三甲基溴代硅烷促进的非环状与环状缩醛(酮)的合成

以三甲基溴代硅烷作为反应促进剂, 在室温和原甲酸酯或原乙酸酯存在的条件下, 利用醇、二醇处理羰基化合物, 高收率地实现了一系列非环状与环状缩醛(酮)的合成. 产物结构经1H NMR、元素分析等进行了表征.     

A Facile Route to Cyclic and Acyclic Alkyl-Arginines

Treatment of commercially available alkyl and cycloalkyl thioureas with methyl iodide provides the corresponding S-alkylisothiouronium iodide which reacts directly with ornithine to yield the title compounds.     

Sm-Catalyzed Synthesis and Biological Activity of Acyclic and Cyclic Azadiperoxides

Russian Journal of Organic Chemistry - Acyclic diaminodiperoxides and cyclic azadiperoxides are synthesized by the reaction of 1,1-bis-(hydroperoxy)cycloalkanes with formaldehyde and primary...     

Forming Stereogenic Centers in Acyclic Systems from Alkynes

The combined carbometalation/zinc homologation followed by reactions with α‐heterosubstituted aldehydes and imines proceed through a chair‐like transition structure with the substituent of the incoming aldehyde residue preferentially occupying a pseudo‐axial position to avoid the two gauche interactions. The heteroatom in the axial position produces a chelated intermediate (and not a Cornforth–Evans transition structure for α‐chloro aldehydes and imines) leading to a face differentiation in the allylation reaction. This method provides access to functionalized products in which three new carbon–carbon bonds and two to three stereogenic centers, including a quaternary one, were created in acyclic systems in a single‐pot operation from simple alkynes.     

Synthesis of Cyclic and Acyclic ortho-Aryloxy Diaryliodonium Salts for Chemoselective Functionalizations

Two regioselective, high-yielding one-pot routes to oxygen-bridged cyclic diaryliodonium salts and ortho-aryloxy-substituted acyclic diaryliodonium salts are presented. Starting from easily available ortho-iodo diaryl ethers, complete selectivity in formation of either the cyclic or acyclic product could be achieved by varying the reaction conditions. The complimentary reactivities of these novel ortho-oxygenated iodonium salts were demonstrated through a series of chemoselective arylations under metal-catalyzed and metal-free conditions, to deliver a range of novel, ortho-functionalized diaryl ether derivatives.     

Studies on the Imide-Amide Rearrangement of Cyclic Phosphorimidates

Abstract

The imide-amide rearrangement of cyclic phosphorirnidates 1 leads to the formation of phosphoramidates 3, either thermally (> 180°C) or by the action of a Lewis acid (BF₃ OEt₂, 60°C)¹. In an attempt to develop a synthetic pathway to β aminoalcohols based on this rearrangement, we have thoroughly studied the influence of the structure of the reactants on the Lewis acid catalysed rearrangement. This study brought some insight into the mechanism of this particular reaction, namely the identification of a new polymeric structure 2. not yet described, which is converted into 3 by thermolysis². The formation of 2 at rt was followed by ³ P NMR. In the case of R′? Ph, the reactivity observed for R₂N was: i-Pr₂N > Pyrrolidine > n-Bu²N For R²=i-Pr₂, the observed R′ group effect was: Bn > 4-NO₂Bn > Ph. No reaction was observed for R′ ? Ts, n-Oct. In the case of the groups R′ ? Bn and R₂=i Pr₂ the Lewis acid effect was also studied: BF₃OEt₂, BF₃MeOr-Bu, Sc(OTf)₃ or CITi(Oi-Pr)₃ or Me₂SnCl₂.     

Unsymmetrical,Cyclic Diborenes and Thermal Rearrangement to a Borylborylene

Cyclic diboranes(4) based on a chelating monoanionic benzylphosphine linker were prepared through boron–silicon exchange between arylsilanes and B₂Br₄. Coordination of Lewis bases to the remaining sp² boron atom yielded unsymmetrical sp³‐sp³ diboranes, which were reduced with KC₈ to their corresponding trans‐diborenes. These compounds were studied with a combination of spectroscopic methods, X‐ray diffraction, and DFT calculations. PMe₃‐stabilized diborene 6 was found to undergo thermal rearrangement to gem‐diborene 8 . DFT calculations on 8 reveal a polar boron–boron bond, and indicate that the compound is best described as a borylborylene.     

Stereocontrolled Construction of Complex Cyclic Ketones via Oxy-Cope Rearrangement

Convergency is a highly serviceable aspect of organic synthesis, particularly when its application is accompanied by high levels of chirality transfer and regiocontrol. A reaction that is notably well suited to these objectives is the oxy-Cope rearrangement. In addition, the benefits that can accrue from suitable condensation of β γ-unsaturated ketones with a vinyl organometallic and subsequent [3,3] sigmatropic shift are substantive enhancement in structural complexity and the ability to generate a myriad of polycyclic frameworks. Another profitable feature is the complementary regeneration of the carbonyl group in a new structural context. In view of the pivotal role played by the carbonyl functionality in synthetic transformations, reacquisition of such a reaction site translates into heightened chemical versatility. The trajectories followed by vinyl organometallics as they engage in 1,2 addition to ketones are gradually being understood. Proper diastereoselective control of this bond-making process, when coupled with full awareness of the chair or boat topography adopted during the ensuing oxy-Cope electronic reorganization, provides for exciting new strategy-level dimensions not often available in other contexts. The use of this two-step sequence as a prelude to a third chemical event clearly serves to expand the possibilities for molecular construction still more. While a considerable amount of the work to date has focused on the preparation of rather elaborate carbocyclic molecules, principally with a view to gaining access to complex natural products, the possibilities for heterocyclic synthesis are currently being accorded increased attention.     

Acyl Iodides in Organic Synthesis: II. Reactions with Acyclic and Cyclic Ethers

Reaction of acyl iodides RCOI (R = Me, Ph) was studied with acyclic and cyclic ethers (Et₂O, MeCHCH₂(O), ClCH₂CHCH₂(O), THF, O(CH₂CH₂)₂O, EtOCH₂CH₂OH, EtOCH = CH₂, PhOEt]. The reaction occurred with the rupture of one or two CO bonds furnishing the corresponding iodides and esters.     

Preparation and Reactivity of Acyclic Chiral Allylzinc Species by a Zinc‐Brook Rearrangement

The zinc‐Brook rearrangement of enantiomerically enriched α‐hydroxy allylsilane produces a chiral allylzinc intermediate, which reacts with retention of configuration in the presence of an electrophile. Two remarkable features of this transformation are the stereochemical outcome during the formation of the allylzinc species and the complete stereocontrol in the organized six‐membered transition state, which leads to an overall and complete transfer of chirality within the reaction sequence.     

Cyclic and Acyclic N═N Bonds in Reactions with Some Alkenes and Dienes

The kinetics of the Diels–Alder (DA) reactions of 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione 1 , trans‐diethyl azodicarboxylate 2 , and tetracyanoethene 3 with 1,3‐cyclohexadiene 4 , cycloheptatriene 5 , 1,3‐cycloheptadiene 6 , cyclooctatetraene 7 , and 1,3‐cyclooctadiene 8 in a range of temperatures and pressures has been studied. Values of the enthalpy, entropy, and volume of activation, as well as the enthalpy and volume of reaction have been obtained. Observed reaction rates of 5+1 and 7+1 have been compared with the known rate of norcaradiene 17 formation in the equilibrium , and that of bicyclo[4,2,0]‐octa‐2,4,7‐triene 20 in the equilibrium . The kinetic data show that the rate of formation of 17 from 5 is much greater than the loss rate of dienophile 1 in reaction of 5+1 . In contrast, the formation rate of tautomer 20 is less than the loss rate of dienophile 1 in reaction of 7+1 . This reflects that the consecutive reaction of 5 → 17 (+ 1 ) → 15 is possible whereas the consecutive reaction of 7 → 20 (+ 1 ) → 22 does not occur as the only way.     

Phosphorylated Aminoacetal in the Synthesis of New Acyclic,Cyclic, and Heterocyclic Polyphenol Structures

New phosphorylated aminoacetal has been synthesized by the Kabachnik–Fields reaction; its reactivity has been studied in acid‐catalyzed condensation with linear polyphenols (2‐methylresorcinol, resorcinol, pyrogallol) and the Mannich reaction with macrocyclic polyphenol (calix[4]resorcinol). It has been determined for the first time that acid‐catalyzed reaction of phosphorus‐containing acetal with resorcinol and its derivatives in ethanol in the presence of hydrochloric acid gives new phosphorylated piperazines in addition to the compounds of diarylmethane series. Condensation of macrocyclic polyphenol (calix[4]resorcinol) with formaldehyde and N‐((dihexylphosphoryl)methyl)‐2, 2‐dimethoxyethylamine (the Mannich reaction) has resulted in novel tetrasubstituted calixarene containing aminophosphine oxide and acetal groups on the “upper rim” of molecule.     

Relationship between Activation Energy of Thermolysis and Friction Sensitivity of Cyclic and Acyclic Nitramines

The knowledge of sensitiveness of an energetic compound to friction stimuli is important to ensure the safety of people and protection of property during shipment. The information on sensitivity to friction is considered very valuable for nitramines, which show relatively higher sensitivity with respect to the other classes of secondary explosives. This study presents a novel general simple model for prediction of the relationship between friction sensitivity and activation energy of thermolysis of cyclic and acyclic nitramines on the basis of their molecular structures. This methodology assumes that friction sensitivity of an energetic compound with general formula C_aH_bN_cO_d can be expressed as a function of activation energy of thermolysis and the contribution of specific molecular structural parameters. For 21 nitramines with different molecular structures, the new correlation has the root mean square and the average standard deviations of 14.2 and 17.8 N, respectively, as compared to experimental values. The proposed new method is also tested for further 8 nitramines containing complex molecular structures, which gives good predictions.     

Syntheses and Characterization of Ten-Membered Cyclic and Large Bite Acyclic Bis(phosphines)

Reaction of bis(dichlorophosphino)aniline with CH 2 bridged bis(phenols) or substituted diamine gives the 10-membered heterocyclic phosphorochloridities in quantitative yield. The bis(phenols) also react with chlorodiphenylphosphine to afford the bulky acyclic bis(phosphinites).     

Copper-Catalysed Rearrangement of Cyclic Ethynylethylene Carbonates: Synthetic Applications and Mechanistic Studies

Transition-metal-catalysed reactions of cyclic ethynylethylene carbonates have been intensively studied because of their robustness in new bond formation and diversified molecule construction. Known reaction modes usually involve a substitution step occurring at either the propargylic or terminal alkyne positions. Here, we report an unprecedented reaction pattern in which cyclic ethynylethylene carbonates first undergo a rearrangement to release allenal intermediates, which subsequently react with diverse nucleophiles to furnish synthetically useful allylic and propargylic allenols, phosphorus ylides, and cyclopropylidene ketones through an addition process rather than a substitution pathway. The products enable various further transformations, and mechanistic studies and theoretical calculations reveal that the reaction does not proceed via a semipinacol type [1,2]-hydride shift, but through base-mediated deprotonation as the key step to induce the rearrangement.