[1+1+1] Cyclotrimerization for the Synthesis of Cyclopropanes

The synthesis of small rings by functionalization of C(sp³)?H bonds remains a great challenge. We report for the first time a copper‐catalyzed [1+1+1] cyclotrimerization of acetophenone derivatives under mild reaction conditions. The reaction has a broad scope for the stereoselective synthesis of cyclopropanes by trimerization of acetophenone. The developed transformation is based on an extraordinary copper‐catalyzed cascade process that allows saturated carbocycles to be obtained for the first time by cyclotrimerization through functionalization of C(sp³)?H bonds. The cascade of sixfold C(sp³)?H bond functionalization allows the synthesis of cyclopropanes in a highly stereoselective approach.     

Viscosity of the systems m-xylene, +1-propanol, +2-propanol, +1-butanol, +t-butanol

Viscosities, η, of the systems, m-xylene, +1-propanol, +2-propanol, +1-butanol and +t-butanol have been measured for the whole range of composition at 303.15, 308.15, 313.15, 318.15 and 323.15?K. The variation of viscosities has been plotted against mole fraction of alkanols. Viscosities have been found to increase slowly up to a considerable concentration of alkanols, followed by a rapid rise of viscosities at higher concentrations. The slow rise of viscosity is attributed to dissociation of alkanols in m-xylene, while the rapid rise of viscosity is ascribed to self-association of alkanols. Excess viscosities, η^E, have been plotted as a function of mole fraction of alkanols. The curves show negative values for the whole range of composition, with minima occurring in alkanol-rich region.?η?and η^E have been fitted to appropriate polynomial equations. The study shows the effect of branching and chain length of alkanols on?η?and η^E.     

[2+2+1+1] Cycloaddition for de novo Synthesis of Densely Functionalized Phenols

A unique benzannulation strategy for regioselective de novo synthesis of densely functionalized phenols is described. Through metal-mediated formal [2+2+1+1] cycloaddition of two different alkynes and two molecules of CO, a series of densely functionalized phenols were obtained. The benzannulation strategy allows efficient regioselective installation up to five different substituents on a phenol ring. The resulting phenols have a substitution pattern different from those obtained from Dötz and Danheiser benzannulations.     

A multicomponent formal [1+2+1+2]-cycloaddition for the synthesis of dihydropyridines

Reaction of methoxyvinylmethylketone with different amines and aldehydes under Lewis-acid catalysed conditions results in a novel, formal, step-wise [1+2+1+2]-cycloaddition to give dihydropyridine products.     

Efficient [4+1]/[3+2+1] bis-cyclizations stereoselectively yielding unprecedented polyacyclic indeno-fused xanthenes

Concise and efficient [4+1]/[3+2+1] bis-cyclizations of o-phthalaldehyde with cyclic 1,3-dicarbonyls have been established for the stereoselective synthesis of unprecedented polycyclic indeno[2,1-l]xanthene derivatives. The multicomponent domino reaction (MDR, AB₂ type) is easy to perform by mixing inexpensive substrates in HOAc at room temperature. The present synthesis shows attractive properties such as the simple one-pot fashion, high bond-forming efficiency, and easy purifications. Up to two new rings and four sigma-bonds were achieved in these MDRs without using any metal catalysts.     

Rhodium-catalyzed [2+2+1+1] cyclocarbonylative coupling of alkynes with carbon monoxide affording tetrasubstituted p-benzoquinones

In this strategy, the tetrasubstituted benzoquinones have been prepared directly by a [2+2+1+1] cyclocarbonylative coupling reaction of internal alkynes with CO in the presence of [RhCl(CO)2]2. The low concentration of CO in the reaction is the crucial point for the chemoselective formation of tetrasubstituted benzoquinones in good to high yields. Functional groups such as chloro, methoxy, cyano, vinyl, fluoro, and carboxylate are tolerated under the reaction conditions.     

Selective [2+1+1] Fragmentation of P4 by heteroleptic Metallasilylenes

Small-molecule activation by low-valent main-group element compounds is of general interest. We here report the synthesis and characterization (¹H, ¹³C, ²⁹Si NMR, IR, sc-XRD) of heteroleptic metallasilylenes L¹(Cl)MSiL² (M=Al 1 , Ga 2 , L¹=HC[C(Me)NDipp]₂, Dipp=2,6-ⁱPr₂C₆H₃; L²=PhC(N^tBu)₂). Their electronic nature was analyzed by quantum chemical computations, while their promising potential in small-molecule activation was demonstrated in reactions with P₄, which occurred with unprecedented [2+1+1] fragmentation of the P₄ tetrahedron and formation of L¹(Cl)MPSi(L²)PPSi(L²)PM(Cl)L¹ (M=Al 3 , Ga 4 ).     

The Lewis acid-catalyzed [3+1+1] cycloaddition of azomethine ylides with isocyanides

A Lewis acid-catalyzed [3+1+1] cycloaddition reaction between aliphatic isocyanides and azomethine ylides generated in situ from aziridines, leading to pyrrolidine derivatives, has been developed. This reaction proceeds smoothly under mild conditions and can also be modified by employing aromatic isocyanides to generate four-membered heterocycles, azetidines, through a [3+1] cycloaddition reaction.     

Spin-forbidden c 3Sigma1+<--X 1Sigma+ band system of YF

Optical spectra of jet-cooled diatomic YF have been recorded using resonant two-photon ionization spectroscopy. A vibrational progression corresponding to the c 3Sigma1+<--X 1Sigma+ system has been identified. The vibrational frequency omegae' and anharmonicity omegae'xe' of the c 3Sigma+ state are 546.70 and 2.45 cm-1, respectively. The 0-0, 1-0, and 2-0 bands of the c 3Sigma1+<--X 1Sigma+ system were rotationally resolved and analyzed, allowing the v'=0, 1, and 2 levels of the c 3Sigma1+ substate to be characterized. From these studies, Be'=0.269 81(3) cm-1, alphae'=0.001 72(3) cm-1, and re'=1.9979(1) A were obtained (1sigma error limits). For these levels the spin-spin coupling constant lambdav is identical within experimental error, as lambda=-22.5 cm-1. The spin-forbidden c 3Sigma1+<--X 1Sigma+ transition is made allowed by spin-orbit interaction between the c 3Sigma1+ and the B 1Pi states. Excited state lifetimes of the c 3Sigma1+ and the B 1Pi states have been measured as 7.11(41) and 0.133(15) micros, respectively. A spin-orbit analysis shows that the c 3Sigma1+ state is contaminated with 2% B 1Pi character, which is approximately sufficient to explain the 7 micros lifetime of the c 3Sigma1+ state.     

Synthesis of 1,2,3-triarylpyrroles from 1-benzylbenzotriazoles via [1 + 2 + 2] annulation

1,2,3-Triarylpyrroles 7 have been synthesized by sequential lithiation and alkylation of 1-benzylbenzo-triazoles 1 with 2-bromoacetaldehyde diethyl acetal (2) and N-benzylideneaniline (4), followed by treatment with formic acid in ethanol.     

Multicomponent cycloadditions: the four-component [5+1+2+1] cycloaddition of vinylcyclopropanes, alkynes, and CO

Prompted by the view that intermediates of transition metal-catalyzed reactions could be intercepted by one or more additional components, studies in our laboratory have led to the design and development of new three-component [5+2+1], [4+2+1], and [2+2+1] cycloadditions. These continuing studies have now led to the identification of a fundamentally new four-component [5+1+2+1] cycloaddition reaction of vinylcyclopropanes, alkynes and CO, yielding hydroxyindanone products in generally good yields. Terminal alkynes bearing aryl or alkyl groups are tolerated well. Substitution at any position of the VCP leads predictably to substituted hydroxyindanone products. Using a bis-alkynyl substrate, the reaction can be carried out bi-directionally, forming 10 C-C bonds and four new rings from seven components in a single, operationally simple process.     

Synthesis of symmetric macrocyclic diesterdihyrazides using successive [2+1]- and [1+1]-condensations

Potentially useful symmetric macrocyclic diesterdihydrazides were synthesized efficiently from available petrochemical products (tetrahydropyran and 4-methyltetrahydropyran) using successive [2+1]-condensation of 8-hydroxyoctan-2-one and its 6-methyl derivative with glutaric and adipic chlorides and [1+1]-condensation of the intermediate diketodiesters with glutaric dihydrazide.     

Excess Molar Volume of 1-propanol+Aniline, +N-methylaniline, +N,N-dimethylaniline

Abstract

Densities of the systems, 1-Propanol(P)+aniline(A), 1-Propanol(P)+N-Methylaniline (NMA) and 1-Propanol(P)+N,N-Dimethylaniline(DMA) have been measured from 21°C to 50°C at an interval of 5°C. The excess molar volumes, V ^E, of the systems, P+A and P +NMA have been found to be negative for the whole range of composition. V^E of the system P+DMA has also been found to be negative, except in DMA-rich region where small positive excess volume is observed. The negative excess volume has been explained primarily in terms of strong specific interaction and size difference of unlike molecules. The magnitude of the negative excess volumes of these systems is of the order, P+A > P + NMA > P + DMA, which has been strongly influenced by steric effect due to CH₃ group attached to N-atom of NMA and DMA. In the highly rich region of DMA in P+DMA system the small positive excess volume is accounted for by the steric effect and breaking up of H-bond of 1-Propanol.     

Three-Pronged Attack by Homologous Far-red/NIR AIEgens to Achieve 1+1+1>3 Synergistic Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) has long been shown to be a powerful therapeutic modality for cancer. However, PDT is undiversified and has become stereotyped in recent years. Exploration of distinctive PDT methods is thus highly in demand but remains a severe challenge. Herein, an unprecedented 1+1+1>3 synergistic strategy is proposed and validated for the first time. Three homologous luminogens with aggregation-induced emission (AIE) characteristics were rationally designed based on a simple backbone. Through slight structural tuning, these far-red/near-infrared AIE luminogens are capable of specifically anchoring to mitochondria, cell membrane, and lysosome, and effectively generating reactive oxygen species (ROS). Notably, biological studies demonstrated combined usage of three AIE photosensitizers gives multiple ROS sources simultaneously derived from several organelles, which gives superior therapeutic effect than that from a single organelle at the same photosensitizers concentration. This strategy is conceptually and operationally simple, providing an innovative approach and renewed awareness of improving therapeutic effect through three-pronged PDT.     

Nickel-catalyzed [3+1+1] cycloaddition reactions of alkenyl Fischer carbene complexes with methylenecyclopropanes

Methylenecyclopentanones were synthesized by the nickel-catalyzed [3+1+1] cycloaddition reactions of alkenyl Fischer carbene complexes with methylenecyclopropanes. The methylenecyclopropane was transformed into the C(2)-symmetric bis-cyclopentapyridazine derivative by reacting with p-toluenesulfonyl hydrazine.     

Thermodynamic properties of the ternary system MTBE+1-propanol+hexane

Experimental excess molar enthalpies and excess molar volumes of the ternary system x₁MTBE+x₂1-propanol+(1-x₁-x₂) hexane and the involved binary mixtures have been determined at 298.15 K and atmospheric pressure. Excess molar enthalpies were measured using a standard Calvet microcalorimeter, and excess molar volumes were determined from the densities of the pure liquids and mixtures, using a DMA 4500 Anton Paar densimeter. The UNIFAC group contribution model (in the versions of Larsen et al., and Gmehling et al.) has been employed to estimate excess enthalpies values. Several empirical expressions for estimating ternary properties from experimental binary results were applied.     

An efficient three-component reaction involving [3 + 1 + 1] furannulation leading to furanonaphthoquinones in water

An efficient and clean green synthesis of highly substituted linear naphtho[2,3-b]-furan-4,9-dione derivatives, starting from 2-hydroxy-1,4-naphthoquinone, alkyl isocyanides and a variety of aldehydes, is described. This new method provides the first example of an efficient regioselective synthetic method for the synthesis of linear naphtho[2,3-b]-furan-4,9-dione ring systems by formation of three bonds. This [3 + 1 + 1] furannulation strategy affords furanonaphthoquinones in moderate to high yields, using water as a cheap, non-toxic, environmentally friendly solvent, in a one-step reaction, without the need of complicated work-up procedures. Correspondence: Mohammad Bagher Teimouri, Petrochemical Department, Iran Polymer and Petrochemical Institute, P.O. Box 14965-115, Tehran, Iran.     

Photolysis of alkyl iodides at 147.0 nm. The reaction H + CnH2n + 1I → HI + CnH2n + 1

The 147 nm (8.4 eV) photolysis of gaseous C₂H₅I, n-C₃H₇I, and sec-C₃H₇I was investigated in the presence of and absence of HI. The main overall processes are: These dissociative processes occur mainly as a result of initial cleavage of the weak C? I bond, followed by decomposition of the internally excited alkyl radicals. In all cases, approximately 5-10% of the alkyl radicals thus formed do not undergo dissociation at pressures around 3-7 torr. There is also evidence for the elimination of HI as well as C? C cleavage in the primary dissociation. The former is indicated by deuterium labeling experiments and the formation of cyclopropane (Φ = 0.04) as a product in the photolysis of n-C₃H₇I. Because the processes listed above provide a constant source of H atoms whose quantum yield can be exactly determined, it was feasible to obtain accurate values for k_a/k_b: For thermally equilibrated H atoms (300 K), k_a/k_b is 0.44 ± 0.04, 0.57 ± 0.06, 0.95 ± 0.1, and 0.024 ± 0.01 for C₂H₅I, n-C₃H₇I, sec-C₃H₇I, and C₂H₅Br, respectively.