Hypervalent Iodine in Synthesis XXXIV: Palladium-Catalyzed Coupling Reaction of o-Hydroxyarylaldehydes with Hypervalent Iodonium Salts Via Cleavage of the Aldehyde C-H Bond

A novel way of preparation for o-hydroxyarylketones with mild conditions and good yields by palladium-catalyzed coupling reaction of o-hydroxyarylaldehydes with hypervalent iodonium salts via the cleavage of the aldehyde C-H bond has been reported.     

One‐Pot Synthesis of 2‐Arylthio‐2‐cyclohexenone Derivatives by the Diels–Alder Reaction of 4‐Arylthio‐3‐hydroxy‐2‐pyrones

The base‐catalyzed Diels–Alder reactions of 4‐arylthio‐3‐hydroxy‐2‐pyrones are reported. Treatment of 4‐arylthio‐3‐hydroxy‐2‐pyrones and dienophiles with triethylamine gave 2‐arylthio‐2‐cyclohexenone derivatives by the Diels–Alder reaction involving a decarboxylation in excellent to reasonable yields.     

Mild and Highly Efficient Stereoselective Synthesis of 2,3‐Unsaturated Glycopyranosides using La(NO3)3 · 6H2O as a Catalyst: Ferrier Rearrangement

A mild and highly efficient stereoselective reaction of 3,4,6‐tri‐O‐acetyl‐d‐glucal with a variety of nucleophiles, viz. alcohols, phenols, thiols, thiophenols, and allyl trimethyl silane (TMS), in the presence of 5 mol% of lanthanum(III) nitrate hexahydrate under solvent‐free conditions yielded the corresponding 2,3‐unsaturated glycopyranosides (pseudoglycals) in excellent yields.     

From Levulinic Acid to Biheterocycles: Synthesis of 1-[(5-Hydroxy-5-trifluoromethyl-3-substituted-4,5-dihydro-1H-pyrazol-1-yl)-3-(5-trifluoromethyl-1H-pyrazol-3-yl)propan-1-ones

We develop an efficient method to synthesize novel propionyl-spaced bisheterocyclic compounds. It entails cyclocondensation of 3-(5-trifluoromethyl-1H-pyrazol-3-yl)propanoyl hydrazide obtained from levulinic acid, with 1,1,1-trifluoro-4-methoxy-3-alken-2-ones proceeding regiospecifically to 1-[(5-trifluoromethyl-5-hydroxy-3-substituted-4,5-dihydro-1H-pyrazol-1-yl)-3-(5-trifluoromethyl-1H-pyrazol-3-yl)propan-1-one derivatives.     

Synthesis of New N‐(5‐Oxo‐2,5‐dihydro)pyrrol‐3‐yl Glycines and N‐(5‐Oxo‐2,5‐dihydro)pyrrol‐3‐yl Glycines Esters

Following our efforts towards the synthesis of new potential inhibitors of Xanthine Dehydrogenase (XDH), we describe here a general method for the preparation of N-(5-oxo-2,5-dihydro)pyrrol-3-yl glycines and N-(5-oxo-2,5-dihydro)pyrrol-3-yl glycine esters from glycine ethyl ester hydrochloride and various 4-hydroxy-5-oxo-2,5-dihydro-1H-pyrrole-3-carboxylic acid esters and carbonitriles.     

Highly Efficient and Selective Deprotection Method for Prenyl,Geranyl, and Phytyl Ethers and Esters Using Borontrifluoride–Etherate

An efficient, simple, and practical method has been developed for the deprotection of prenyl, geranyl, and phytyl ethers and esters of aromatic and aliphatic compounds using borontrifluoride–etherate (BF₃ · OEt₂) at room temperature in good to excellent yields for the first time.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Synthesis and Electrophilic Cyclization Reactions of Diphenyl 3-Methylpenta-1,2,4-trienyl Phosphine Oxide

Diphenyl 3-methyl-penta-1,2,4-trienyl phosphine oxide can be readily prepared via an atom-economical [2,3]-sigmatropic rearrangement of the mediated alkenynyl phosphinite formed in situ by reaction of 3-methylpent-1-en-4-yn-3-ol with diphenylchlorophosphine. Electrophilic cyclization reactions of the vinylallenyl phosphine oxide prepared were investigated as it was established that the reactions proceeded with formation of various heterocyclic or highly unsaturated compounds with participation of the allenic and/or 1,3-dienic part of the vinylallenic system with neighboring group participation of phosphoryl and/or vinylic group.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

CeCl3·7H2O-Catalyzed Synthesis of 1-Oxo-hexahydroxanthene Derivatives in Aqueous Media

Cerium(III) chloride heptahydrate (CeCl₃·7H₂O) catalyzes the reaction of substituted salicylaldehydes with 1,3-cyclohexane dione or dimedone in aqueous medium at reflux temperature to afford the corresponding 1-oxo-1,2,3,4,9,10-hexahydroxanthene derivatives4 0 in high yields.     

Simple and Efficient Procedure for the Friedel–Crafts Acylation of Aromatic Compounds with Carboxylic Acids in the Presence of P2O5/AL2O3 Under Heterogeneous Conditions

An efficient and chemoselective method for the Friedel–Crafts acylation of aromatic compounds using P₂O₅/Al₂O₃ and carboxylic acids. Both aromatic and aliphatic carboxylic acids reacted easily to afford the corresponding aromatic ketones in good yields.     

Copper-Catalyzed Cyanopropylation of Activated Alkenes

A practical copper-catalyzed alkylarylation of activated alkenes with azobisisobutyronitrile (AIBN) and beyond has been developed, in which incorporation of 3^o nitrile moiety into an oxindole scaffold proceeded smoothly through cascade radical addition/C(sp²)-H cyclization. The use of readily available AIBN as radical source and inexpensive CuI as catalyst, as well as broad substrate scope and the simplicity of operation and handling, make this protocol a highly attractive approach to oxindoles bearing 3^o nitrile moiety.