7α-alkylation, 7,7-bisalkylation,and reduction of the 20-oxo group of poststerone in reactions with alkyl halides in lithium–ammonia solution

Reactions of poststerone with methyl iodide, allyl bromide, and propargyl bromide in lithium–ammonia solution resulted in its completely stereoselective 7α-alkylation accompanied by reduction of the 20-oxo group with formation of equimolar amounts of 20R- and 20S-hydroxy derivatives. The reaction of poststerone with excess allyl bromide afforded 7,7-bis-allyl 20R- and 20S-alcohols at a ratio of 3: 1. The reduction of the 20-oxo group in the alkylation of poststerone with excess propargyl bromide led to the formation of an equimolar mixture of Δ⁸⁽¹⁴⁾- and Δ⁸⁽⁹⁾-isomers with exclusive S configuration of C²⁰.     

Lead-promoted Barbier-type reaction of aldehydes with propargyl bromides in aqueous media

This paper reports that the reaction of the propargyl bromides with aldehydes promoted by powdered lead in aqueous media.The selectivity and possible mechanism of these reactions are discussed.The yields of products for reaction of propargyl bromide are 31~71%.The ratios of al-lenyl alcohol and homopropargyl alcohol are 1:1.5 to 1:3.The product for reaction of phenyl propargyl bromide is allenyl alcohol and the yields are 52~84%.     

An Efficient Approach for the Synthesis of 1,2,3‐Triazole Moiety to Generate Uracil Molecular Architectures Through Cu‐Catalyzed Azide–Alkyne Cycloaddition

A simple and efficient pathway to tether conjugates of monosaccharides or aromatic moieties to uracil establishing a 1,2,3‐triazole linker via click chemistry was reported. The reaction of arylimines of 5‐amino uracil with propargyl bromide in a basic medium gave a di‐propargylated uracil. The latter compound was converted into molecular architectures containing bis‐1,2,3‐triazole rings through Cu‐catalyzed 1,3‐cycloaddition reaction with different azides. The same arylimine of 5‐amino uracil yielded different products under reflux with propargyl bromide in acetonitril with the majority to 6‐propargylated‐5‐amino uracil.     

Synthesis of [1,3]Thiazolo[2,3-i]purinium Systems

Russian Journal of Organic Chemistry - The alkylation of purine-6-thiol with methallyl chloride and propargyl bromide in aqueous alcohol in the presence of alkali gave...     

Probing the Lewis Acidity of Boronic Acids through Interactions with Arene Substituents

Boronic acids are Lewis acids that exist in equilibrium with boronate forms in aqueous solution. Here we experimentally and computationally investigated the Lewis acidity of 2,6-diarylphenylboronic acids; specially designed phenylboronic acids that possess two flanking aromatic rings with tunable aromatic character. Hammett analysis of 2,6-diarylphenylboronic acids reveals that their Lewis acidity remains unchanged upon the introduction of EWG/EDG at the distant para position of the flanking aromatic rings. Structural and computational studies demonstrate that polar-π interactions and solvation effects contribute to the stabilization of boronic acids and boronate forms by aromatic rings. Our physical-organic chemistry work highlights that boronic acids and boronates can be stabilized by aromatic systems, leading to an important molecular knowledge for rational design and development of boronic acid-based catalysts and inhibitors of biomedically important proteins.     

Alkylation of nido-7,8-Dicarbollide Anion with Propargyl Bromide in Liquid Ammonia with Formation of 8-Propargyl-nido-7,9-dicarbaundecaborate and 9-Propargyl-nido-7,8-dicarbaundecaborate Anions

Alkylation of nido-7,8-dicarbollide anion with propargyl bromide in liquid ammonia is accom panied by skeleton rearrangements and yields, depending on the reaction conditions, 8-propargyl-nido-7,9-dicarbaundecaborate or 9-propargyl-nido-7,8-dicarbaundecaborate anion.     

One-pot, solvent-free regioselective addition reactions of propargyl bromide to carbonyl compounds mediated by Zn-Cu couple

A Barbier-type propargylation of carbonyl compounds with propargyl bromide has been achieved with reactive zinc-copper couple under solvent-free conditions. The reaction of aldehydes with propargyl bromide produced the unique homopropargyl alcohols in excellent yields at room temperature without the formation of homoallenyl alcohols. The ketones reacted with propargyl bromide to give the corresponding homopropargyl alcohols in good to excellent yields at −14 to −16 °C. The advantages of this method are excellent yields, short reaction time, high regioselectivity, and avoidance of the use of organic solvents.     

Zinc-Promoted Barbier-Type Reaction of Propargyl Bromide with Aldehydes in Aqueous Media

In the prese of metallic zinc, propargyl bromide is found to react with aldehydes at room temperature in tetrahydrofurane-saturated aqueous ammonium chloride (5:2) to afford the corresponding homopropargylic alcohols in moderate to high yields together with small amounts of α-allenic alchohols.     

锡存在下取代的炔丙基溴与醛反应的选择性

报道三甲基硅基和苯基取代的炔丙基溴在锡存在下与醛的反应, 并讨论了反应的选择性。三甲基硅基炔丙基溴与醛的反应产率约为71-84%。产物中丙二烯醇与高炔丙基醇之比在44 :56到25 : 75之间, 苯基炔丙基溴的反应得到了产物丙二烯醇。     

锡-铟促进和微波辐射辅助下醛和炔丙基溴的炔丙基化反应

A rapid and regioselective preparation of homopropargyl alcohols was reported. In the presence of SnCl2C6HsMe3NBr and microwave irradiation, the mixture of tin-indium and propargyl bromide reacted quickly with aldehydes in aqueous media to produce the homopropargyl alcohols exclusively in high yields. For benzaldehydes bearing different substituents, electronic effect of the substituents affected the reaction, the electron-withdrawing groups promoting the reaction and the electron-donating groups impeding the reaction. The reactions of benzaldehydes bearing an ortho substituent group on the phenyl ring with propargyl bromide may yield a mixture of regioisomers （homopropargyl and homoallenyl alcohols） or a single homoallenic alcohol due to the steric effect.     

Regioselective Propargylation of Aldehydes with Propargyl Bromide Mediated by Sn-In in Aqueous Media under Microwave Irradiation

Tin-indium were employed in the propargylations of various aldehydes with propargyl bromide in the presence of SnCl2 and C6H5（CH3）3NBr under microwave irradiation to afford the corresponding homopropargyl alcohols exclusively in high yields. All the reactions were completed smoothly in predominantly aqueous media in 200 seconds only.     

Photorearrangement of Propargyl Bromide as a Probe to Study Propargylic and Allenic Radicals by Infrared Matrix Isolation Technique

The photolysis of propargyl bromide in Ar matrix to form allenyl bromide proceeded with a radical mechanism. The deuterium label study and radical scavenger were used to investigate the mechanism. Neither propargyl nor allenyl radical was trapped in Ar matrix at 8 K. The rates of propargyl and allenyl radicals coupled with bromo radical are significantly fast. The stability of propargyl and allenyl radicals is discussed.     

Asymmetric indium-mediated synthesis of homopropargylic alcohols

A method for the enantioselective synthesis of homopropargylic alcohols using indium under Barbier-like conditions is reported herein. Both aromatic and aliphatic aldehydes were successfully converted to the corresponding homopropargylic alcohols in good yield and high enantiomeric excesses using propargyl bromide, indium, and (1S,2R)-(+)-2-amino-1,2-diphenylethanol as a chiral auxiliary.     

A facile synthesis of fused aromatic spiroacetals based on the 3,4,3′,4′-tetrahydro-2,2′-spirobis(2H-1-benzopyran) skeleton

The facile synthesis of a series of aromatic 6,6-spiroacetals based on the parent 3,4,3′,4′-tetrahydro-2,2′-spirobis(2H-1-benzopyran) heterocyclic system is reported. Key steps included the use of a Sonogashira coupling for the synthesis of an aryl acetylene that was coupled to an aryl aldehyde to form a propargyl alcohol intermediate. Hydrogenation of the alkynol followed by oxidation produced a masked dihydroxy ketone that upon treatment with trimethylsilyl bromide underwent deprotection and cyclisation to the fused aromatic spiroacetal.     

Ferrous Sulfide/Aqueous Ammonia: Simple,Efficient, and Chemoselective Reagent for the Conversion of Aromatic Azide to Amine

A practical, environmentally benign, rapid, and efficient method for the reduction of aromatic azide to amine is described using FeS/aqueous ammonia in the presence of other reducible functionalities. Application of a novel reducing reagent results in aromatic amines with excellent yield and high chemoselectivity, without need of any purification techniques.     

Structures of carbohydrate-boronic acid complexes determined by NMR and molecular modelling in aqueous alkaline media

The structures of thermodynamically stable aromatic boronic acid : cyclic carbohydrate chelates in aqueous alkaline media have been studied using 1H NMR spectroscopy and molecular modelling. It is found that interacting saccharides must necessarily possess a synperiplanar diol functionality for complexation to occur. While this is possible for furanose structures which tend to have a puckered planar geometry, for pyranose forms it is postulated that bis-complexation occurs with twist conformers of the pyranose ring, providing the ring has the requisite 1,2 : 3,4 polyol stereochemistry; specifically axial,equatorial : equatorial,axial or equatorial,axial : axial,equatorial orientations. In this respect it is possible to be predictive with regard to individual carbohydrate boronic acid interactions and to give reasonably comprehensive structural assignments to complexed components. In this paper twenty four polyhydroxy compounds have been screened using 1H NMR to monitor complexation along with computational techniques on a model system to substantiate proposed structures. It has been found that all of these materials interact with aromatic mono boronic acids as expected and structures for the resulting chelates are proposed.     

Palladium-catalyzed aminocarbonylation of aryl iodides using aqueous ammonia

Aminocarbonylation of aromatic iodides using aqueous ammonia in toluene has been developed. Various primary aromatic amides have been efficiently synthesized in good to excellent yields in the presence of catalytic quantities of Pd(OAc)₂/CYTOP®292. The usage of aqueous ammonia avoids the handling of two gases in the reaction.     

Tandem synthesis of aromatic amides from styrenes in water

An expedient one-pot synthesis of aromatic amides has been reported from styrenes in the presence of N-bromosuccinimide and iodine by using aqueous ammonia in water. The reaction proceeds through the formation of α-bromoketone as an intermediate in the presence of NBS and water. α-Bromoketone on reaction with iodine forms bromodiiodoketone which on nucleophilic substitution with aqueous ammonia gives aromatic amide. Substituted aromatic amides were obtained in good yields with wide functional group compatibility.     

Indium-mediated vic-diallylation/propargylation of phenacyl bromides: a facile synthesis of 4-arylocta-1,7-dien-4-ol derivatives

Phenacyl bromides undergo smooth vic-diallylation and dipropargylation with allyl and propargyl indium reagents generated in situ from metallic indium and allyl or propargyl bromide to produce 4-arylocta-1,7-dien-4-ol derivatives in good yields. Phenacyl chloride and azide also participated effectively in bis-allylation. Similar results are also obtained from in situ generated allyl or propargyl zinc bromide.     

Experimental and theoretical studies of the propargyl-allenylindium system

The transient organoindium intermediates formed in the reaction of propargyl bromide with indium in aqueous media and tetrahydrofuran were investigated by NMR spectroscopy and found to be allenylindium(I) and allenylindium(III) dibromide. The influence of solvent and methyl substitution on the propargyl-allenylindium system was also studied. The experimental observations were supported by theoretical calculations using the B3LYP/6-311+G* method.