Regio- and stereoselective microwave-assisted synthesis of 5-alkyl-4-alkenyl-4-phenyl-1,3-oxazolidin-2-ones

Chiral symmetrical alk-2-yne-1,4-diols have been stereoselectively transformed into 5-alkyl-4-alkenyl-4-phenyl-1,3-oxazolidin-2-ones, which are precursors of quaternary α-amino β-hydroxy acids. The key step was the cyclization of the bis(tosylcarbamates) of 2-phenylalk-2-yne-1,4-diols, easily obtained from the starting chiral diols. These cyclizations were accomplished with complete regioselectivity and up to 92:8 dr in the presence of catalytic amounts of Ni(0) or Pd (II) derivatives under microwave heating.     

Mass spectral fragmentation pattern of 2,3-dimethyl- and 2-methyl-3-phenyl-4-arylazoisoxazol-5-ones

2,3-Dimethyl-4-arylazoisoxazol-5-ones and 2-methyl-3-phenyl-4-aryiazoisoxazol-5-ones undergo considerable fragmentation on electron impact. The base peaks in the mass spectra are at mass 56 and 118 respectively attributed to the N-methylacetonitrile cation and the N-methylbenzonitrile cation.     

A stereochemical investigation of 2-methyl- and 2,5-dimethyl-3-phenyl-1,3-oxazolidines using NMR

The stereochemical properties of two 2-methyl-3-phenyl-1,3-oxazolidines and two of its 5-methyl substituted and four of its 2,5-dimethyl substituted derivatives have been investigated by pmr and cmr methods. The compounds of 2,5-dimethyl-3-phenyl-1,3-oxazolidines exist in isomeric cis and trans forms at the two methyl groups on the heterocyclic ring.     

Mass spectral fragmentation pattern of 3-methyl- and 3-phenyl-4-(N-methylarylhydrazono)isoxazol-5-ones

3-Methyl-4-(N-methylarylhydrazono)isoxazol-5-ones and 3-phenyl-4-(N-methylarylhydrazono)isoxazol-5-ones undergo considerable fragmentation on electron impact involving rupture of the isoxazolone ring and bonds in the N-methylarylhydrazono side chain.     

Synthesis of new chiral N-arylsulfonyl-1,3-oxazolidin-2-ones from α-amino acids

A variety of new chiral N-arylsulfonyl-1,3-oxazolidin-2-ones were prepared in three steps starting from (d)- and (l)-amino acid. N-Arylsulfonyl amino alcohols, derived from amino acids, were carbonylated with the bis-(trichloromethyl) carbonate (BTC), in the presence of triethylamine, to provide optically pure N-phenylsulfonyloxazolidin-2-ones 3a–f, N-naphthylsulfonyloxazolidin-2-ones 3g–j and N-tosylsulfonyloxazolidin-2-ones 3k–p in good yields.     

Synthesis and Diels-Alder reactions of 2-alkyl-5-methylene-1,3-dioxolan-4-ones and 2-alkyl-3-acyl-5-methylene-1,3-oxazolidin-4-ones: Highly exo and diastereoface selective chiral ketene equivalents

Chiral dienophiles 1–3 undergo highly exo and diastereoface selective Diels-Alder reactions. The Diels-Alder reactions of 3 are also highly exo selective under Lewis acid catalyzed conditions.     

Synthesis of novel 2-phenyl-5-substituted dihydropyrimidines using 2-phenyl-1,3-diaza-1,3-butadienes and electron-deficient olefins

A novel synthetic method for 2,5-disubstituted dihydropyrimidines was developed. The cyclization of 1,3-diaza-4-dimethylamino-1,3-butadienes having a N-protecting group (N-Boc, N-Cbz, N-n-C₄H₉, N-Bn or N-Ph) with electron-deficient olefins, such as α,β-unsaturated carbonyl compounds, phenyl vinyl sulfone, and acrylonitrile was studied in detail. The cyclization smoothly proceeded to afford 4-dimethylamino-1,4,5,6-tetrahydropyrimidines or 1,6-dihydropyrimidines in good yields. The isolated 4-dimethylamino-1,4,5,6-tetrahydropyrimidines were converted to 2,5-disubstituted-1,6-dihydropyrimidines through the β-elimination of the dimethylamino group. 2,5-Disubstituted-1,4(6)-dihydropyrimidines were obtained after removal of the N-Boc or N-Cbz group. Independent tautomers of the resulting dihydropyrimidines were observed.     

Electrochemically promoted C-N bond formation from acetylenic amines and CO2. Synthesis of 5-methylene-1,3-oxazolidin-2-ones

[reaction: see text] An efficient electrochemical synthesis of 5-methylene-1,3-oxazolidin-2-ones (2a-h) from acetylenic amines (1a-h) and carbon dioxide has been achieved by direct electrolysis of solution of MeCN and Et4NPF6 containing the amine, with subsequent CO2 bubbling and heating. The yields vary from good to excellent, the conditions are mild, and the use of toxic and harmful chemicals and catalysts is avoided.     

Methylation of 3-methyl- and 3-phenyl-4-arylhydrazonoisoxazol-5-ones with diazomethane

3-Methyl(or phenyl)-4-arylhydrazonoisoxazol-5-ones on methylation with diazomethane afford 3-methyl(or phenyl)-4-(N-methylarylhydrazono)isoxazol-5-ones and 3-methyl(or phenyl)-5-methoxy-4-arylazoisoxazoles. The latter compounds readily rearrange to 4-methoxycarbonyl-5-methyl(or phenyl)-2-aryl-2H-1,2,3-triazoles.     

A convenient synthesis of 1,3-oxazolidin-4-ones and 1,3-oxazin-4-ones

1,3-Oxazolidin-4-ones and 1,3-oxazin-4-ones were synthesized by formal cyclocondensation of imines with α- or β-hydroxy acids.     

Synthesis of 1,4-dihydro-4-methyl-1-phenyl-5H-1,3,4-benzotriazepin-5-ones

The synthesis of 1,4-dihydro-4-methyl-1-phenyl-5H-1,3,4-benzotriazepin-5-one ( 4a ) and its 8-chloro analog ( 4b ) is described. Attempted synthesis of the 2-methyl analog of 4a from 2-(phenylamino)benzoic acid 1-methylhydrazide ( 10 ) and triethyl orthoaeetate led only to the Schiff base intermediate, 2-(phenylamino)benzoic acid 2-(1-ethoxyethylidene)-1-methylhydrazide ( 11 ). Cyclization of 11 was attempted unsuccessfully with a variety of reagents. The intere?ting reaction products from the treatment of 11 with trifluoroacetic acid are described.     

5-Acyl-4-amino-2-phenyl-1,3-oxazin-6-ones

Intramolecular cyclization of acyl(ethoxycarbonyl)keteneN-benzoylaminals in boiling Ph₂O gives 5-acyl-4-amino-2-phenyl-1,3-oxazin-6-ones.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1322–1323, July, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grant No. 94-03-08964).     

Synthesis and spectral behavior of 6-phenyl-5,6,7,8-tetrahydro-4H-1,3,6-dioxazocines using NMR

Heterocyclic compounds of four 6-phenyl-5,6,7,8-tetrahydro-4H-1,3,6-dioxazocines have been synthesized by condensation of the corresponding N,N-bis(2-hydroxyethyl)- or N,N-bis(2-hydroxypropyl)anilines with aldehyde or ketone in the presence of acid. The pmr and cmr spectra of these compounds were recorded to determine their stereochemical structures. On the basis of the chemical shifts due to the γ-effects, the stereochemical structures are discussed.     

Mass spectral fragmentation pattern of 3-methyl-4-arylaminomethyleneisoxazol-5-ones

The mass spectral fragmentation patterns of 3-methyl-4-arylaminomethyleneisoxazol-5-ones obtained by electron impact have been elucidated. The base peaks are due to the molecular ions. The main fragmentation routes involve loss of H, OH, H₂O, CO₂ and COOH from the molecular ions as well as rupture of the exocyclic CH-NH bond.     

NMR parameters,isomerism, and conformational analysis of 3-methyl-2-phenyl-5-(3-methyl-2-phenyl-3,4-dehydropiperid-6-yl)-pyridine

The configurational and conformational features of the trans and cis isomers of 3-methyl-2-phenyl-5-(3-methyl-2-phenyl-3,4-dehydropiperid-6-yl)pyridine, formed as by-products in the phenylation of -picoline by phenyllithium, were established. The revealed stereospecificity of the ⁵J_HH and ¹J_CH SSCCs may be utilized as an independent criterion in the conformational analysis of piperideine systems.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 71–74, January, 1993.     

Synthesis and spectral properties of 3-(2-aryl-5-methyl-1,3-oxazol- 4-yl)-2-(2,5-dimethylthiophen-3-yl)cyclopent-2-en-1-ones

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Stereoselective Diels–Alder reactions of 3-phosphonopropenoyl derivatives of 1,3-oxazolidin-2-ones

Dienophiles of the general structure (EtO)₂P(O)CHCHCOX have been prepared, where X represents an oxazolidinone chiral auxiliary. Use of the (S)-4-isopropyl-5,5-diphenyl-1,3-oxazolidin-2-one auxiliary gave Diels–Alder adducts with several cyclic and acyclic dienes. The crystal structures of the main cyclohexa-1,3-diene and 2,3-dimethylbutadiene adducts formed during reactions in the presence of dialkylaluminium halides are consistent with a reaction, which is stereoselectively endo with respect to the carbonyl group and occurs on the less hindered face of the dienophile when aluminium is chelated between the two carbonyl groups.