to existing methods for effecting one-carbon ring expansion, ring contraction, and annulation reactions. [ABSTRACT FROM AUTHOR]

Aza-Michael addition of 4-aryl-1 H -1,2,3-triazoles to 2-cycloalken-1-ones has been studied in the presence of DABCO as organic base. The reactions were carried out in acetonitrile at room temperature to provide 2,4-disubstituted 2 H -1,2,3-triazoles as major adducts and 1,4-disubstituted 1 H -1,2,3-triazoles as minor adducts. Though the reaction times are longer (4–8 days), the two regioisomers were separated by using column chromatography and the adducts were obtained in very good to excellent combined chemical yields. The electron-rich and electron-poor substituents on aryl moiety of 4-aryl-triazoles could tolerate the reaction conditions to afford the title adducts. [ABSTRACT FROM AUTHOR]

A diepoxide (( E )-1,2-di(7- oxabicyclo [4.1.0]heptan-3-yl)ethane, named DCE), possessing two cyclohexane rings bridged by a double bond was obtained via self-metathesis approach. This unique epoxy structure shows great potential in substantially overcoming the poor performances of plant oil materials in thermal and mechanical aspects. The molecular structure of DCE is more compact and regular than the commercial 3,4-epoxycyclohexylmethyl-3,4- epoxycyclohexanecarboxylate (ECHM) and was evidenced by the small-/wide-angle X-ray scattering. After conetwork was built between epoxidized soybean oil (ESO) and DCE, stiff crosslinks were created through the double bonds of DCE, which restricts the backbone rotation of ESO (P-ESO) networks. DCE-rich domains with dimensions ranging from 0.5 to 2 μm were observed with the increase of DCE, revealed by atomic force microscopy (AFM) phase image and voltage-distance curve. These DCE-rich domains act as micro-scale reinforcements homogenously dispersed in the ESO matrix, effectively sustaining the applied stress and preventing the chain break from high force loading. Compared to P-ESO, the co-polymerized ESO-DCE at 30 wt % DCE loading showed tensile strength of 62 MPa and glass transition temperature of 163 °C that are much higher than 4 MPa and 10 °C for P-ESO, respectively. ECHM also showed significant reinforcement effects on the thermal and mechanical properties of ESO, but DCE's reinforcement effects is doubled compared to ECHM. [ABSTRACT FROM AUTHOR]

Et 3 B/O 2 -mediated radical coupling reactions of O,Te-acetal 2 were explored using diverse electrophilic double bonds. Ethyl radical derived from Et 3 B under air cleaved the C–Te bond of 2 to generate α-alkoxy bridgehead radical I , which reacted with cycloalkenones, cycloalkylidenemalononitriles, allyl halides, and imines at or below ambient temperature. These intermolecular reactions from O,Te-acetal 2 were mild and versatile, and were superior to those of O,Se-acetal 1 in terms of efficiency and substrate scope. A total of 14 new and nine improved coupling reactions are described, all of which realized the installation of the functionalized carbon units at the sterically hindered bridgehead position of trioxaadamantane. [ABSTRACT FROM AUTHOR]

Exocyclic allene natural products and pharmaceutical agents are rare but interesting compounds: Fucoxanthin, grasshopper ketone, and analogues of prostacyclins, cephalosporins, antithrombic agents and sterol biosynthesis inhibitors are representative. Syntheses of exocyclic allenes commonly rely on extended conjugate additions to e.g., alk-2-en-4-ynones, syn S N 2′-like additions to alkynyl oxiranes, and substitution reactions such as electrophilic substitutions of propargylic silanes. We report that the reaction of 3-alkynyl-2-cycloalkenones with 2 equiv of various hydridoaluminates but not hydridoborates proceeds via diastereoselective 1,4-reduction of a vinylogously propargylic intermediate alcoholate to provide exocyclic allenes as major products. Isomeric 3-alkynylcycloalkanols also are observed. [ABSTRACT FROM AUTHOR]

Synthesis of novel C 2 -symmetric 1,2- 1,3- and 1,4- bis-sulfinamides and their use as effective ligands in rhodium (I) catalyzed asymmetric conjugate addition of arylboronic acids to cyclohexenone and cyclopentenones is described. C 2 -symmetry as well as chirality at the sulfur center in the ligand is crucial for the high enantioselectivity in the 1,4-addition reaction. It was also observed that the conjugate addition proceeded with good selectivity with Wilkinson's catalyst as the rhodium source. [ABSTRACT FROM AUTHOR]

Chiral β-aryloxy alcohols are interesting building blocks that form part of drugs like β adrenergic antagonists. Acquiring cyclic rigid analogs to obtain more selective drugs is interesting. Thus, we used whole cells of yeast strains Pichia glucozyma and Candida glabrata to catalyze the reduction of several 2-arenoxycycloalkanones to produce chiral 2-arenoxycycloalcohols with good/excellent enantioselectivity. In both cases, the alcohol configuration that resulted from the carbonyl group reduction was S. Yeast P. glucozyma allowed the conversion of both enantiomers of the starting material to produce 2-arenoxycycloalcohols with configuration (1 S, 2 R) and (1 S, 2 S). The reaction with C. glabrata nearly always allowed the kinetic resolution of the starting ketone, recovering 2-arenoxycycloalkanone with configuration S and (1 S, 2 R)-2-arenoxycycloalcohol. All the four possible stereoisomers of 2-phenoxycyclohexanol and the two enantiomers of 2-phenoxycyclohexanone were obtained by combining the biocatalyzed reaction with the oxidation/reduction of the chiral compounds with standard reagents. This is a simple approach for the synthesis of the rigid chiral moiety 2-arenoxycycloalcohols contained in putative β-blockers 2-arenoxycycloalkanepropanolamines. [ABSTRACT FROM AUTHOR]

C38H58N10O6S4, monoclinic, P21 (no. 4), a = 11.9542(5) Å, b = 11.4057(5) Å, c = 17.2763(8) Å, β = 96.380(1)° V = 2340.97(18) ų, Z = 4, Rgt(F) = 0.0325, wRref(F²) = 0.0836, T = 200 K. [ABSTRACT FROM AUTHOR]

C38H58N10O6S4, monoclinic, P21 (no. 4), a = 11.9542(5) Å, b = 11.4057(5) Å, c = 17.2763(8) Å, β = 96.380(1)° V = 2340.97(18) ų, Z = 4, Rgt(F) = 0.0325, wRref(F²) = 0.0836, T = 200 K. [ABSTRACT FROM AUTHOR]

Wynberg's report from 1977 that natural cinchona alkaloids catalyze the asymmetric conjugate addition of aromatic thiols to cycloalkenones is a landmark discovery in hydrogen bonding organocatalysis. Wynberg proposed that this reaction proceeded via the formation of a thiolate-alkylammonium tight ion pair and activation of the enone electrophile by a hydrogen bond from the catalyst's hydroxyl group. This reaction model provided the mechanistic basis for understanding Wynberg's reaction and many other asymmetric transformations since. Our quantum mechanical calculations reveal a different model should be used to explain the results: the alkylammonium ion activates the enone by Brønsted acid catalysis, and the catalyst's hydroxyl group orients the thiolate nucleophile. The new model rationalizes the stereoselective outcome of Wynberg's reaction and provides a new, general model for asymmetric cinchona organocatalysis. [ABSTRACT FROM AUTHOR]

Two π-conjugated thienylenecycloalkeno[c]pyridine (A–D)2 (cyclopentane, 1, and cycloheptane, 2, units when n = 1 and 3, respectively) compounds were prepared using a palladium C–C coupling reaction. The π–π* absorption peak of compound 1 was observed at the longer wavelength of 392 nm than that of compound 2, which was observed at 364 nm. UV-Vis data reflect the interaction between the thiophene ring (donor – D) and cycloalkeno[c]pyridine (acceptor – A) units. These compounds show photoluminescence (PL) in the range of 466–470 nm and give quantum yields, Φ, of 15%. Furthermore, intermediates 5 and 6 are characterized by their shorter absorption peaks (304 and 292 nm, respectively). The electrochemical parameters of compounds 1 and 2 were characterized using cyclic voltammetry (CV) measurements and theoretical calculations at the DFT/B3LYP/6-311++G(d,p) level. [ABSTRACT FROM AUTHOR]

The combination of 20 mol % of copper iodide and lithium tert-butoxide triggers the formation of a broad range of substituted, functionalized α-alkoxy 2 H-naphthalenones from readily available N-tosylhydrazones. The data suggests that this transformation occurs through cycloaddition of a copper carbenoid with an ester, followed by a Lewis acid-catalyzed [1,2] alkyl shift of the in situ generated alkoxyepoxide intermediate. [ABSTRACT FROM AUTHOR]

The intramolecular Diels-Alder reactions of cycloalkenones and terminal dienes occur with high endo stereoselectivity, both thermally and under Lewis-acidic conditions. Through computations, we show that steric repulsion and tether conformation govern the selectivity of the reaction, and incorporation of either BF, or α-halogenation increases the rate of cycloaddition. With a longer tether, isomerization from a terminal diene to the more stable internal diene results in a more facile cycloaddition. [ABSTRACT FROM AUTHOR]

Enantiomerically pure α -substituted α -aminoortho-sulfinylphenylacetonitriles have been readily prepared by the reaction of diastereoisomeric mixtures of α -amino phenylacetonitriles with differently sized cycloalkenones and 2-methyl cyclopentenone in the presence of lithium bases. The reactions proceeded with high levels of stereoselectivity, generating molecules containing up to three asymmetric carbon centers in just one synthetic step. [ABSTRACT FROM AUTHOR]

This Feature Article describes our mechanistic studies in organocatalytic Rauhut-Currier-type reactions and some applications in target-oriented synthesis. The developed approach involves the cyclization of two tethered Michael acceptors via dienamine intermediates and leads to highly functionalized cycloalkenes. The utility of these intermediates is further demonstrated by the synthesis of biologically important targets, such as optically active iridoid derivatives. 1 Introduction 2 Organocatalytic Cyclization of Tethered α,β-Unsaturated Carbonyl Compounds; Synthesis of Cyclopentene Derivatives 2.1 Mechanistic Proposal 2.1.1 ESI-HRMS Measurements 2.1.2 NMR Experiments 2.1.3 Complementary Reactivity 2.2 Synthetic Applications 3 Organocatalytic Cyclization of Tethered α,β-Unsaturated Carbonyl Compounds; Synthesis of Cyclohexene Derivatives 4 Conclusions [ABSTRACT FROM AUTHOR]

2-Sulfinyl-3-trimethylsilylmethylcycloalkanones unexpectedly undergo γ-sila-Pummerer rearrangement. The first examples of this new type of rearrangement are presented. [ABSTRACT FROM AUTHOR]

The reaction of o-sulfinylbenzyl carbanions with prochiral Michael acceptors, such as differently sized cycloalkenones, proceeded with high levels of stereoselectivity, generating molecules containing up to three asymmetric carbon centers in just one synthetic step. All these reactions involved the use of either a proton or an acylating reagent as the final electrophile. Furthermore, the trapping of the enolate resulting from Michael addition with prochiral electrophiles, such as aldehydes or N-sulfonylimines, allowed the highly stereoselective synthesis of densely functionalized compounds containing four chiral centers in just a one-pot sequence, the stereochemical outcome of the sequence being controlled by the sulfinyl auxiliary. [ABSTRACT FROM AUTHOR]

Halocycloalkenones are demonstrated to function as potent dienophiles in inter- and intramolecular Diels-Alder cycloadditions. We have found 2-brominated cycloalkenone dienophiles to be both highly endo selective and significantly more reactive than their nonhalogenated parent compounds. A method for the facile conversion of brominated cyclobutanone DA adducts to synthetically useful cyclopropyl functional handles is described. [ABSTRACT FROM AUTHOR]

Intramolecular Diels-Alder reactions of cyclobutenone and larger cycloalkenones are described. High levels of endo addition attained from Lewis acid catalysis translate to trans hydrindene junctions upon fragmentation of the tricyclic adducts. [ABSTRACT FROM AUTHOR]

Abstract: Novel carbasugars from Streptomyces lincolnensis have been synthesized from an enantiomerically pure 5-hydroxymethyl-cyclohex-2-enone scaffold via a stereoselective approach. Several structural analogues of those carbasugars have also been synthesized in a stereoselective manner from hydroxymethylated cycloalkenone derivatives. [Copyright &y& Elsevier]

Five- and six-membered α-trimethylsilyl-α,β-unsaturated cycloalkenones were prepared by the Wurtz-Fittig coupling reaction of the corresponding 6-bromo-1,4-dioxaspiro[4,n]cycloalk-6-enes with sodium and chlorotrimethylsilane. Upon treatment with anhydrous AlCl3, the compounds underwent carbon-silicon bond scission to yield a novel class of compounds: the 2-(hydroxydimethylsilyl)cycloalk-2-enones. [ABSTRACT FROM AUTHOR]

The effect on the physicochemical and electrooptical properties of introducing cycloalkanones and cycloalkenones into the molecular structure of liquid crystals is discussed and rationalized in terms of existent theories. [ABSTRACT FROM AUTHOR]

Efficient syntheses of five-, six-, and seven-membered α,β-disubstituted cycloalkenones were achieved. Ring-closing metathesis and allylic oxidative rearrangement were the key steps in this route. To make substituted cycloalkenes from triene substrates constituted of two monosubstituted double bonds and one α,α-disubstituted double bond, ethylene was found to successfully promote equilibria among ring closing-ring opening-ring closing processes. [Copyright &y& Elsevier]

Abstract: The thermal decomposition of 3-(α-trimethylsilyl)alkyl substituted 2-(phenylsulfinyl)cycloalkanones occurs via the γ-sila-Pummerer reaction, affording 3-substituted cycloalk-2-enones and unstable trimethylsilyl benzenesulfenate as an elimination by-product. The starting γ-silyl substituted cycloalkanoyl sulfoxides were obtained through the conjugate addition reaction of nucleophilic reagents to 2-(phenylsulfinyl)cycloalk-2-enones. The tandem conjugate addition/γ-sila-Pummerer reaction investigated here provides a new route to 3-substituted cycloalk-2-enones. [Copyright &y& Elsevier]

The alkylation of dienolates generated from 3-methoxycycloalk-2-enones having a 3'-hydroxyl alkenyl chain provides the corresponding quaternized cycloalkenones in a highly diastereoselective manner. The high degree of stereocontrol in the α-quaternization possibly implies intervention of a rigid chelating transition state that allows an efficient 1,4-asymmetric induction to take place. [ABSTRACT FROM AUTHOR]

A highly selective organocatalytic enantioselective intramolecular Friedel-Crafts type cyclization of cycloalkenone onto a resorcin-type substituent is developed to give a range of spirocyclic indanes. [ABSTRACT FROM AUTHOR]

For the first time, the title reaction is used to transform difluorinated silylenol ethers to difluorinated cycloalkenones under mild conditions. [ABSTRACT FROM AUTHOR]

Review: 85 refs. [ABSTRACT FROM AUTHOR]