Baeyer-Villiger oxidation of Δ4-3-Oxo-steroids and 4,5-Epoxy-3-oxo-steroids. A route to some novel A-nor-steroids

1968 ◽  
Vol 21 (7) ◽  
pp. 1873
Author(s):  
JT Pinhey ◽  
K Schaffner
Keyword(s):  
Boron Trifluoride ◽  
Acidic Conditions ◽  
Oxygen Insertion ◽  
Acid Labile ◽  
Villiger Oxidation

Evidence is presented that the Baeyer-Villiger oxidation of Δ4-3-oxo-steroids yields enol-e-lactones which are further oxidized to β-epoxy-e-lactones. The latter are acid labile and rearrange to 5α-acyl-∂-lactones. The sequence appears to be stereospecific, and no 5β-acyl-∂-lactones could be isolated. Baeyer-Villiger oxidation of 4,5-epoxyoholestan-3-ones results in oxygen insertion between C3 and C4. The epoxy-e-lactones were not isolated, since they rearranged under the acidic conditions to give 5-acyl-4-oxacholestan-3-ones. The 5α-acyl epimers differ from the 5β-compounds, by undergoing an internal Claisen-type condensation to give A-norcholestans with a 2,5-lactone bridge. The photochemical, thermal, and boron trifluoride-catalysed conversion of the enol lactone (IIIa) into a-nor-5β-cholestan-3-one is reported.

scholarly journals Recent progress in oligonucleotide synthesis.

1996 ◽  
Vol 43 (1) ◽  
pp. 37-44 ◽  
Author(s):  
W Pfleiderer ◽  
S Matysiak ◽  
F Bergmann ◽  
R Schnell
Keyword(s):  
Acid Catalysis ◽  
Solid Phase ◽  
Chain Elongation ◽  
Synthetic Approach ◽  
Blocking Group ◽  
General Application ◽  
Acidic Conditions ◽  
Elongation Process ◽  
Acid Labile ◽  
Solid Phase Material

New blocking group combinations for the machine-aided oligoribonucleotide synthesis on solid phase material have been developed and tested regarding their general application. An acetal function for 2'-OH protection offers a series of advantages in the synthetic approach but special conditions have to be fulfilled in order to guarantee a selective cleavage of the temporary 5'-OH blocking group such as the dansylethoxycarbonyl or even the acid-labile dimethoxytrityl group in the chain elongation process. The final removal of the 2'-O-acetal function in the partially deblocked oligomer proceeds unexpectedly well under weak acidic conditions due to a supposed intramolecular acid catalysis.

Reactions of Epoxides Derived From 2′-(3″-Methylbut-2″-enyl)trifluoroacetanilides

1990 ◽  
Vol 43 (3) ◽  
pp. 609 ◽  
Author(s):  
KD Raner ◽  
BW Skelton ◽  
AD Ward ◽  
AH White
Keyword(s):  
Single Crystal ◽  
Potassium Carbonate ◽  
Ring Opening ◽  
Boron Trifluoride ◽  
Membered Ring ◽  
X Ray ◽  
Acidic Conditions ◽  
Nucleophilic Ring Opening

The intramolecular nucleophilic ring opening of the epoxides derived from 2′-(3″-methylbut-2″-enyl) trifluoroacetanilides has been investigated under both acidic and basic conditions. Boron trifluoride caused rearrangement of the epoxides to a ketone but no cyclization. Potassium carbonate in methanol caused regiospecific opening of the epoxides and generated dihydroindole products. The formation of a five-membered ring was confirmed by a single-crystal X-ray study of one of the products. The epoxides hydrolysed very readily in acidic conditions; the structure of one of the diol products was confirmed by a single-crystal X-ray study.

ChemInform Abstract: A Study of the Regioselectivity of Oxygen Insertion in the Baeyer- Villiger Oxidation of Bicyclo(2.2.1)heptan-2-ones.

ChemInform ◽  
2010 ◽  
Vol 22 (45) ◽  
pp. no-no
Author(s):  
P. HAMLEY ◽  
A. B. HOLMES ◽  
D. R. MARSHALL ◽  
J. W. M. MACKINNON
Keyword(s):  
Oxygen Insertion ◽  
Villiger Oxidation

Concise Synthesis of GB22 by Endo-Selective Siloxycyclopropane Arylation

2019 ◽  
Author(s):  
Hannah E. Burdge ◽  
Takuya Oguma ◽  
Takahiro Kawajiri ◽  
Ryan Shenvi
Keyword(s):  
Intramolecular Cyclization ◽  
Cross Coupling ◽  
Building Blocks ◽  
Ring Expansion ◽  
Dual Catalysis ◽  
Acid Labile

<div><div><div><p>The first synthesis of GB22 was accomplished by a con- cise, modular route. Two building blocks converged in a novel sp3-sp2 attached-ring coupling that used Ir/Ni dual-catalysis to reverse the regioselectivity of siloxycy- clopropane arylation. This cross-coupling proved general to access β-substituted tetralones via ring-expansion of indanone-derived siloxycyclopropanes. The congested, bridging rings of the GB alkaloids were completed using an aluminum-HFIP complex that effected intramolecular cyclization of an acid-labile substrate.</p></div></div></div>

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