Über quantitative Beziehungen Zwischen Fragmenten und Ihren Relativen Intensitäten im Massenspektrometer. III—Messung der Intensitätsverhältnisse aus der α-SWpaltung von Tertiären Alkjoholen und Äthern bei Niedriger Elektronenenergie

The ion intensity ratios from competing α-fissions of 30 tertiary aliphatic alcohols and 24 ethers of tertiary alcohols have been measured at 13 eV. The intensity ratios of ions [M ? alkyl1]+ and [M ? alkyl2]⁺ agree well with the reciprocal mass ratios of the respective ions in the case when the alkyl groups are not methyl (ion mass effect). The intensity ratios of [M ? alkyl]⁺ and [M ? methyl]⁺ are always too high, but intensity ratios of [M ? alkyl1]⁺ and [M ? alkyl2]⁺ may be derived indirectly from them, which also agree well with those values expected from the ion mass effect. By the indirect method it is shown, that for the 2,2-dialkyl-1,3-dioxolanes (ethylene ketals) the ion mass effect plays a dominant role too.     

Dipole moments of some alkyl vinyl and alkyl propenyl ethers

Dipole moments of several alkyl vinyl and alkyl propenyl ethers have been determined by the Halverstadt-Kumler method in benzene solution at 293 K. The μ values depend on the bulkiness of the alkyl group present. In the alkyl vinyl ether series, a part of the varying μ values may be ascribed to changes in molecular geometry with varying bulkiness of the alkyl group. Other factors are clearly involved, since even in the alkyl (Z)-propenyl ether series μ values depend significantly on the alkyl group, although the geometry of the molecules remains essentially constant throughout the series. In the latter series, the total dipole moment is linearly related to the Taft's σ^*-values of the alkyl groups:μ/D=?(1.17±0.15)σ^*+(1.29±0.03). This suggests that the variation of μ with the alkyl radical follows from the changing polar character of the alkyl groups, which leads to changes in the value of the group moment μro.     

Ligand effects on the redox potentials of metal carbonyls : Relationship to co force constants in manganese(I) derivatives

The reversible oxidation potentials E^o of a single series of methylcyclopentadienyldicarbonylmanganese(I) derivatives η⁵-MeCpMn(CO)₂L are measured for a wide variety of ligand types, including L = alkyl and aromatic amines, alkyl cyanide and isocyanide, alkene, alkyl and aryl phosphines and phosphites. The relationship of E^o with the carbonyl force constants evaluated by the Cotton-Kraihanzel method is presented.     

Pd0-Catalyzed Asymmetric Carbonitratation Reaction Featuring an H-Bonding-Driven Alkyl−PdII−ONO2 Reductive Elimination

Reductive elimination of alkyl−Pd^II−O is a synthetically useful yet underdeveloped elementary reaction. Here we report that the combination of an H-bonding donor [PyH][BF₄] and AgNO₃ additive under toluene/H₂O biphasic system can enable such elementary step to form alkyl nitrate. This results in the Pd⁰-catalyzed asymmetric carbonitratations of (Z)-1-iodo-1,6-dienes with (R)-BINAP as the chiral ligand, affording alkyl nitrates up to 96 % ee. Mechanistic studies disclose that the reaction consists of oxidative addition of Pd⁰ catalyst to vinyl iodide, anion ligand exchange between I⁻ and NO₃⁻, alkene insertion and S_N2-type alkyl−Pd^II−ONO₂ reductive elimination. Evidences suggest that H-bonding interaction of PyH⋅⋅⋅ONO₂ can facilitate dissociation of O₂NO⁻ ligand from the alkyl−Pd^II−ONO₂ species, thus enabling the challenging alkyl−Pd^II−ONO₂ reductive elimination to be feasible.     

Direct13C-13C spin-spin coupling constants of olefinic carbons in vinyl ethers

Conclusions In alkyl vinyl ethers, the values of¹J (¹³C=¹³C) SSCC increase with increasing effective volume of the alkyl group, opposite to the change in the corresponding constants in the series of alkyl phenyl ethers.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2249–2252, October, 1982.     

Decarboxylative C(sp3)−O Cross‐Coupling

Alkyl aryl ethers are an important class of compounds in medicinal and agricultural chemistry. Catalytic C(sp³)?O cross‐coupling of alkyl electrophiles with phenols is an unexplored disconnection strategy to the synthesis of alkyl aryl ethers, with the potential to overcome some of the major limitations of existing methods such as C(sp²)?O cross‐coupling and S_N2 reactions. Reported here is a tandem photoredox and copper catalysis to achieve decarboxylative C(sp³)?O coupling of alkyl N‐hydroxyphthalimide (NHPI) esters with phenols under mild reaction conditions. This method was used to synthesize a diverse set of alkyl aryl ethers using readily available alkyl carboxylic acids, including many natural products and drug molecules. Complementarity in scope and functional‐group tolerance to existing methods was demonstrated.     

Site-Selectivity in the Fe+-Mediated C?H/C?C Bond Activation of Aldimines Short Communication

It is demonstrated for the first time that the site-selectivity for the Fe⁺-mediated C? H bond activation of aldimines R¹N?CHR² (R¹, R² = alkyl) involves the alkyl chain R¹ by a factor ≥ 12 in comparison to the alkenyl part R². This finding explains previous observations that dehydrogenation of intermediates formed by alkene loss from either R¹ or R² of R¹N?CHR²/Fe⁺ preferentially involves the alkyl part.     

Nickel-Catalyzed C−I-Selective C(sp2)−C(sp3) Cross-Electrophile Coupling of Bromo(iodo)arenes with Alkyl Bromides

Despite several methodologies established for C(sp²)−I selective C(sp²)−C(sp³) bond formations, achieving arene-flanked quaternary carbons by cross-coupling of tertiary alkyl precursors with bromo(iodo)arenes in a C(sp²)−I selective manner is rare. Here we report a general Ni-catalyzed C(sp²)−I selective cross-electrophile coupling (XEC) reaction, in which, beyond 3° alkyl bromides (for constructing arene-flanked quaternary carbons), 2° and 1° alkyl bromides are also demonstrated to be viable coupling partners. Moreover, this mild XEC displays excellent C(sp²)−I selectivity and functional group compatibility. The practicality of this XEC is demonstrated in simplifying the routes to several medicinally relevant and synthetically challenging compounds. Extensive experiments show that the terpyridine-ligated Ni^I halide can exclusively activate alkyl bromides, forming a Ni^I−alkyl complex through a Zn reduction. Attendant density functional theory (DFT) calculations reveal two different pathways for the oxidative addition of the Ni^I−alkyl complex to the C(sp²)−I bond of bromo(iodo)arenes, explaining both the high C(sp²)−I selectivity and generality of our XEC.     

Study of conjugation effects by NMR spectroscopy. XXIV. Determination of the conformational composition of alkyl phenyl ethers with branched alkyl radicals from the13C-1H and13C-13C spin-spin coupling constants

Conclusions During analysis of the¹³C-¹-H and¹³C-¹³C spin-spin coupling constants of the phenyl group in alkyl phenyl ethers it was established that the steric inhibition of the conjugation due to increase in the branching of the alkyl group partial in nature and is strongest in 2-methyl-2-phenoxypropane, whereas further increase in the effective volume of the alkyl group leads to some decrease in the population of the orthogonal conformer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2463–2467, November, 1985.     

Preparation of N-Alkylphtalimides Assisted by Solid-Liquid Phase-Transfer Systems

N-Alkylphtalimides are intermediates in the synthesis of primary amines¹ and are generally prepared from potassium phtalimide and alkyl halides in anhydrous polar aprotic solvents such as dimethylformamide.² Recently, N-alkylation of potassium phtalimide has been achieved from alkyl halides and methanesulfonates in toluene in the presence of hexadecyltributylphosphonium bromide³.     

Theoretical Study on the Mechanism of Ni‐Catalyzed Alkyl–Alkyl Suzuki Cross‐Coupling

Ni‐catalyzed cross‐coupling of unactivated secondary alkyl halides with alkylboranes provides an efficient way to construct alkyl–alkyl bonds. The mechanism of this reaction with the Ni/ L1 ( L1 =trans‐N,N′‐dimethyl‐1,2‐cyclohexanediamine) system was examined for the first time by using theoretical calculations. The feasible mechanism was found to involve a Ni^I–Ni^III catalytic cycle with three main steps: transmetalation of [Ni^I( L1 )X] (X=Cl, Br) with 9‐borabicyclo[3.3.1]nonane (9‐BBN)R₁ to produce [Ni^I( L1 )(R₁)], oxidative addition of R₂X with [Ni^I( L1 )(R₁)] to produce [Ni^III( L1 )(R₁)(R₂)X] through a radical pathway, and C? C reductive elimination to generate the product and [Ni^I( L1 )X]. The transmetalation step is rate‐determining for both primary and secondary alkyl bromides. KOiBu decreases the activation barrier of the transmetalation step by forming a potassium alkyl boronate salt with alkyl borane. Tertiary alkyl halides are not reactive because the activation barrier of reductive elimination is too high (+34.7 kcal mol^?1). On the other hand, the cross‐coupling of alkyl chlorides can be catalyzed by Ni/ L2 ( L2 =trans‐N,N′‐dimethyl‐1,2‐diphenylethane‐1,2‐diamine) because the activation barrier of transmetalation with L2 is lower than that with L1 . Importantly, the Ni⁰–Ni^II catalytic cycle is not favored in the present systems because reductive elimination from both singlet and triplet [Ni^II( L1 )(R₁)(R₂)] is very difficult.     

Absolute rate constants for the reactions between amino and alkyl radicals at 298 K

The absolute rate constants for the reactions of NH₂ radicals with ethyl, isopropyl, and t-butyl radicals have been measured at 298 K, using a flash photolysis–laser resonance absorption method. Radicals were generated by flashing ammonia in the presence of an olefin. A new measurement of the NH₂ extinction coefficient and oscillator strength at 597.73 nm was performed. The decay curves were simulated by adjusting the rate constants of both the reaction of NH₂ with the alkyl radical and the mutual interactions of alkyl radicals. The results are k(NH₂ + alkyl) = 2.5 (±0.5), 2.0 (±0.4), and 2.5 (±0.5) × 10¹⁰ M^?1·s^?1 for ethyl, isopropyl, and t-butyl radicals, respectively. The best simulations were obtained when taking k(alkyl + alkyl) = 1.2, 0.6, and 0.65 × 10¹⁰M^?1·s^?1 for ethyl, isopropyl, and t-butyl radicals, respectively, in good agreement with literature values.     

侧链含自由基单元的1,4-吡咯并吡咯二酮共轭聚合物的合成和半导体性质研究

合成了两个侧链含有2,2,6,6-四甲基哌啶-1-氧自由基单元(TEMPO)的1,4-吡咯并吡咯二酮(DPP)共轭聚合物PDPP4T-1和PDPP4T-2,并开展了其半导体性质研究。薄膜场效应晶体管器件测试结果显示,相对于不含TEMPO的聚合物PDPP4T,PDPP4T-1和PDPP4T-2的场效应器件性能有所降低,不过,含TEMPO的聚合物器件性能最高仍达到了2.12cm~2·V~(-1)·s~(-1)。进一步通过原子力显微镜和X射线衍射对TEMPO引入后导致性能降低的可能原因进行了研究。     

Cyanogen Bromide Promoted Thiol Dimerization

The synthesis of alkyl thiocyanates by the reaction of thiols with cyanogen chloride has been known,¹ although it is generally supersede by the more convenient displacement of alkyl halides with alkali thio-cyanates.² We wish to describe the behavior of sodium thiolates toward cyanogen bromide.     

Oxidative dealkylation of 4a-alkylated 4a,5-dihydroflavins: Properties of 4a-alkylated flavin radicals

Covalent coenzyme substrate adducts (“σ-complexes”) are probable intermediates in flavin-dependent biological dehydrogenations. As chemical model reaction for the σ-complex decay, oxidative dealkylation of stable 4a-alkyl-4a,5-dihydroflavins was studied as a function of alkyl mobility and nature of the oxidizing agent. The alkyl groups studied were n-propyl, allyl and benzyl, the oxidizing agents ³O₂, ¹O₂^*, nitroxide radical, ferricyanide and light-excited flavin.For all three alkyl residues, the primary reaction is formation of the 4a-alkyl-4a-hydroflavin radical by le^?-abstraction. ³O₂ and ferricyanide are too weak to initiate this step. If, however, the radical 4a-RFl is once formed, at least five decay modes can be observed depending on the nature of R:(1) For saturated R the exclusive decay is back transfer of the electron initially abstracted. In this case, dealkylation can only be obtained with ¹O₂*, albeit with the relatively slow rate of < 10⁶ M^?1s^?1.(2) For unsaturated R further 1e^?-oxidation leads to quantitative formation of oxidized flavin, while the fate of the alkyl group is still uncertain: In any case, ROH and the corresponding aldehydes as well as the dimers R₂ can be excluded as products.(3) Further oxidation by ³O₂ again leads to a quantitative yield of oxidized flavin while the alkyl residues are converted to peroxy radicals. In an autocatalytic reaction they form the corresponding hydroperoxides with starting 4a-R-Fl_redH, leading to acrolein (R = allyl) or benzaldehyde (R = benzyl) as the major products.(4) In the absence of further oxidant, slow intramolecular alkyl migration is observed leading to the stable 5-alkyl-l,5-dihydroflavin isomer.(5) Competitively, alkyl migration occurs intermolecularly with the starting material as carbenium acceptor, resulting in formation of the stable 4a,5-dialkyl-4a,5-dihydroflavin and unsubstituted radical HFl, which disproportionates.     

Relative Stabilities of the Geometrical and Conformational Isomers of 2-Alkylideneoxacycloalkanes. A DFT Study

The relative stabilities of the geometrical and rotational isomers of 2-alkylideneoxacycloalkanes (-oxiranes, -oxetanes, -tetrahydrofurans, and -tetrahydropyrans; alkyl = Et, Pr, i-Bu, 2,2-dimethylpropyl) have been studied by DFT calculations. Independent of the size of the alkyl group, the E and Z isomers of alkylideneoxiranes have almost comparable stabilities (the Z form, however, being slightly favored), but, with increasing size of the heterocyclic ring, the relative stability of the E isomer decreases. This is particularly prominent for the tetrahydropyran derivatives with alkyl = 2,2-dimethylpropyl, in which marked repulsive interactions between the t-Bu group and the 3-CH₂ group of the tetrahydropyran ring make the E form, ca. 13 kJ mol^–1 less stable than the Z isomer. On the other hand, for alkyl = Et, Pr, and i-Bu, the relative stabilities of the geometrical isomers are almost independent of the alkyl group. Besides the relative stabilities of the geometrical isomers, energetics of the rotational isomerism of the alkyl group about the C(sp ³)—C(sp ²) bond is also surveyed.     

Method for Conversion of α-Ketols to Ketones. Deoxygenation with Iodotrimethylsilane

Iodotrimethylsilane has rapidly become a valuable reagent for organic synthesis since its use in the cleavage of alkyl esters and ethers^1,2,3 under essentially neutral conditions was introduced. For example, the conversion of ketals to ketones⁴, alcohols to iodides⁵, alkyl carbamates to amines, and sulfoxides to sulfides⁷ can now be readily promoted by iodotrimethylsilane.     

Characterization of Heterogeneous Interaction Behavior in Ternary Mixtures by a Dielectric Analysis: Equi-Molar H–bonded Binary Polar Mixtures in Aqueous Solutions

The heterogeneous associating behavior of the aqueous binary mixtures of ethyl alcohol, ethylene glycol, glycerol and mono alkyl ethers of ethylene glycol, and aqueous ternary mixtures of equi-molar binary systems (i.e., mono alkyl ethers of ethylene glycol with ethyl alcohol, ethylene glycol and glycerol) have been investigated over the entire concentration range using accurately measured dielectric constants at 25 ^∘C. The concentration dependent values of the excess dielectric parameter ε^E and effective Kirkwood correlation factor g ^eff were determined using the measured values of the static dielectric constant, ε_o, at 1 MHz and the high frequency limiting dielectric constant ε_∞ = n _D ². The observed ε^E values in aqueous binary and ternary mixtures are negative over the entire concentration range, which implies the formation of heterogeneous complexes between these molecules that reduces the effective number of dipoles. The stoichiometric ratio corresponding to the maximum interaction in alcohol + water mixtures increases with an increase in the number of hydroxyl groups of the alcohol molecules, but for mono alkyl ethers of ethylene glycol + water mixtures it decreases with the increase in the molecular size of the mono alkyl ethers. In aqueous ternary mixtures the stoichiometric ratio for the maximum extent of heterogeneous interaction is governed by the molecular size of the mono alkyl ethers. It was also found that the strength of the heterogeneous H–bond connectivities in the water + alcohol systems decrease with an increase in the number of hydroxyl groups of the alcohol molecules. However in the case of water + mono alkyl ether binary mixtures and in ternary mixtures, the strength of H–bond connectivities increases with the increase in the molecular size of the mono alkyl ether. An analysis of the g ^eff values confirms that the heterogeneous interaction involves the orientation of molecular dipoles in the studied systems.     

Electrooxidative Cleavage of Carbon-Carbon Bonds. III. Preparation of Alkanediones from Cycloalkanones Through 2-Phenylthio-1-Cycloalkanols

The tittle electrochemical procedures have been carried out either in a divided cell, giving keto acetals 3 from 2 (R¹ = H, R² = alkyl), or in an undivided cell, affording diketones 4 from 2 (R¹ = R² = alkyl), in moderate to good yields.     

Temperature‐Selective Dual Radical Generation from Alkyl Diiodide: Applications to Synthesis of Asymmetric CABC Multi‐Block Copolymers and Their Unique Assembly Structures

Temperature‐selective radical generation from a newly designed alkyl diiodide (I?R²?R¹?I) was studied. R¹?I and I?R² had different reactivities for generating alkyl radicals in the presence of a tetraoctylammonium iodide (ONI) catalyst. Taking advantage of the temperature selectivity, we used the alkyl diiodide as a dual initiator in ONI‐catalyzed living radical polymerization to uniquely synthesize CABC non‐symmetric multi‐block copolymers. Because of their non‐symmetric structure, CABC multi‐block copolymers form unique assemblies, that is, Janus‐type particles with hetero‐segment coronas and flower‐like particles with hetero‐segment petals.