Mediated Addition Reaction Research Articles

Facile Synthesis of Liquid Crystal Dimers Bridged with a Phosphonic Group.

Liquid crystal (LC) dimers with well-defined composition and structure arouse broad attentions for their exhibiting LC properties beyond conventional low molar mass mesogens and serving as fascinating model compounds for LC polymers. Here in this work, a series of LC dimers bridged with a phosphonic group have been synthesized through a facile free radical mediated addition reaction between hypophosphorous acid and vinyl terminated cyanobiphenyl mesogens with variant length alkyl spacers. In addition, two esterified derivatives and a group of mono-addition homologues with a terminal phosphonic acid group have also been prepared for comparison study. All the newly synthesized compounds exhibit monotropic nematic (N) phase with typical schlieren textures except for the LC dimer with the longest eleven-methylene spacer, which surprisingly shows twist-bend nematic (NTB ) phase directly from the isotropic state upon cooling. Moreover, the thermal transition properties such as the nematic-isotropic transition temperatures and associated entropy changes of the series LC dimers display a modest odd-even effect. Furthermore, both the LC dimers and the mono-addition homologues in N phase are quite easy to achieve homeotropic alignment upon annealing thanks to the supramolecular interactions between the introduced phosphonic acid group and the hydroxylated glass surface. This work thus provides a novel synthesis strategy for a class of LC materials bridged with a phosphonic acid group prone to further functionalization, which may serve as promising vertical alignment agents and pave the way for developing a new kind of functionalized LC materials of NTB phase.

Mn(OAc)3-Mediated Addition Reactions of NaSO2CF3 and Perhalogenated Carboxylic Acids with Unactivated Alkenes Conjectured by a Single Electron Transfer and Halogen Abstraction Mechanism

A free-radical halotrifluoromethylation of olefins by using Mn(OAc)3·2H2O, CF3SO2Na, and perhalogenated carboxylic acids has been achieved. Perhalogenated carboxylic acids act as a halogen source and CF3SO2Na acts as a CF3 source. The reaction displayed good tolerance of functional groups in the substrates under mild conditions. The radical clock experiment and TEMPO inhibition experiment support a radical process. The halogen reagent competition experiment shows that the last step of halogenation process is mainly through a halogen abstraction mechanism.

ChemInform Abstract: Zinc‐Mediated Addition of Bromoacetonitrile to Carbonyl Compounds under Solvent‐Free Conditions.

Zinc mediated addition reaction of bromoacetonitrile with aryl aldehydes and ketones produces β-hydroxynitriles under solvent-free conditions. The valuable feature of the methodology are solvent-fr...

BF3-Mediated Oxidative Cross-Coupling of Pyridines with Alkynyllithium Reagents and Further Reductive Functionalizations of the Pyridine Scaffold

A set of functionalized alkynylpyridines can be readily obtained using Et₂O·BF₃ as promoter. Alkynyllithium reagents undergo an addition reaction at position C-2 of pyridines that are rearomatized by oxidative treatment with chloranil. These substituted pyridines can be easily converted into more valuable intermediates. Examples of applications are given as well. Finally, the synthesis of piperidines and lactams via first an oxidative BF₃-mediated addition reaction followed by a NaBH₄ reduction or acidic workup is also described.

Zinc-mediated Addition of Bromoacetonitrile to Carbonyl Compounds under Solvent-free Conditions

Zinc mediated addition reaction of bromoacetonitrile with aryl aldehydes and ketones produces β-hydroxynitriles under solvent-free conditions. The valuable feature of the methodology are solvent-free and catalyst-free conditions and short reaction times (5 min).

Transition-metal chloride mediated addition reaction of diorganomagnesium to easily enolizable ketones

An alkylation to an easily enolizable ketone, such as β-tetralone, is difficult to perform with Grignard reagent (RMgX) or with diorganomagnesium (R 2Mg), because a deprotonation to form a magnesium enolate occurs predominantly. To avoid the prior enolization, a complex reagent of a transition-metal salt and R 2Mg was examined: A combination of R 2Mg with iron(II) chloride (FeCl 2) or ytterbium(III) chloride (YbCl 3) gave a complex reagent that can realize a nucleophilic reaction to β-tetralone prior to the enolization. A combination of RMgX with these metal salts is inferior to a combination of R 2Mg with them to obtain the nucleophilic complex reagent.

Stereoselective Reactions of (E,E)‐2,3,6,7‐Tetramethyl‐1,8‐Bis(trimethylsilyl)octa‐2,6‐diene with Aldehydes and Acyl Chlorides

AbstractThe titanium tetrachloride mediated addition reaction of (E,E)‐2,3,6,7‐tetramethyl‐1,8‐bis(trimethylsilyl)octa‐2,6‐diene to aldehydes and acyl chlorides is described. Aldehydes undergo simple allylation except p‐anisaldehyde, which leads to cyclopentane resulting from double allylation. From acyl chlorides, highly substituted meso cyclopentanols bearing 1,3‐diquaternary carbon atoms separated by a tertiarycarbinol are obtained. The structures of two cyclopentanols are confirmed by X‐ray analysis. From the structure of the cyclopentanols, a reaction mechanism for the double allylation of the acyl chloride by diallylsilane could be proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Copper(II) Triflate—Mediated Addition Reaction of α‐Oxygenated Alkylsilanes to Imines for the Synthesis of Vicinal‐Amino Alcohols.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Copper(II) Triflate–Mediated Addition Reaction of α‐Oxygenated Alkylsilanes to Imines for the Synthesis of Vicinal‐Amino Alcohols

In the presence of copper(II) triflate, the addition reaction of α‐oxygenated alkylsilanes to several imines proceeded smoothly to give the corresponding vicinal‐amino alcohols in moderate yields.

Synthesis of Some 2‐Aminonitroethanes via Tin(II)chloride Mediated Addition Reaction of Bromonitromethane to Imines.

Synthesis of Some 2‐Aminonitroethanes via Tin(II)chloride Mediated Addition Reaction of Bromonitromethane to Imines.

Tin(II) Chloride Mediated Addition Reaction of Bromonitromethane to Aldehydes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of Some 2-Aminonitroethanes via Tin(II)chloride Mediated Addition Reaction of Bromonitromethane to Imines

In the presence of tin(II)chloride, bromonitromethane reacts with imines derived from aromatic aldehydes and ammonia to yield 2-amino-2-aromatic substituted nitroethane derivatives via an addition reaction in good yields.

Tin(II)chloride Mediated Addition Reaction of Bromonitromethane to Aldehydes

Bromonitromethane adds to aliphatic aldehydes in the presence of tin(II) chloride to yield β -nitro alcohols via a Reformatsky-type reaction in high yields, while aromatic aldehydes give low yields. The products were characterized by IR, NMR, and mass spectroscopy and by elemental analysis

Copper(II) Triflate Mediated Addition Reaction of α‐Oxygenated Alkylstannanes to Imines for the Synthesis of vicinal‐Amino Alcohol Derivatives.

In the presence of copper(II) triflate, a novel addition reaction of α-oxygenated alkylstannanes to various kinds of imines proceeded smoothly to give the corresponding vicinal-amino alcohol derivatives in good yield.

SmI2‐Mediated Addition Reaction of α‐Halomethylsulfones to Carbonyl Compounds. A Convenient Synthesis of β‐Hydroxysulfones

AbstractDue to the chemoselective dehalogenation by SmI2, the addition of α‐halomethylsulfones to carbonyl compounds afforded β‐hydroxysulfones. Those reactions with α‐bromomethylsulfones gave the products in moderate to good yields. The SmI2‐mediated addition of gem‐dihalomethylsulfones to ketones also afforded α‐halo‐β‐hydroxysulfones in moderate yields.

ChemInform Abstract: Diastereoselectivity Control in the TiCl4‐Mediated Addition Reaction of Allyltrimethylsilane to N,O‐Protected (L)‐Serinals.

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.

New building blocks for efficient and highly diastereoselective polyol production—synthesis and utility of (R ′,R ′,S,S ) and (S′,S′,R,R)-2,3-butane diacetal protected butane tetrol derivatives

The efficient synthesis of aldehydes derived from 2,3-butane diacetal protected butane tetrols (S′,S′,R,R)-5 and (R′,R′,S,S)-6 and their utility in the controlled synthesis of polyhydroxylated materials through highly diastereoselective Lewis acid mediated addition reactions of allyltributylstannane and silyl enol ether nucleophiles is described.

ChemInform Abstract: Triethyloxonium Tetrafluoroborate Mediated Addition Reaction of Unsaturated Organosilanes to Squaric Acid Esters.

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.

Triethyloxonium Tetrafluoroborate Mediated Addition Reaction of Unsaturated Organosilanes to Squaric Acid Esters

Triethyloxonium Tetrafluoroborate Mediated Addition Reaction of Unsaturated Organosilanes to Squaric Acid Esters

A one-step control of four stereogenic centres during the Sakurai reaction of 1,8-bis(trimethylsilyl)octa-2,6-diene (BISTRO) to α,β-enones

The titanium tetrachloride mediated addition reaction of 1,8-bis(trimethylsilyl)octa-2,6-diene (BISTRO) with open-chain conjugated enones affords syn-anti-syn-4,7-divinyldecane-1, 10-diones with a very high diastereoselectivity.