Synthesis of an electrophilic keto-tetraene 15-oxo-Lipoxin A4 methyl ester via a MIDA boronate

15-oxo-Lipoxin A₄ (15-oxo-LXA₄) has been identified as a natural metabolite of the fatty acid signaling mediator Lipoxin A₄. Herein, we report a total synthesis of the methyl ester of 15-oxo-LXA₄ to be used in investigations of potential electrophilic bioactivity of this metabolite. The methyl ester of 15-oxo-LXA₄ was synthesized in a convergent 15 step (9 steps longest linear) sequence starting from 1-octyn-3-ol and 2-deoxy-d-ribose with Sonogashira and Suzuki cross-couplings of a MIDA boronate as key steps.     

A novel effective electrophile: β-trifluoroacetylketene diphenyldithioacetal S,S-tetroxide

A synthesis of a novel electrophilic reagent--β-trifluoroacetylketene diphenyldithioacetal S,S-tetroxide 3 is described. The reaction of 3 with various electron-rich aromatics such as 1,3-dimethoxybenzene, 2-methylthiophene, N-methylpyrrole, and 2-methylindole was investigated. In the course of these reactions an unusual migration of a phenylsulfonyl group takes place. An easy and ready for scale-up procedure for the synthesis of previously unknown β-aryl, α-phenylsulphonyl substituted α,β-unsaturated trifluoromethyl ketones is reported.     

Synthesis of ortho-substituted cyanopyridines through lithio intermediate trapping

Ortholithiation of 4-cyanopyridine using 2,2,6,6-tetramethylpiperidide (LiTMP) and trapping the lithio intermediate with electrophiles represents an efficient and straightforward access to ortho-substituted-4-cyanopyridines. The cyano group can be used as an ortho-directing group and allows the preparation of 3-halogeno-4-cyanopyridines. Reactivity of 2- and 3-cyanopyridines is also investigated and seems to give similar results.     

A sequence of electrophile induced cyclisation and concomitant N-deprotection of alkenylsulfinimines and alkenylsulfinamides as a direct route to cyclic or spirocyclic imines, pyrrolidines and piperidines

Alkenylsulfinimines and alkenylsulfinamides underwent electrophile induced cyclisation reactions with phenylselenyl bromide, iodine and bromine to cyclic and spirocyclic imines, pyrrolidines and piperidines with spontaneous cleavage of the protective group at nitrogen in good to excellent yield.     

Triphosphane formation from the terminal zirconium phosphinidene complex [Cp2Zr=PDmp(PMe3)] (Dmp=2,6-Mes2C6H3) and crystal structure of DmpP(PPh2)2

The new terminal phosphinidene complex [Cp₂Zr=PDmp(PMe₃)] (Dmp=2,6-Mes₂C₆H₃; 1) was prepared in 81% yield by the reaction of [Li(Et₂O)][P(H)Dmp] with [Cp₂Zr(Me)Cl] in the presence of excess PMe₃. Compound 1 reacts with Ph₂PCl to produce selectively the sterically congested triphosphane DmpP(PPh₂)₂ (2) and [Cp₂ZrCl₂] in high yields. The structure of 2 obtained by X-ray diffraction analysis of a single crystal reveals phosphorus–phosphorus bond lengths of 2.251(2) and 2.234(2) Å and a PPP bond angle of 105.46(6)°.     

An efficient route to diverse H-pyrazolo[5,1-a]isoquinolines via sequential multi-component/cross-coupling reactions

Multi-component reaction of 2-alkynylbenzaldehyde, sulfonohydrazide, electrophile (bromine or iodine), and ketone or aldehyde under mild conditions proceeds smoothly to afford the functionalized H-pyrazolo[5,1-a]isoquinolines in good yields. This one-pot process involves intermolecular condensation, electrophilic cyclization, nucleophilic addition, intramolecular condensation, and aromatization. The resulting halo-containing H-pyrazolo[5,1-a]isoquinolines could be further elaborated via palladium-catalyzed cross-coupling reactions.     

SYNTHESIS AND PROPERTIES OF SOME NEW,STABLE THIETES (THIACYCLOBUTENES)

Abstract

Simple alkyl substituted thietes are liquids which decompose at room temperature presumably via electrocyclic ring opening to give polymeric material.     

An Expeditious Synthetic Route to Carnosic Acid Type Diterpenes

2-Oxo-10-carboxy-8,11,13-podocarpatriene 7, a model for carnosic acid type diterpenes has been synthesized by an expeditious synthetic route.     

A Novel Initiator Containing Alkyne Group for the Polymerization of 2-Ethyl-2-oxazoline

A novel trifunctional initiator with one alkyne and two trifluoromethanesulfonate moieties was synthesized from a protected alcohol 5-hydroxyl-2-phenyl-1, 3-dioxane. The alkyne functionalized intermediate with two protected alcohol groups was synthesized by reacting with propargyl bromide. The alcohol groups were cleaved using a mixture of tetrahydrofuran and hydrochloric acid aqueous solution. In the last step the initiator was synthesized using triflic anhydride in carbon tetrachloride. The initiator was characterized by ¹H NMR and used for the polymerization of 2-ethyl-2-oxazoline which gives polymers with narrow distribution. For comparison a similar initiator with two tosylates was prepared and used for the polymerization of the monomer 2-ethyl-2-oxazoline, the resulting product has a wide molecular weight distribution and most of the initiator remains unreacted after 24 h which may be due to the steric hindrance between the two tosylate groups. To further explore the steric hindrance phenomenon, a linear tosylate initiator was synthesized, but still some of the initiator remains unreacted, illustrating that both steric hindrance and electrophilic balance affect the efficiency of the cationic ring-opening polymerization. All of the polymers were characterized in detail by using ¹H NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, and size exclusion chromatography to confirm the purity and distribution of the polymers.     

Silica gel‐Mediated Friedel‐Crafts Reaction of Indoles with Functionalized Nitroallylic Acetates via an SN1 Process

An environmentally friendly Friedel‐Crafts reaction was demonstrated between indoles and functionalized nitroallylic acetates in the presence of silica gel, providing the corresponding C‐3‐selective regioisomers in good to high overall chemical yields (70‐93%).