Studies on the reactivity of 23E-benzylidene spirostanes (original) (raw)

An Assisted Solvolysis of 23-Spirostanyl Bromides and Tosylates. A New Rearrangement of Spirostanes to the Bisfuran Systems

The Journal of Organic Chemistry, 2002

Steroidal sapogenins bearing a good leaving group at C23 undergo a completely stereospecific rearrangement under a variety of conditions via a mechanism involving neighboring-group participation by the acetal oxygen atom in the departure of the nucleofuge from C23. The reactions of equatorial (23S)-23-bromo-or (23S)-23-tosyloxyspirostanes with either the R (25R) or (25S) oriented 25-methyl group lead to the bisfuran products with inversion of configuration at C23. The reactions of the starting compounds with axial substituents (23R) at C23 require drastic conditions and result in the formation of the corresponding olefin accompanied by the rearranged product (in the case of the 25S isomer only).

Stereochemical arrangement of spiro [4. 5] decane derivatives by 15 N and 17 O NMR spectroscopy

1999

ABSTRACT: The relative axialÈequatorial position of spiro [4.5] decanes substituted in the 1, 4-positions by oxygen or nitrogen were assigned by 15N and 17O NMR spectroscopy. The substituent, chemical exchange and steric e† ects upon the chemical shifts are discussed. A linear relationship between 15N and 17O was found and the relative conÐguration of the chiral spiro atom was determined. Copyright 1999 John Wiley & Sons.

Lead tetraacetate–iodine oxidation of 23-spirostanols

Tetrahedron Letters, 2004

Reactions of 23R-and 23S-23-spirostanols in the 25R and 25S series with lead tetraacetate-iodine were studied. The reactions carried out at low temperature afforded D D -seco-iododialdehydes and C 22 lactones, while similar reactions performed in refluxing tetrachloromethane yielded 20-chlorolactones and their 21-acetoxy derivatives irrespective of the hydroxyl group configuration at C-23. The reaction mechanisms are discussed.

Unexpected Spiroproducts from the Reaction of N-Benzoylglycine withOrtho-Formylbenzoic Acids −3,5′-Dioxo-2′-Phenyl-1,3-Dihydrospiro[Indene-2,4′-[1,3]Oxazol]-1-yl Acetates: Establishments of Their Structure

Journal of the Chinese Chemical Society, 2009

This paper describes a method of preparation of new 3,5¢-dioxo-2¢-phenyl-1,3-dihydrospiro[indene-2,4¢-[1,3]oxazol]-1-yl acetate and its 5-chloro-and bromoderivatives as products of interaction of Nbenzoylglycine (hippuric acid) with corresponding ortho-formylbenzoic acids. The reaction carried out in acetic anhydride media in the presence of piperidine as catalyst. The novel spirocompounds were purified by column chromatography from multicomponent reaction mixtures. The composition of the spiroproducts was confirmed by C, H, N element analysis. The structure was established by IR, MS, 1 Hand 13 C-NMR analysis including COSY 1 H-13 C experiments.

Theoretical study of spiropentane, spiropentene and spiropentadiene

Tetrahedron, 2001

AbstractÐHF, MP2, and DFT calculations with 6-31G pp and 6-31111G pp basis sets were carried out for spiropentane, spiropentene, and spiropentadiene. The results of the calculations show that the NMR determination of HCH bond angle in spiropentane is more accurate than the value measured by electron diffraction. They also indicate that the assignment of one of the signals in the experimental NMR spectrum of spiropentene is in error. The calculations con®rm earlier conclusions drawn on the basis of low-level ab initio calculations concerning the operation of spiroconjugation in the investigated molecules. They also demonstrate that there is a need for further experimental studies of these molecules. q

Synthesis and stereochemistry of some new spiro and polyspiro-1,3-dithiane derivatives

Tetrahedron, 2008

The synthesis of new spiro and trispiro compounds with 2,4,8,10-tetrathiaspiro[5.5]undecane and 7,11,18,21-tetrathia[5.2.2.5.2.2]heneicosane units is reported. The structural analysis was carried out by NMR investigations and the X-ray single crystal molecular structure determined for one of the compounds. The barriers for the flipping of the 1,3-dithiane units are determined by variable temperature NMR experiments.

Synthesis of Spiro[2.2]pentanes and Spiro[2.3]hexanes Employing the Me3 Al/CH2 I2 Reagent

European Journal of Organic Chemistry, 2017

Substituted alkylidenecyclopropanes reacted with 5 equivalents each of Me3Al and CH2I2 at room temperature in hexane to give 1-mono-and 1,1-disubstituted spiro[2.2]pentanes in high yields. Surprisingly, the same reaction with substituted alkylidenecyclopropanes in CH2Cl2 afforded exclusively 1,1disubstituted spiro[2.3]hexanes. The transformation of 1,1diphenylspiro[2.2]pentane into 1,1-diphenylspiro[2.3]hexane was studied with the use of CD2I2 and a plausible mechanism was suggested. The reaction of substituted alkylidenecyclobutanes with the Me3Al/CH2I2 reagent in CH2Cl2 gave only 1,1-disubstituted spiro[2.3]hexanes.