Resolution of 1-substituted-3-methyl-3-phospholene 1-oxides by molecular complex formation with TADDOL derivatives

The antipodes of 1-aryl-, 1-alkyl- and 1-alkoxy-3-methyl-3-phospholene 1-oxides 1a–h and 1-phenyl-3-methyl-3-phospholene 1-sulfide 1i were separated in good yields and high enantiomeric excesses (up to >99% ee) by resolution via formation of diastereomeric complexes with either (−)-(4R,5R)-4,5-bis(diphenylhydroxymethyl)-2,2-dimethyldioxolane 2 (TADDOL) or (−)-(2R,3R)-,,′,′-tetraphenyl-1,4-dioxaspiro[4.5]decan-2,3-dimethanol 3. The stereostructure of the supramolecular formations and the absolute configurations of the 3-phospholene oxides 1a, 1e and 1f were elucidated by single crystal X-ray crystallography. CD spectroscopy was also useful in determining the absolute configurations of some phospholene oxides 1b, 1c, 1g and 1h.     

Dynamic kinetic resolution of 1-substituted-3-methyl-3-phospholene oxides via the formation of diastereomeric alkoxyphospholenium salts

A dynamic kinetic resolution method based on the formation of covalent diastereomeric intermediates was elaborated for the preparation of enantiomerically enriched 1-substituted-3-methyl-3-phospholene oxides. The 3-phospholene oxides were first converted to the corresponding chloro-3-phospholenium chlorides. The dynamic interconversion between the enantiomers of the chlorophospholenium salts was verified experimentally, as it is the key step for a dynamic resolution. The cyclic chlorophospholenium salts were reacted with a chiral auxiliary bearing a hydroxy function to form the corresponding diastereomeric alkoxyphospholenium salts in unequal amounts. The diastereomeric species then rearranged into the corresponding optically active 3-phospholene oxides upon heating. After a screening of chiral auxiliaries and the optimization of the reaction conditions, several scalemic 1-aryl- or 1-alkyl-3-methyl-3-phospholene oxides were prepared in excellent yields and with ee-s up to 35%. The key steps of this resolution were investigated by quantum chemical calculations to get some insights into the factors responsible for the stereoselection.     

Reactions of 2-phospholene 1-oxides with bromine in some media: Facile preparation of bromohydrin derivatives of 2-phospholenes

Reactions of 1-phenyl- and 1-methoxy-2-phospholene 1-oxides with bromine in aqueous organic solvents or in a protic medium, such as methanol, easily afforded the corresponding 2-bromo-3-hydroxy- or 2-bromo-3-methoxyphospholane 1-oxide derivatives. The reaction mechanism was postulated based on the stereochemistry of the products.     

Selective reduction of 1,4-diarylimidazoline-3-oxides to imidazolidin-1-ols and hydroxylamine derivatives

Abstract  

C-2-unsubstituted imidazoline-3-oxides were reduced with NaBH₄ in THF to give the corresponding trans-3,5-diarylimidazolidin-1-ols, while under the same conditions C-2-substituted derivatives gave the corresponding ring–chain–ring tautomers. Treatment of the crude reaction mixture from the reduction of C-2-unsubstituted imidazoline-3-oxides with a MeOH–H₂O mixture provided reductive C–N bond cleavage to give hydroxylamines, while under the same conditions ring–chain–ring tautomers remained unchanged.     

1-Methyl-3-piperidone and 1-methyl-3-pyrrolidone derivatives from a dieckmann reaction

Attempts to prepare 1-methyl-5-carbethoxy-3-piperidone by a Dieckmann cyclization led to formation of its diethyl ketal on workup. The five-membered ring system, 1-methyl-4-(ethoxy-carbonylmethyl)-3-pyrrolidone was also formed in the cyclization.     

On the mechanism of formation of 1,1-dimethylpyrazolin-3-oxides

Conclusions The primary product during the acylation of N,N-dimethylhydrazine with anhydrides of,-unsaturated acids is the N,N-dimethylhydrazide of the acid, which at elevated temperatures rearranges to its tautomer — the corresponding 1,1-dimethylpyrazolin-3-oxide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 917–918, April, 1970.`     

Reaction of sterically hindered 1-hydroxy-3-imidazoline 3-oxides with phenyllithium

The reaction of 3-imidazoline 3-oxide derivatives with phenyllithium followed by oxidation affords nitroxyl radicals of the 2-imidazoline or 2-imidazoline 3-oxide series depending on the nature of the substituent in position 2 of the heterocycle.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 292–294, February, 1994.     

Reactions of some 1,2-oxa-4-phospholene derivatives with alcohols and amines

The reactions of P-alkyl and P-alkoxy derivatives of oxaphospholene with diethylamine and of oxaphospholene P-amide with alcohol proceed in a complex manner and included phosphorylation, alkylation, and salt formation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1329–1332, October, 1971.