An improved synthesis of pyrroles from N-p-toluenesulfonylglycine esters and α,β-unsaturated aldehydes and ketones

N-p-Toluenesulfonylglycine esters 2 condensed with α,β-unsaturated carbonyl compounds 1 in the presence of the non-nucleophilic base DBU to give hydroxypyrrolidines 3 . Dehydration with phosphorus oxychloride-pyridine, followed by DBU mediated elimination of p-toluenesulfinic acid, gave a series of synthetically useful pyrrole-2-carboxylates 5 .     

An efficient synthesis of α,β-unsaturated aldehydes by a four-carbon unit extension of Grignard reagents

Copper-catalyzed addition of organomagnesium halides to 2-(2,2-diethoxyethyl)oxirane ( 1 ) affords aldol acetals 2 which upon acid treatment undergo hydrolysis and dehydration to give α,β-unsaturated aldehydes 7 with high yields.     

Enantioselective synthesis of β,β-dialkyl α-hydroxy γ-butyrolactones

An ephedrine-derived morpholine dione is employed in the synthesis of chiral alkylidene morpholinones that are efficiently converted to β-substituted α,γ-dihydroxy butyramides, precursors of the corresponding butyrolactones. Enantioselective synthesis of a spiro analog of pantolactone as well as a naturally occurring pantolactone homolog is achieved with this protocol.     

An efficient synthesis of substituted alkyl acrylates using α-keto amides

The addition of α-keto amides as a NH-acid to alkyl propiolates and dialkyl acetylenedicarboxylates in the presence of a catalytic amount of triphenylphosphine gives the corresponding substituted alkyl acrylates.     

A facile and efficient synthesis of diethyl α,α‐chlorofluoroalkanephosphonates

A facile and efficient synthetic methodo‐ logy for the preparation of diethyl α,α‐chlorofluoro‐ alkanephosphonates is described. A wide variety of diethyl α‐hydroxyphosphonates were investigated by a two‐step halogenation procedure, which includes nucleophilic chlorination with PPh₃ and CCl₄ and electrophilic fluorination with N‐fluorobisbenzene‐ sulfonimide. Aromatic and aliphatic α,α‐chlorofluoro‐ phosphonates could be prepared by this method with acceptable yields. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:250–255, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20604     

An intermediate in a new synthesis approach to β‐substituted β‐hydroxy­aspartame

The crystal and molecular structure of 1‐tert‐butyl 4‐ethyl (2′R,3′R,5′R,2S,3S)‐3‐bromo­methyl‐3‐hydroxy‐2‐[(2′‐hydroxy‐2′,6′,6′‐tri­methyl­bi­cyclo­[3.1.1]­hept‐3′‐yl­idene)­amino]­succinate, C₂₁H₃₄BrNO₆, is presented. This compound is an intermediate in the new synthetic route to β‐substituted β‐hydroxy­aspartates, which are blockers of glutamate transport.     

An efficient new enzymatic method for the preparation of β-aryl-β-amino acid enantiomers

An efficient synthesis of β-aryl-β-amino acid enantiomers has been developed via the lipase-catalysed enantioselective hydrolysis of the corresponding racemic ethyl esters in an organic solvent. High enantioselectivities (E >100) were observed when the lipase PS-catalysed reactions were performed with H₂O (0.5 equiv) in diisopropyl ether at 45 °C. The products could be easily separated and were obtained in good yields of 40%.     

An improved procedure for the preparation of 9-β-D-Arabitiofuranosyl-2-ñuoroadenine

An improved procedure for the preparation of 9-β-D -arabinofuranosyl-2-fluoroadenitie (11) utilizing the readily available 2,4,5,6-tetraaminopyrimidine (1) is described; the overall yield based on the arabinosugar was quadrupled.     

An improved procedure for the synthesis of 2-methoxyisobutylisonitrile: An efficient complexing agent for99mTc

^99mTc hexakis (2-methoxyisobutylisonitrile) is a cationic complex useful as a myocardial perfusion agent. The synthesis of 2-methoxyisobutylisonitrile (MIBI) by a modified and improved procedure in a two-step process with an overall yield of 53% is described. The preparation of its copper and technetium-99m complexes is also presented.     

The synthesis of β-heteroarylamino-α,β-dehydro-α-amino acid and β-heteroarylamino-α-amino acid derivatives

From heteroarylaminomethyleneoxazolones 4 , obtained from N-heteroarylformamidines 2 and 2-phenyl-5-oxo-4,5-dihydro-1,3-oxazole ( 3 ), the following β-heteroarylamino-α,β-dehydro-α-amino acid derivatives were prepared: methyl 8 and ethyl esters 9 , amides 10 and 11 , hydrazides 12 , and azides 15 . By catalytic hydrogenation the compounds 4 were converted into β-heteroarylamino substituted amides 18 and β-heteroarylamino-α-amino acids 20 .     

Lanthanum immobilized on chitosan: a highly efficient heterogeneous catalyst for facile synthesis of novel (α,β‐unsaturated) β‐aminoketones

A new heterogeneous catalyst, lanthanum immobilized on chitosan, was synthesized and used for the aza‐Michael reaction of β‐enaminone under microwave irradiation. The characteristic structural features of the catalyst were determined using Fourier transform infrared spectroscopy, powder X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, transmission and scanning electron microscopies and inductively coupled plasma atomic emission spectroscopy. The stability of the catalyst was evaluated using thermogravimetric analysis. The use of recyclable catalyst and glycerol as solvent makes this procedure environmentally benign and economically viable. Copyright © 2016 John Wiley & Sons, Ltd.     

An improved procedure for the synthesis of 2-morpholinoethanamine

2-Morpholinoethanamine is prepared rapidly mainly in aqueous conditions from inexpensive and commercially accessible starting materials. The process development of an effective synthetic route by utilizing morpholine as the starting material via Michael addition, hydrazinolysis, and Curtius rearrangements was undertaken. The optimal conditions were selected in the experiments. The total yield was 81.8% and it was a convenient process.     

β-lithiations of carboxamides. Synthesis of β-substituted-α,β-unsaturated amides

N-Methyl-2-methyl-3-(benzotriazol-l-yl)propanamide, on treatment with butyllithium forms a dianion which on treatment with alkyl and benzyl halides, aldehydes and ketones affords monosubstituted products; with ethyl p-toluate, a lactam is formed. The alkylated derivatives eliminate benzotriazole in the presence of base to afford trisubstituted α,β-unsaturated amides.     

An efficient one‐pot synthesis of 2‐benzylpyrroles and 3‐benzylindoles

One‐pot regioselective benzylation of pyrroles and indoles using zirconium tetrachloride is discussed. This has been achieved by in‐situ generation of di(1H‐pyrrol‐1‐yl)zirconium(IV) chloride and di(1H‐indol‐1‐yl)zirconium(IV) chloride. It was observed that benzylation reactions of these complexes using n‐BuLi occurred at C‐2 position for pyrrole and C‐3 for indole. Copyright © 2011 John Wiley & Sons, Ltd.     

A new approach to the synthesis of 2β- and 3β-hydroxygibberellins

The first examples of the use of hydroxyl inversion reactions to prepare the gibberellin plant hormones are described. Treatment of 2- and 3-mesylates with caesium acetate gave, after hydrolysis, good yields of the required 2β- and 3β-hydroxygibberellins. Alternatively inversion of the 2-mesylate and hydrolysis of the 7-methyl ester may be achieved in one-pot by treatment of (2) with potassium superoxide.     

Transformations of isomeric naphthopyranones. The synthesis of substituted β-naphthyl-α,β-dehydro-α-amino acid derivatives

The opening of the pyranone ring in 2H-naphtho[1,2-b]pyran-2-one derivative (1) and 3H-naphtho[2,1-b]-pyran-3-one derivatives 8 and 20 with nucleophiles afforded 3-(naphthyl-1)- and 3-(naphthyl-2)propenoates (substituted β-naphthyl-α,β-dehydro-α-amino acid derivatives) 7, 13, 14, 15, 24 , and 35 .     

One-step stereospecific synthesis of α,β-dehydroamino acids and dehydropeptides.

Dehydroamino acids and dehydropeptides were prepared by a one-pot reaction employing diethyl chloroposphate in the presence of sodium hydride. The reaction is stereospecific and proceeds without racemization.     

The synthesis of β-heteroarylamino-α,β-dehydro-α-amino acid derivatives via thiazolones

2-Alkoxy-4-heteroarylaminomethylene-5(4H)-thiazolones 4 were converted with various nucleophiles into β-heteroarylamino-α,β-dehydro-α-amino acid derivatives 11, 14, 15, 16, 17, 18 , and 19 . Reduction of 4 with sodium borohydride in ethanol saturated with gaseous ammonia afforded the corresponding β-heteroaryl-amino substituted alanyl amides 20 . Thiazoledione derivative 7a was transformed with sodium methoxide in methanol into 1-(4,6-dimethylpyrimidinyl-2)-4-mercaptocarbonylimidazol-2(3H)-one ( 8a ).     

Regioselective synthesis of 3-hydroxyisoxazoles and 5-isoxazolones from β-amino α,β-unsaturated esters

The regioselective synthesis of 3-hydroxyisoxazoles and 5-isoxazolones is accomplished by the reaction of β-amino α,β-unsaturated esters with hydroxylamine hydrochloride in the presence of appropriate bases. The total yield of isoxazole derivatives is sensitively influenced on the β-substituent group of the esters.     

A novel synthesis of α,β-unsaturated phosphonates

A stereoselective synthesis of α,β-unsaturated phosphonates based on the reaction of S-(β-oxoalkyl)-dithiophosphates and Se-(β-oxoalkyl)selenophosphates with sodium dialkyl phosphites is described.