Acid-catalyzed rearrangements of an A(1)-nor-triterpenoid 2α,3α-epoxide

1989 ◽  
Vol 54 (2) ◽  
pp. 413-429 ◽  
Author(s):  
Jiří Klinot ◽  
Jiří Liška ◽  
Alena Forgáčová ◽  
Miloš Buděšínský ◽  
Jiří Protiva ◽  
...  
Keyword(s):  
Acidic Medium ◽  
Boron Trifluoride ◽  
Mass Spectra ◽  
Boron Trifluoride Etherate ◽  
Methyl Group ◽  
Unsaturated Alcohols ◽  
Acid Catalyzed ◽  
C Nmr

Reactions of 2α,3α-epoxide X, derived from 19β,28-epoxy-A(1)-nor-18α-oleanane, with acids proceed with migration of the 10β-methyl group into the position 2β, giving rise to unsaturated alcohols XII and XIV and diene IX. Reaction with boron trifluoride etherate afforded ketone XI in addition to XII and XIV. Olefin VIII rearranged in acidic medium to give olefins XXVI and XXVII. The rearranged products were converted into other derivatives and their structure was established by 1H and 13C NMR, IR, UV and mass spectra.

Tetracyclic triterpenes. VIII. The skeletal rearrangement of 3β-acetoxy-9α,11α-epoxy-5α-lanostan-7-one: 13- and 10-methyl group migration

1985 ◽  
Vol 63 (6) ◽  
pp. 1280-1286 ◽  
Author(s):  
Zdzisław Paryzek ◽  
Roman Wydra
Keyword(s):  
Acetic Anhydride ◽  
Spectral Data ◽  
Boron Trifluoride ◽  
Boron Trifluoride Etherate ◽  
Major Product ◽  
Chemical Transformations ◽  
Skeletal Rearrangement ◽  
Methyl Group ◽  
Group Migration

The boron trifluoride etherate catalyzed rearrangement of 3β-acetoxy-9α, 11α-epoxy-5α-lanostan-7-one (1) in acetic anhydride resulted in formation of 19(10 → 9β)abeo compounds 2 and 4 along with 18(13 → 12β)abeo compound 5, as the major product. These structures are supported by spectral data and chemical transformations. The possible mechanism of the rearrangement is discussed.

One-pot four component domino strategy for the synthesis of novel spirooxindole pyrrolizine linked 1,2,3-triazoles via stereo- and regioselective [3 + 2] cycloaddition reaction in acidic medium

RSC Advances ◽  
2016 ◽  
Vol 6 (11) ◽  
pp. 9297-9303 ◽  
Author(s):  
Rajeswari M. ◽  
Sudesh Kumari ◽  
Jitender M. Khurana
Keyword(s):  
Acidic Medium ◽  
Mass Spectra ◽  
Cycloaddition Reaction ◽  
One Pot ◽  
X Ray ◽  
H Nmr ◽  
C Nmr

An efficient, one-pot four component condensation has been reported for the synthesis of spirooxindole pyrrolizine linked 1,2,3-triazolesvia[3 + 2] cycloaddition. The structures were confirmed by1H NMR,13C NMR, mass spectra and X-ray.

The rearrangement of some epoxy podocarpanoic acids

1977 ◽  
Vol 30 (5) ◽  
pp. 1093 ◽  
Author(s):  
WS Hancock ◽  
LN Mander ◽  
RA Massy-Westropp
Keyword(s):  
Sulphuric Acid ◽  
Boron Trifluoride ◽  
Boron Trifluoride Etherate ◽  
Methyl Group

Rearrangement of the epoxides derived from the podocarpenoic acids (3b), (3d) and (5b) with boron trifluoride etherate gave compounds with the rosane skeleton, lacking substituents at C 13. The rearrangement involves the shift of a methyl group with concomitant lactonization. The unsaturated acids (3b) and (5b) undergo similar rearrangements when they are treated with boron trifluoride etherate or sulphuric acid.

Synthesis and Lewis acid induced isomerization of mono-, di-, and tri-spiro α-keto tetrahydro-furans and -pyrans

2006 ◽  
Vol 84 (10) ◽  
pp. 1388-1396 ◽  
Author(s):  
David G Hilmey ◽  
Peter R Selvaraj ◽  
Leo A Paquette
Keyword(s):  
Lewis Acid ◽  
Ground State ◽  
Boron Trifluoride ◽  
Boron Trifluoride Etherate ◽  
Ring Expansion ◽  
Stage Conversion ◽  
Ring Expansions ◽  
Third Stage ◽  
Synthetic Equivalent ◽  
Acid Catalyzed

The stereoselectivity of the acid-catalyzed ring expansion of dihydrofuranyl and dihydropyranyl 1,2-adducts to spirocyclic ketones 8 and 9 has been examined. These substrates have become readily available by the utilization of 1,3-dichloroacetone as a synthetic equivalent of cyclopropanone. The kinetically controlled isomerizations result in ring expansion to dispirocyclopentanones. Third-stage conversion to trispirocyclohexanones was shown to be possible in select examples. On a different front, the syn and anti pairs proved capable of interconversion by heating in the presence of boron trifluoride etherate. A push–pull fragmentation of the ketone ring is proposed to account for these epimerizations. Calculations have been performed to simulate transition state energies in the oxonium ion intermediates and to gain some idea of the preferred ground-state geometries of the final products.Key words: oxonium ion rearrangements, ring expansions, acid-catalyzed epimerizations, cyclopropanone equivalent, spirocyclic ethers.

Photolysereaktionen mit Komplexen des Typs CpFe(CO)2R (R = Me, Et, Ph)+ / Photolytic Reactions with Complexes of the Type CpFe(CO)2R (R = Me, Et, Ph)+

1979 ◽  
Vol 34 (8) ◽  
pp. 1070-1077 ◽  
Author(s):  
H. G. Alt ◽  
M. Herberhold ◽  
B. H. Edwards
Keyword(s):  
Mass Spectra ◽  
Hydrogen Abstraction ◽  
Carbonyl Groups ◽  
Subsequent Reaction ◽  
Methyl Group ◽  
Hydrocarbon Solvents ◽  
Photoinduced Reaction ◽  
Intramolecular Hydrogen ◽  
Derivatives Of ◽  
C Nmr

Photolysis of CpFe(CO)2R complexes [R = Me (1a), Et (1b), Ph (1c)] in hydrocarbon solvents results in loss of the group R and formation of the binuclear compound [CpFe(CO)2]2 (2). In the case of 1a, the photogenerated methyl group reacts to give methane by intramolecular hydrogen abstraction from the Cp ring, or by intermolecular hydrogen abstraction either from the solvent or another methyl group. The photoinduced dealkylation of the ethyl compound 1b is explained by β-elimination (to give ethylene) and subsequent reaction of the hydrido intermediates thus formed with unchanged 1b (to give ethane). The photolysis of 1c leads to phenyl groups which abstract hydrogen from the solvent to give benzene; a noticeable amount of diphenyl is also observed if benzene is used as a solvent.In the presence of potential two-electron ligands L [L = PMe3, P(OMe)3], only the carbonyl groups of CpFe(CO)2Me (1a) are photolabile, and substituted derivatives of the type CpFe(CO)(L)Me [L = PMe3 (3a), P(OMe)3 (4a)] and CpFe(L)2Me [L = P(OMe)3 (5a)] are formed.The photoinduced reaction of CpFe(CO)2Me (1a) and diphenylacetylene in solution gives metallocyclic derivatives containing either one or two diphenylacetylene units. On the basis of the IR, the 1H and 13C NMR, and the mass spectra, the complex CpFe(CO)(Ph2C2-COMe) (6a) is assigned a structure containing a vinyl-ketone unit in a five-membered metallocycle, while in CpFe(Ph4C4-COMe) (7a) a tetraphenylbutadienyl group appears to be incorporated into a seven-membered metallocycle

Cyclization of 17-ethylenedioxy-3α,5-cyclo-6,7-seco-5α-androstane-6,7-diol

1979 ◽  
Vol 44 (1) ◽  
pp. 128-144 ◽  
Author(s):  
Helena Velgová ◽  
Dietrich Zeigan ◽  
Günther Engelhardt ◽  
Antonín Trka
Keyword(s):  
Acetic Anhydride ◽  
Intramolecular Cyclization ◽  
Boron Trifluoride ◽  
Boron Trifluoride Etherate ◽  
Mass Spectrometric ◽  
Cyclic Ethers ◽  
Mass Spectrometric Data ◽  
Spectrometric Data ◽  
H Nmr ◽  
C Nmr

Intramolecular cyclization of 17-ethylenedioxy-3α,5-cyclo-6,7-seco-5α-androstane-6,7-diol (I) on treatment with p-toluenesulphonyl chloride in pyridine gives 17-ethylenedioxy-3α,5-cyclo-B-homo-7-oxa-5α-androstane (III) and 17-ethylenedioxy-3,5-methylene-6-oxaandrostane (II). The cyclic ethers II and III after deketalization and treatment with boron trifluoride etherate in acetic anhydride yield 3β,7-dihydroxy-6,7-secoandrost-5-en-17-one (XIV) along with a small quantity of 3β,5-cyclo-A-homo-6-oxa-5β-androstane-17-one (XIII). Proof of the structures in question is based on IR, 1H NMR, 13C NMR and mass spectrometric data.

Synthesis of 2-amino-5,7-dimethyl-4-oxopyrido[3,4-e]-1,3-thiazines

1983 ◽  
Vol 48 (12) ◽  
pp. 3426-3432 ◽  
Author(s):  
Dušan Koščík ◽  
Pavol Kristian ◽  
Ondrej Forgáč
Keyword(s):  
Spectral Data ◽  
Chlorine Atom ◽  
Mass Spectra ◽  
High Reactivity ◽  
Secondary Amines ◽  
Dimroth Rearrangement ◽  
H Nmr ◽  
New Synthesis ◽  
C Nmr

New synthesis of pyrido[3,4-e]-1,3-thiazines consisting in reaction of 2,6-dimethyl-4-chloronicotinoyl isothiocyanate with primary or secondary amines, or with benzaldehyde phenylhydrazone, is described. High reactivity of the chlorine atom does not allow isolation of the corresponding thioureas, arising as intermediates, except in the case of the benzylamino derivative. Structure of the products was unequivocally confirmed by their spectral data (IR, UV, 1H NMR, 13C NMR and mass spectra). The synthesized derivatives do not undergo the Dimroth rearrangement.

Sign in / Sign up

Export Citation Format

Share Document