Reactions of 5-Hydroxy steroids. XIII. The acid-catalysed reactions of Cholestane-4,5-diol 4-acetates and Cholestane-4,5-diol diacetates

1974 ◽  
Vol 27 (7) ◽  
pp. 1505 ◽  
Author(s):  
ETJ Bathurst ◽  
JM Coxon ◽  
MP Hartshorn
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Sulphuric Acid ◽  
Thionyl Chloride ◽  
Effect Of Substituents ◽  
Carbonium Ion ◽  
Rearrangement Process ◽  
Acid Catalysed Reactions

The reaction of 5α-cholestane-4α,5-diol 4-acetate (lb) with sulphuric acid-acetic anhydride-acetic acid occurs almost exclusively by loss of the 6α-proton to give cholest-5-en-4a-yl acetate (3) while dehydration with thionyl chloride-pyridine occurs predominantly (c. 80%) by loss of the 6β-proton. On reaction with D2SO4-DOAc-Ac2O, 5α-cholestane-4β,5-diol 4-acetate (7) undergoes backbone rearrangement to give olefins (9),(10) and (11) without incorporation of deuterium and thus excludes the intermediacy of olefins and cyclopropanes in the rearrangement process. The effect of substituents on these reactions has been rationalized by consideration of the initial conformation of the C5 carbonium ion.

2-Substituted and 2,6-disubstituted 1,4-benzoquinone 4-oxime acetates

1971 ◽  
Vol 24 (7) ◽  
pp. 1449 ◽  
Author(s):  
RK Norris ◽  
S Sternhell
Keyword(s):  
Acetic Anhydride ◽  
Physical Properties ◽  
Sulphuric Acid ◽  
Probable Mechanism ◽  
Effect Of Substituents ◽  
Infrared Data

The preparation and physical properties of 19 compounds in the title series are described. The acetates were prepared by treatment of the corresponding benzoquinone oximes or p-nitrosophenols with acetic anhydride in the presence of catalytic amounts of pyridine. The syn and anti isomers can be equilibrated in acetic anhydride solutions containing traces of sulphuric acid. The effect of substituents at C2 on the position of the syn-anti equilibria is very similar to their effect in the corresponding 1,4-benzoquinone 4-oximes. N.m.r. parameters, electronic and infrared data, photochemical syn-anti conversions, and the probable mechanism of the acid-catalysed equilibration are discussed.

THE ACETOLYSES OF THE ALPHA AND BETA METHYL D-GLUCOPYRANOSIDE TETRAACETATES

1955 ◽  
Vol 33 (1) ◽  
pp. 148-162 ◽  
Author(s):  
R. U. Lemieux ◽  
W. P. Shyluk ◽  
G. Huber
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Sulphuric Acid ◽  
Reaction Mechanisms ◽  
The Other ◽  
Isotopic Dilution ◽  
Other Hand ◽  
Anomeric Center ◽  
Reaction Routes ◽  
Isotopic Dilution Analysis

The acetolyses of the alpha and beta methyl D-glucopyranoside tetraacetates in 1:1 acetic acid – acetic anhydride 0.5 M with respect to sulphuric acid were followed at 25 °C. by isotopic dilution analysis of products isolated after various intervals of time. The reaction of the α-glucoside was found to proceed mainly with inversion of the anomeric center. On the other hand, the β-glucoside was found to undergo acetolysis with retention of configuration concurrent with anomerization. It was shown that the polarimetric changes observed in the course of the reactions could be satisfactorily accounted for on the basis of these reaction routes. Reaction mechanisms are suggested.

Photochemical reactions of azo compounds. VII. Studies of the photochemical reactions of azobenzene under various acidic conditions

1966 ◽  
Vol 19 (8) ◽  
pp. 1445 ◽  
Author(s):  
GE Lewis ◽  
RJ Mayfield
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Sulphuric Acid ◽  
Photochemical Reaction ◽  
Acetyl Chloride ◽  
Photochemical Reactions ◽  
Aluminium Chloride ◽  
Azo Compounds ◽  
High Yield ◽  
Acidic Conditions

An investigation has been made of the photochemical and dark reactions of azobenzene in acetic acid-ferric chloride and acetic acid-aluminium chloride mixtures for comparison with the corresponding reactions of azobenzene in sulphuric acid. The photochemical reactions resulted in cyclodehydrogenation of azobenzene to benzo[c]cinnoline, and small quantities of reduction products of azobenzene were also isolated. The formation of reduction products was again observed in the dark reactions, but there was no sign of cyclodehydrogenation. The significance of these observations is now discussed. Irradiation of azobenzene in acetyl chloride, or in acetic anhydride containing hydrogen chloride, resulted in a novel photochemical reaction in which NN?-diacetyl-4-chlorohydrazobenzene was formed in high yield.

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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