Amberlyst 15–Catalyzed Efficient Synthesis of 2,3‐Unsaturated Glycosides via Ferrier Rearrangement for Glycal

Amberlyst 15 serves as an inexpensive, effective, and environmentally friendly catalyst in converting 3,4,6‐tri‐O‐acetyl‐D‐glucal (1) into 2,3‐unsaturated O‐ and S‐glycosides via Ferrier rearrangement in moderate to excellent yields with high α selectivity.     

Ferric Sulphate Hydrate–Catalyzed,Microwave‐Assisted Synthesis of 2,3‐Unsaturated O‐Glycosides via the Ferrier Reaction

Fe₂(SO₄)₃ · xH₂O catalyzes the Ferrier reaction of per‐O‐acetylated/benzylated glycals with alcohols to give 2,3‐unsaturated α‐glycosides in a few minutes under microwave irradiation.     

Lithium Tetrafluoborate Catalyzed Ferrier Rearrangement — Facile Synthesis of Alkyl 2,3-Unsaturated Glycopyranosides

Treatment of tri-O acetyl-D-galactal 1 and tri-O-acetyl-D-glucal 2 with diverse alcohols in the presence of LiBF₄ in CH₃CN, furnished alkyl 2,3-unsaturated glycopyranosides 3-18 (50-86%).     

Microwave‐Enhanced Ferrier Reaction: A Facile Synthesis of 2,3‐Unsaturated‐O‐Glycosides Under Solvent‐Free Conditions

A variety of 2,3‐unsaturated‐O‐glycosides have been prepared by the Ferrier rearrangement of acetyl protected glycals under microwave irradiation using silica gel as an acid catalyst. Environmental friendliness, high yields, and short reaction times are the key features of this method. Furthermore, the method was applicable not only to the Ferrier reaction of 3,4,6‐tri‐O‐acetyl glucal and 3,4,6‐tri‐O‐acetyl galactal but also to the Ferrier reaction of 3,4‐di‐O‐acetyl arabinal.     

Synthesis and Characterization of Chlorobis(cyclopentadienyl) Titanium(IV) and Zirconium(IV) O,O’-Dialkyl and Alkylene Dithiophosphates

Abstract

Reactions of O,O′-dialkyl and alkylene dithiophosphoric acids with bis (cyclopentadienyl) titanium(IV) and zirconium (IV) dichloride in a 1:1 molar ratio in refluxing benzene proceeds with elimination of HCl and formation of the substituted derivatives, Cp₂MCl[S₂P(OR)₂] (where R = Et, Pr-n, Pr-i, Bu-i and Ph), Cp₂MCl[S₂POGO] (where G = ?CH₂CMe₂CH₂?, ?CH₂CEt₂CH₂? and ?CMe₂CMe₂?), (M = Ti and Zr). The complexes are dark red and yellow solids, soluble in common organic solvents and monomeric in nature. These have been characterized on the basis of elemental analyses, molecular weight determinations, IR, and NMR (¹H, ¹³C, and ³¹P).

GRAPHICAL ABSTRACT      

Zirconium(IV) Chloride Mediated Cyclodehydration of 1,2‐Diacylhydrazines: A Convenient Synthesis of 2,5‐Diaryl 1,3,4‐Oxadiazoles

Abstract

Zirconium(IV) chloride was invented as a mild catalyst for the cyclodehydration of 1,2‐diacylhydrazines. Efficient synthesis of several 2,5‐disubstituted 1,3,4‐oxadiazoles is reported.     

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.     

Aluminium Chloride–Catalyzed Claisen Rearrangement: Synthesis of Polyheterocycles Containing Oxygen,Nitrogen, and Sulfur

Synthesis of 1,8‐naphthyridine‐annulated polyheterocycles containing oxygen, nitrogen, and sulfur has been achieved by thionation and sequential Claisen rearrangement of 4‐(4′‐aryloxybut‐2′‐ynyloxy)‐1‐phenyl[1,8]‐naphthyridin‐2‐ones first by heating in 1,2‐dichlorobenzene for 1–2 h and then by anhydrous AlCl₃‐catalyzed Claisen rearrangement in dichloromethane for 1 h.     

Facile Synthesis of (S,S)‐1,2‐Diacylamides and (S,S)‐1,2‐Diamines with C 2‐Symmetry

A series of chiral vicinal tertiary diacylamides with C ₂‐symmetry was synthesized from (S)‐α‐phenylethylamine, different aromatic aldehydes, and oxalyl chloride. The diacylamides obtained were then reduced to afford chiral vicinal diamines with C ₂‐symmetry. We propose that the diacylamides existed in four stable conformational isomers in solution because of the dihedral angle between acylamide bonds.     

Zirconium Catalyzed Hydroaminoalkylation for the Synthesis of α-Arylated Amines and N-Heterocycles

The zirconium catalyzed hydroaminoalkylation of alkenes with N-aryl- and sterically demanding N-alkyl-α-arylated secondary amines by using commercially available Zr(NMe₂)₄ is reported. N-phenyl- and N-isopropylbenzylamine are used as amine substrates to establish the alkene substrate scope. Exclusively linear products are obtained in the presence of bulky vinylsilanes. Challenging α-heteroarylated amines and functionalized alkene substrates are compatible with this easy to use catalyst, affording a new disconnection strategy for the atom- and step-economic preparation of selectively substituted saturated α-arylated heterocycles.     

Application of Suzuki Cross‐Coupling Reaction Catalyzed by Ligandless Palladium Chloride in the Synthesis of Liquid Crystals

Palladium chloride–catalyzed Suzuki cross‐coupling reaction was applied to the preparation of highly pure multiring liquid crystals with a biphenyl unit. The optimal reaction condition is the combination of 0.5 mol% PdCl₂, pyridine, and K₃PO₄, which was able to catalyze the cross‐coupling of substituted aryl bromides with substituted trans‐cyclohexylphenylboronic acids to give pure products in 38–87% yields.     

Regioselective Hydroperoxygenation of Aralkanes and α,β‐Unsaturated Carbonyl Compounds Catalyzed by N‐Hydroxyphthalimide and 2,2′‐Azobis(4‐methoxy‐2,4‐dimethylvaleronitrile)

Abstract

Aerobic oxidation of aralkanes and α,β‐unsaturated carbonyl compounds in the presence of a catalytic amount of N‐hydroxyphthalimide (NHPI) and 2,2′‐Azobis(4‐methoxy‐2,4‐dimethylvaleronitrile) (V‐70) under 1 atmos. of oxygen at 30°C gave α‐hydroperoxyaralkanes and γ‐hydroperoxy‐α,β‐unsaturated carbonyl compounds, respectively.     

Synthesis of New 1,3‐bis(Heteroaryl)‐4,5‐imidazolidinediones Through Reaction of N,N′‐bis(Heteroaryl)methanediamines with Oxalyl Chloride

Reaction of N,N′‐bis(2‐pyridinyl, 3‐pyridinyl, 4‐pyridinyl, 2‐thiazolyl, 4‐nitrophenyl, and 2‐benzothiazolyl)methanediamines 1a–f with oxalyl chloride in dry dichloroethane in the presence of pyridine affords the corresponding 1,3‐bis (heteroaryl)‐4,5‐imidazolidinediones 3a–f in good to excellent yields. The essential role of pyridine in the reaction mixture is described, and reaction details as well as product characterization is discussed.     

Practical Synthesis of (S)‐(+)‐3‐Octanol by Lipase‐Catalyzed Enantioselective Acetylation

(S)‐(+)‐3‐Octanol (S)‐1 was prepared in high enantiomeric excess through catalyzed acetylation of racemic alcohol 1 by using lipase from Candida antarctica (Chirazyme L‐2) in the presence of vinyl acetate in toluene at 30°C. The pure (S)‐1 was obtained in 73% isolated yield with 62% conversion. Moreover, acetate (R)‐2 was converted to (S)‐1 via mesylation and followed by hydrolysis using sodium bicarbonate solution in 44% yield.     

Simple and Convenient One‐Pot Synthesis of Benzimidazoles and Benzoxazoles using N,N‐Dimethylchlorosulfitemethaniminium Chloride as Condensing Agent

N,N‐Dimethylchlorosulfitemethaniminium chloride (SOCl₂‐DMF) has been found to be an efficient reagent for the one‐pot synthesis of benzimidazoles and benzoxazoles in excellent yield by condensation of carboxylic acids with o‐phenylenediamine/2‐amino‐phenol.     

Novel Approach to the Synthesis of (R,S)‐Baclofen via PD(II)‐Bipyridine–Catalyzed Conjugative Addition

Synthesis of (R,S)‐baclofen is described starting from N‐phthalimidoacetaldehyde. The key step in the synthesis was Pd(II)‐bipyridine–catalyzed conjugative addition of 4‐chloroboronic acid.     

Synthesis and Crystal Structure of Bis(N,N''''- cyclohexyl-N''''''''-bis(trimethylsilyl)samarium Chloride

1INTRODUCTIONTheguanidinateanions,[(RN)2C(NR2?]-,canbeeasilymodifiedinbothelectronicdensityandstericbulkinessbyadjustingthesubstituents(RorR?onnitrogenatoms.Inthiscase,theyhavealrea-dybeenattractedmuchattentioninthecoordinationandorganometallicchemistry…     

Bismuth(III) Chloride–Catalyzed Three‐Component Coupling: Synthesis of α‐Amino Phosphonates

A simple and efficient method has been developed for the one‐pot synthesis of α‐amino phosphonates from the reaction of a carbonyl compound, amine, and dialkyl phosphite. The highly catalytic nature of bismuth(III) chloride and the fact that it is relatively nontoxic, low cost, easy to handle, and insensitive to small amounts of air and moisture make this method especially attractive for large‐scale synthesis.     

Synthesis of Fully Protected N‐Arylglycosylamines and Factors Affecting the Configuration of C1‐Substituents of N‐Arylglycosylamines

Abstract

An efficient method was reported for preparation of N‐arylglycosylamines in aqueous THF under reflux in good yields. The factors affecting the configuration of C₁‐substituents of N‐aryglycosylamines was investigated, that is, the influence of solvents, substituents of aromatic amines, and protecting groups of monosaccharides on the ratio of α‐ and β‐N‐arylglycosylamines.