scholarly journals Structure of the Rearrangement Product of Dihydromayurone with Boron Trifluoride in Acetic Acid-Acetic Anhydride at 50 °C

1979 ◽  
Vol 52 (7) ◽  
pp. 2161-2162 ◽  
Author(s):  
Haruo Sekizaki ◽  
Masaaki Ito ◽  
Shoji Inoue
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Boron Trifluoride ◽  
Rearrangement Product

Acetolytic cleavage of 2β,19-Epoxy-5α-cholestane involving a 1,2-Hydride shift to C2

1977 ◽  
Vol 30 (10) ◽  
pp. 2249 ◽  
Author(s):  
RE Gall ◽  
J Taylor
Keyword(s):  
Acetic Anhydride ◽  
Boron Trifluoride ◽  
Shift Reagent ◽  
Deuterium Exchange ◽  
Paramagnetic Shift ◽  
Nucleophilic Attack ◽  
Rearrangement Product ◽  
Hydride Shift ◽  
Carbonium Ion

Acetolytic cleavage of 2β,19-epoxy-5α-cholestane (1a) with boron trifluoride and acetic anhydride followed by hydrolysis gave the 2α,19- diol (2b), the only rearrangement product the 1α,19-diol (3b) and a mixture of olefins (4b). Deuterium exchange studies and the use of a paramagnetic shift reagent have shown that the reaction leading to the rearranged diol(3b) is not concerted and appears to involve an intermediate carbonium ion since hydride shift from both C 1 and C 3 occur. The formation of the 1α,19-diol (3b) as the only rearranged product can be rationalized as nucleophilic attack on the acetoxonium ion (8).

scholarly journals NOVEL REARRANGEMENT OF DIHYDROMAYURONE WITH BORON TRIFLUORIDE IN ACETIC ACID-ACETIC ANHYDRIDE

1978 ◽  
Vol 7 (11) ◽  
pp. 1191-1194 ◽  
Author(s):  
Haruo Sekizaki ◽  
Masaaki Ito ◽  
Shoji Inoue
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Boron Trifluoride

Synthetic routes to 2′,3′-cyclopropanated and 2′,3′-unsaturated nucleosides

1977 ◽  
Vol 55 (23) ◽  
pp. 3996-4001 ◽  
Author(s):  
Steve Yik-Kai Tam ◽  
Bert Fraser-Reid
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Boron Trifluoride ◽  
Synthetic Routes ◽  
Neutral Conditions

Cyclopropyl glycopyranosides which solvolyze via a stabilized cyclopropyl carbinyl-oxocar-bonium ion react under neutral conditions with nucleoside bases in nitromethane at 200 °C to give good yields of the corresponding cyclopropanated nucleosides. Under similar conditions hex-2-enopyranosides (which solvolyze by allyl-oxocarbonium ions) do not react. However, under catalysis by mercuric bromide or acetic acid, the corresponding 2′,3′ unsaturated nucleosides are formed although accompanied by appreciable amounts of 1′,2′-unsaturated-3′-nucleosides. Formation of the latter may be avoided if the hex-2-enopyranosides are first converted to the hex-2-enopyranosyl acetates by treatment with boron trifluoride and acetic anhydride. The derived acetates react with the nucleoside bases without catalysis to give anomeric mixtures of nucleosides, there being no trace of the unwanted 3′-nucleosides.

An unusual reaction of a bridged triterpenoid α-diketone with acetic anhydride

1991 ◽  
Vol 56 (12) ◽  
pp. 2917-2935 ◽  
Author(s):  
Eva Klinotová ◽  
Václav Křeček ◽  
Jiří Klinot ◽  
Miloš Buděšínský ◽  
Jaroslav Podlaha ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Nmr Spectroscopy ◽  
Acetic Anhydride ◽  
Spectral Methods ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mild Conditions ◽  
Condensation Products ◽  
Unsaturated Lactones ◽  
C Nmr

3β-Acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) reacts with acetic anhydride in pyridine under very mild conditions affording β-lactone IVa and γ-lactones Va and VIIa as condensation products. On reaction with pyridine, lactones Va and VIIa undergo elimination of acetic acid to give unsaturated lactones VIIIa and IXa, respectively. Similarly, the condensation of 20β,28-epoxy-21,22-dioxo-18α,19βH-ursan-3β-yl acetate (IIIb) with acetic anhydride leads to β-lactone IVb and γ-lactone Vb; the latter on heating with pyridine affords unsaturated lactone VIIIb and 21-methylene-22-ketone Xb. The structure of the obtained compounds was derived using spectral methods, particularly 1H and 13C NMR spectroscopy; structure of lactone IVa was confirmed by X-ray diffraction.

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