A one-pot synthesis of tetrahydroisoquinolin-4-ols via a novel acid-catalyzed rearrangement of 5-aryloxazolidines

Benzaldehydes with electron-donating substituents react smoothly with a nonstabilized azomethine ylide derived from sarcosine and formaldehyde to form 5-aryloxazolidines as intermediates, which undergo rearrangement into 2-methyl-1,2,3,4-tetrahydroisoquinolin-4-ols in high yields by simple heating with hydrochloric acid. This one-pot synthesis of tetrahydroisoquinolines can be considered as a formal [3+3] cycloaddition of the azomethine ylide to the aromatic aldehyde. © 2013 Elsevier Ltd. All rights reserved

A simple two-step synthesis of 2-(alkylamino)-1-arylethanols, including racemic adrenaline, from aromatic aldehydes via 5-aryloxazolidines

Benzaldehydes react smoothly with nonstabilized azomethine ylides, generated in situ from sarcosine/formaldehyde or N-(methoxymethyl)-N- (trimethylsilylmethyl)benzylamine, to give 5-aryloxazolidines as intermediates. These were converted into 2-(alkylamino)-1-arylethanols in good yields by simple heating in methanol with hydrochloric acid, or by treatment with hydrazine hydrate in ethanol. © 2013 Elsevier Ltd. All rights reserved

Reaction of 5-aryloxazolidines with arylmagnesium bromides as a new route to N-benzyl-β-hydroxyphenethylamines as starting materials for the preparation of 4-aryl-1,2,3,4-tetrahydroisoquinolines

Benzaldehydes react smoothly with the non-stabilized azomethine ylide derived from sarcosine and formaldehyde to form 5-aryloxazolidines as intermediates, which undergo ring-opening to give N-benzyl-β- hydroxyphenethylamines in good yields by the action of arylmagnesium bromides. Their subsequent acid-catalyzed cyclization into 4-aryl-1,2,3,4- tetrahydroisoquinolines was performed in moderate to good yields. © 2013 Elsevier Ltd. All rights reserved

Domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylalkylidene)malononitriles: Synthesis of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans and a rare case of [1,5] sigmatropic shift of the nitro group

A variety of functionalized 6-(trifluoromethyl)-6H-dibenzo[b,d]pyrans were easily synthesized in good yields under mild conditions by a domino reaction of 3-nitro-2-(trifluoromethyl)-2H-chromenes with 2-(1-phenylethylidene)- and 2-(1-phenylpropylidene)malononitriles. In the latter case, intermediate 7-amino-10-methyl-10-nitro-9-phenyl-6-(trifluoromethyl)-10,10a-dihydro-6H- benzo[c]chromene-8-carbonitriles were isolated as a result of a rare [1,5] sigmatropic shift of the nitro group. © 2013 Elsevier Ltd. All rights reserved

Synthesis of β-(trifluoromethyl)furans and spiro-gem- dichlorocyclopropanes from cyclic 1,3-dicarbonyl compounds and α-(trihaloethylidene)nitroethanes

While 1,3-dicarbonyl compounds react with (E)-1,1,1-trifluoro-3-nitrobut-2- ene in the presence of sodium acetate to produce the target β- (trifluoromethyl)furans, their reaction with (E)-1,1,1-trichloro-3-nitrobut-2- ene, under the same conditions, took an entirely different course and gave spiro-gem-dichlorocyclopropanes bearing a 1-nitroethyl moiety, with high diastereoselectivity and in good yields. © 2013 Elsevier Ltd. All rights reserved

Synthesis of 5-(trifluoromethyl)-5H-chromeno[3,4-b]pyridines from 3-nitro-2-(trifluoromethyl)-2H-chromenes and aminoenones derived from acetylacetone and cyclic amines

Reactions of 3-nitro-2H-chromenes with aminoenones derived from acetylacetone and cyclic amines proceed diastereoselectively to give functionalized 2,3,4-trisubstituted chromanes as a result of nucleophilic addition of the vinylogous β-methyl group at the C-4 atom of the chromene system. From these compounds, under acidic conditions, 5-(trifluoromethyl)-5H- chromeno[3,4-b]pyridines and 4-acetoacetonyl-3-nitro-2-(trichloromethyl/phenyl) chromanes, depending on the substituent at the 2-position, were obtained in moderate to good yields. © 2013 Elsevier Ltd. All rights reserved

Synthesis and Reactivity of Electron-Deficient 3-Vinylchromones

The reported methods and data for the synthesis and reactivity of electron-deficient 3-vinylchromones containing electron-withdrawing groups at the exo -cyclic double bond are summarized and systematized for the first time. The main methods for obtaining these compounds are Knoevenagel condensation, Wittig reaction, and palladium-catalyzed cross-couplings. The most important chemical properties are transformations under the action of mono- and dinucleophiles, ambiphilic cyclizations, and cycloaddition reactions. The cross-conjugated and polyelectrophilic dienone system in 3-vinylchromones provides their high reactivity and makes these compounds valuable building blocks for the preparation of more complex heterocyclic systems. Chemical transformations of 3-vinylchromones usually begin with an attack of the C-2 atom and are accompanied by the opening of the pyrone ring followed by recyclization, in which the carbonyl group of chromone, an exo -double bond or a substituent on it can take part. The mechanisms of the reactions are discussed, the conditions for their implementation are described, and the yields of the resulting products are given. This review focuses on an analysis and generalization of the knowledge that has accumulated on the chemistry of electron-deficient 3-vinylchromones, mostly over the past 15 years. 1 Introduction 2 Synthesis of 3-Vinylchromones 3 Reactions with Mononucleophiles 4 Reactions with Dinucleophiles 5 Ambiphilic Cyclization 6 Cycloaddition Reactions 7 Other Reactions 8 Conclusion. © 2021 BMJ Publishing Group. All rights reserved.The Russian Science Foundation (project No. 18-13-00186) is acknowledged for funding

Synthesis of benzopyranopyrrolidines via 1,3-dipolar cycloaddition of nonstabilized azomethine ylides with 3-substituted coumarins

A three-component reaction of 3-substituted coumarins with N-alkyl-α-amino acids and aldehydes gave 1-benzopyrano[3,4-c]pyrrolidines as a result of a 1,3-dipolar cycloaddition of an intermediate nonstabilized azomethine ylide at the double bond of the coumarin system in moderate to good yields. In most cases, high regio- and stereo-selectivity of the [3+2] cycloaddition was observed. © 2013 Elsevier Ltd. All rights reserved

An improved synthesis and some reactions of diethyl 4-oxo-4H-pyran-2,5- dicarboxylate

The reaction of ethyl 2-(dimethylamino)methylene-3-oxobutanoate with diethyl oxalate in the presence of sodium hydride in THF gave diethyl 4-oxo-4H-pyran-2,5-dicarboxylate, from which 4-oxo-4H-pyran-2,5-dicarboxylic and 4-oxo-1-phenyl-1,4-dihydropyridine-2,5-dicarboxylic acids and their derivatives were obtained in good yields. © 2013 Elsevier Ltd. All rights reserved

Highly regio-and stereoselective addition of ethyl 3-aminobut-2-enoates to 2-substituted 3-nitro-2H-chromenes

Ethyl 3-aminobut-2-enoates MeC(NHR)=CHCO2Et (R = H, Me, Bn) whose reaction site is C(2) atom add to 2-R-3-nitro-2H-chromenes at their C(4) atom to give the corresponding trans,trans-2,3,4-trisubstituted chromanes. Analogous substrates MeC(NR2)=CHCO2Et (NR2 is piperidin-1-yl or morpholin-4-yl) react by their C(4) methyl group to afford cis,trans-2,3,4-trisubstituted chromanes. The stereochemistry of the products was established by X-ray diffraction analysis. © 2013 Mendeleev Communications. All rights reserved