Synthesis of α,β-Unsaturated Nitriles from the Iodine Catalyzed Reaction of Chloroacetonitrile with Aldehydes Promoted by Tri-n-Butylarsine and Magnesium

α,β-Unsaturated nitriles were synthesized from the iodine catalyzed reaction of chloro-acetonitrile with aldehydes promoted by tri-n-butylarsine and magnesium.     

Acid‐Promoted Ring Opening of α‐Hydroxyl Cyclobutanones: A Novel and Facile One‐Pot Synthesis of Nitrile Derivatives

A facile one‐pot synthesis of nitriles via a ring‐opening reaction of cyclobutanone adducts with hydroxylamine hydrochloride was developed.     

Reductive Amination of Glycosyl Aldoses: Synthesis of N‐Glycosylated β‐Glycosyl Amino Alcohols and their Enzyme Inhibitory Effect

Abstract

Reductive amination of glycosyl aldehydes (1a–c, 2) with glycosyl amino esters (3a–c, 4) in the presence of sodium borohydride gave diglycosylated amino esters (5–15) in good yield. N‐Glycosyl‐glycosylated amino esters were reduced to the respective diglycosyl amino alcohols (16–26) with LiAlH₄ in good yield. All the synthesized compounds were studied for their inhibitory effect, if any, against hepatic glucose‐6‐phosphatase, glycogen phosphorylase, and intestinal brush border membrane α‐glucosidase; among these compounds 7, 21, and 25 have shown marked inhibition on these enzymes, respectively.     

Synthesis of the C‐Glycoside of Methyl α‐d‐Altropyranosyl‐(1→4)‐α‐d‐glucopyranoside

The C‐glycoside of methyl α‐d‐altropyranosyl‐(1→4)‐α‐d‐glucopyranoside 2 was prepared in a convergent fashion, from readily available precursors, 4‐O‐tert‐butyldiphenylsilyl‐1,2‐O‐isopropylidene‐d‐erythro‐S‐phenyl monothiohemiacetal 13 (five steps from D‐ribose) and the known acid, methyl 2,3,6‐tri‐O‐benzyl‐4‐C‐(carboxymethyl)‐4‐deoxy‐α‐d‐glucopyranoside 17 (seven steps from methyl α‐d‐glucopyranoside). The key reactions in the synthesis are the oxocarbenium ion cyclization of thioacetal‐enol ether 19 to a C1 substituted glycal 20, and the stereoselective hydroboration of 20 to the α‐C‐altroside 21.     

Hypervalent Iodine in Synthesis XXX: Palladium-Catalyzed Reaction of Diaryliodonium Salts with β-substituted-α, β-enones

The reaction of diaryliodonium salts with β-substituted-α,β-enones in the presence of a palladium catalyst affords H_β-substituted products with excellent yields.     

Facile Synthesis of E‐Diiodoalkenes: H2O2‐Activated Reaction of Alkynes with Iodine

Hydrogen peroxide was found to activate iodine in the addition reaction with triple bonds. A facile and technologically straightforward procedure was developed for the synthesis of E‐diiodoalkenes based on the reaction of alkynes with an I₂–H₂O₂ system in THF. Selective iodination of terminal and internal alkynes containing electron‐donating and electron‐withdrawing substituents afforded 16 E‐diiodoalkenes in yields up to 89%.     

Synthesis of β‐Lactams: α‐Chloro and α‐Cyano β‐Lactams by Condensation of Imines with Titanium Ester Enolates Derived from Chloro and Cyano Ethyl Acetates

Abstract

α‐Cyano and α‐chloro β‐lactams are obtained in a one‐step reaction at a temperature of less than ?78°C by condensation of imines with ester enolates derived from ethyl α‐cyano and α‐chloro acetates.     

Synthesis of β-Glucosides with 3-O-Picoloyl-Protected Glycosyl Donors in the Presence of Excess Triflic Acid: A Mechanistic Study

Our previous study showed that picoloylated donors are capable of providing excellent facial stereoselectivity through the H-bond-mediated aglycone delivery (HAD) pathway. Presented herein is a detailed mechanistic study of stereoselective glycosylation with 3-O-picoloylated glucosyl donors. While reactions of glycosyl donors equipped with the 3-O-benzoyl group are typically non-stereoselective because these reactions proceed via the oxacarbenium intermediate, 3-O-picoloylated donors are capable of providing enhanced, but somewhat relaxed, β-stereoselectivity by the HAD pathway. In an attempt to refine this reaction, we noticed that glycosylations are highly β-stereoselective in the presence of NIS and stoichiometric TfOH. The HAD pathway is highly unlikely because the picoloyl nitrogen is protonated under these reaction conditions. The protonation and glycosylation were studied by low-temperature NMR, and the intermediacy of the glycosyl triflate has been observed. This article is dedicated to broadening the scope of this reaction in application to a variety of substrates and targets.     

Regioselective Synthesis of 6‐Prenylpolyhydroxyisoflavone (Wighteone) and Wighteone Hydrate with Hypervalent Iodine

The oxidative rearrangement of 3′‐iodotetraalkoxychalcone with [hydroxyl(tosyloxy)iodo]benzene, followed by cyclization of the resultant acetal gave 6‐iodotrialkoxyisoflavone. The coupling reaction of the isoflavone with 2‐methyl‐3‐butyn‐2‐ol gave 6‐alkynylisoflavone, whose hydrogenation gave wighteone hydrate. Wighteone was synthesized by dehydration of wighteone hydrate.     

Room‐Temperature Ionic Liquid–Promoted Williamson's Synthesis of Ethers: A Facile Synthesis of Diaryloxymethanes

A simple and efficient method has been developed for the synthesis of phenolic ethers using room‐temperature ionic liquid, not only as solvent but also as promoter. Ionic liquid was recycled and subsequently reused without any loss of the product.     

Synthetic Studies on Sialoglycoconjugates 60: α-Stereocontrolled,Glycoside Synthesis of Trimeric Sialic Acid with Galactose and Lactose Derivatives

Abstract

α-Stereocontrolled, glycoside synthesis of trimeric sialic acid is described toward a systematic approach to the synthesis of sialoglycoconjugates containing an α-sialyl-(2→8)-α-sialyl-(2→8)-sialic acid unit α-glycosidically linked to O-3 of a galactose residue in their oligosaccharide chains. Glycosylation of 2-(trimethylsilyl)ethyl 6-O-benzoyl-β-d-galactopyranoside (4) or 2-(trimethylsilyl)ethyl 2,3,6,2′,6′-penta-O-benzyl-β-lactoside (5), with methyl [phenyl 5-acetamido-8-O-[5-acetamido-8-O-(5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylono-1”, 9′-lactone)-4,7-di-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylono-1′, 9-lactone]-4,7-di-O-acetyl-3,5-dideoxy-2-thio-d-glycero-d-galacto-2-nonulopyranosid]onate (3), using N-iodosuccinimide-trifluoromethanesulfonic acid as a promoter, gave the corresponding α-glycosides 6 and 8, respectively. The glycosyl donor 3 was prepared from trimeric sialic acid by treatment with Amberlite IR-120 (H⁺) resin in methanol, O-acetylation, and subsequent replacement of the anomeric acetoxy group with phenylthio. Compounds 6 and 8 were converted into the per-O-acyl derivatives 7 and 9, respectively.     

Tetra‐n‐butylammonium Hydroxide (TBAH)–Catalyzed Knoevenagel Condensation: A Facile Synthesis of α‐Cyanoacrylates, α‐Cyanoacrylonitriles,and α‐Cyanoacrylamides

Tetra‐n‐butylammonium hydroxide (TBAH) has been utilized as a novel and efficient catalyst for the Knoevenagel condensation of aldehydes with acidic methylene compounds such as methyl‐ and ethylcyanoacetate, malononitrile, and cyanoacetamide to afford substituted olefins.     

Synthesis of 1,3-Diketones by Reaction of α-Haloketones with Acyl Cyanides Promoted by Samarium Diiodide

α-Haloketones reacted with acyl cyanides to form 1,3-diketones in the presence of samarium diiodide. The reaction was assumed to proceed via a mechanism involving samarium enolates formed in situ from α-haloketones.     

Facile Synthesis of Amidines via Intermolecular Reductive Coupling of Nitriles with Azobenzene Promoted by Samarium Diiodide

SinceintroducedbyKaganandhisgroups',Sml,hasbeenextensivelyinvestigatedasamild,neutral,selectiveandversatilesingIeelectrontransferreductantinsyntheticchemistry=.Suchas,Barbierreactions,Reformatskyreactions,pinacolcouplingandketone-oIefinreductivehavebeenreportedusingSmI,asreagent.Thereactivitiesofvariousnitrogenfunctionalgroups(imine,oxime,nitro,azo,cyano)towardsSmI,havealsobeenexamined.Recently,ourgrouphasreportedtheintermolecularreductivecouplingofnitrogroupswithcyanogroupsinducedbySml='.…     

Gold-Catalyzed Cadiot–Chodkiewicz-type Cross-Coupling of Terminal Alkynes with Alkynyl Hypervalent Iodine Reagents: Highly Selective Synthesis of Unsymmetrical 1,3-Diynes

A new and efficient method for the synthesis of unsymmetrical 1,3-butadiynes by gold-catalyzed C(sp)–C(sp) cross-coupling of terminal alkynes with alkynyl hypervalent iodine(III) reagents has been developed. The reaction features high selectivity and efficiency, mild reaction conditions, wide substrate scope, and functional-group compatibility, and is a highly attractive complement to existing methods. Mechanistic studies reveal that formation of a phenanthrolinyl-ligated gold(I) complex is crucial for the efficiency and selectivity of the target transformation.     

Synthetic Studies on Sialoglycoconjugates 16: α-Predominant Glycoside Synthesis of N-Acetylneuraminic Acid With the Primary Hydroxyl Group in Carbohydrates Using Dimethyl(Methylthio)Sulfonium Triflate as a Glycosyl Promoter

ABSTRACT

Coupling of the primary hydroxyl group in the suitably protected 2-(trimethylsilyl)ethyl glycosides of D-glucopyranose (3), N-acetyl-D-glucosamine (7), N-acetyl-D-galactosamine (9), D-lactose (10), and N-acetylneuraminic acid (11), with methyl (methyl 5-acetamido-4, 7,8, 9-tetra-O-acetyl-3, 5-dideoxy-2-thio-D-glycero-α-D-galacto-2-nonulopyranosid)onate (12) as the glycosyl donor in acetonitrile in the presence of dimethyl(methylthio)sulfonium triflate (DMTST) as a glycosyl promoter and molecular sieves 3A, gave predominantly the corresponding α-glycosides 13, 15, 17, 25, and 29 of N-acetylneuraminic acid in 43-71% yields, respectively, together with the ß-glycosides (13-24%).     

α,α‐Dibromoketones: A Superior Alternative to α‐Bromoketones in Hantzsch Thiazole Synthesis

Abstract

α,α‐Dibromoketones (2) have been found to be a superior alternative to the conventionally used α‐bromoketones (1) for performing the Hantzsch thiazole synthesis.1 Ahluwalia, V. K., Mehta, B. and Rawat, M. 1992. Synth. Commun., 22: 2697[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar] These crystalline, nonlachrymatory compounds are more reactive than 1 as demonstrated by their reaction with 3,5‐dimethyl‐1‐thiocarboxamide (5).     

Synthesis,Spectroscopic and Computational Studies of CT Complexes of Amino Acids with Iodine as σ Acceptor

Understanding the charge transfer process between bioactive molecules and inorganic or organic molecules is significant as this interaction can be used to interpret bioactive molecule–receptor interactions. A comprehensive spectrophotometric study has been performed to explore the complexation chemistry of the amino acids, tyrosine, lysine and arginine, with iodine as σ acceptor. The molecular structure, spectroscopic characteristics and the interactive modes have been deduced from UV–Vis and IR spectra. The binding ratio of complexation has been determined to be 1:1 for iodine with the amino acids. The association constant (K), extinction coefficient (ε _max), ionization potential (IP), energy of the charge transfer complex (E _CT), resonance energy (R _N ), dissociation energy (W) and standard Gibbs energy (ΔG°) have been computed. An in silico study has been carried out using GAMESS computations to understand the structural features. Highest occupied molecular orbital and lowest unoccupied molecular orbital calculations helped us in characterizing the chemical reactivity and kinetic stability of the molecules. A good consistency between experimental and computational results has been found.     

Cerium(III) Chloride: A Highly Efficient Reagent for the Synthesis of α‐Aminonitriles

We report a highly efficient, one‐pot, three‐component condensation of carbonyl compounds, amines, and TMSCN in MeCN; the reaction is significantly promoted by the catalytic amount of cerium(III) chloride at ambient temperature in excellent yields without any adverse effect on the other substituents. The method afforded an elegant alternative to the synthesis of α‐aminonitriles. The reactions are fast and clean, and the products obtained are of high purity.     

Single-Pot Synthesis of Spiroannulated Dihydrofurans by Iodine–Ammonium Acetate–Mediated Reaction of Dimedone with Aldehydes

Iodine–ammonium acetate–mediated annealation of dimedone with aldehydes led to facile formation of spirodihydrofuran in good yields through tandem Knoevenagel–Michael iodonation and cyclodehydroiodonation reactions in a single pot.