Preparation of selectively protected derivatives of 21-nor-5-pregnene-3β,20-diol

1990 ◽  
Vol 55 (2) ◽  
pp. 499-511 ◽  
Author(s):  
Vladimír Pouzar ◽  
Dalibor Sameš ◽  
Miroslav Havel
Keyword(s):  
Vinyl Ether ◽  
Ethyl Vinyl Ether ◽  
Protecting Group ◽  
Subsequent Removal ◽  
Reaction Conditions ◽  
Ethyl Vinyl ◽  
Hydride Reduction ◽  
Acid Catalyzed ◽  
Methyl Vinyl Ether ◽  
Derivatives Of

The preparation of selectively protected derivatives of the title diol (III) is described. Derivatives with protected hydroxyl in position 3 (IV, V and VI) were obtained by p-toluenesulfonic acid-catalyzed reaction of etienic acid (I) with dihydropyran, ethyl vinyl ether and methyl vinyl ether, respectively, and subsequent hydride reduction. The protection of the free primary hydroxyl in these compounds and the subsequent removal of the acetal protecting group in position 3 represents a suitable approach to 20-protected derivatives. The relative rates of cleavage of the acetal protecting groups and reaction conditions are discussed.

scholarly journals Acid Catalyzed Decomposition of Ethyl Vinyl Ether in 2,2,2-Trifluoroethanol.

1983 ◽  
Vol 37a ◽  
pp. 1-4
Author(s):  
Robert Eliason ◽  
Tapani A. Pakkanen ◽  
Tuula T. Pakkanen ◽  
Tapani Venäläinen ◽  
Birgitte E. R. Schilling ◽  
...  
Keyword(s):  
Vinyl Ether ◽  
Ethyl Vinyl Ether ◽  
Ethyl Vinyl ◽  
Acid Catalyzed

scholarly journals Dihydrofurans from α-diazoketones due to facile ring opening – cyclization of donor–acceptor cyclopropane intermediates

1996 ◽  
Vol 74 (12) ◽  
pp. 2401-2412 ◽  
Author(s):  
Elizabeth A. Lund ◽  
Isaac A. Kennedy ◽  
Alex G. Fallis
Keyword(s):  
Vinyl Ether ◽  
Ring Opening ◽  
Ethyl Vinyl Ether ◽  
Reaction Conditions ◽  
Substitution Pattern ◽  
Initial Product ◽  
Ethyl Vinyl ◽  
Enol Ethers ◽  
Donor Acceptor ◽  
Rhodium Acetate

A series of α-diazoketones, 8, 25, 28, 31, and 34, have been synthesized and their reaction with ethyl vinyl ether examined under various reaction conditions. In the presence of metal salts (Rh2(OAc)4, Pd(OAc)2, CuCl) the ethoxy-dihydrofurans 12, 37, 39, 41, and 43 are produced. Sensitized irradiation of the α-diazoketone 8 afforded the dihydrofuran 12 plus cyclobutanone 7, while direct photolysis of α-diazoketones 8, 25, 28, 31, and 34 gave the cyclobutanones 7, 38,40,42, and 44, respectively. A sample of the cyclopropylketone 45 was isolated from the rhodium(II) acetate mediated reaction of 34 and its facile rearrangement to dihydrofuran 43 demonstrated. Collectively, these results indicate that the initial product from the reaction of an α-diazoketone with an electron-rich alkene such as ethyl vinyl ether is a cyclopropylketone. The donnor–acceptor substitution pattern of this intermediate results in spontaneous rearrangement to a dihydrofuran. Thus a direct dipolar cycloaddition mechanism is not involved when α-diazoketones react with enol ethers under metal-mediated conditions. Instead, these reactions follow a cyclopropanation rearrangement or, more accurately, cyclopropanation – ring opening – cyciization pathway. Key words: diazoketone, rhodium acetate, dihydrofuran, cyclopropylketone, vinyl ether.

Cleavage of the Epimines of 1,6-Anhydrohexoses with Fluoride Anion

2005 ◽  
Vol 70 (12) ◽  
pp. 2075-2085 ◽  
Author(s):  
Jiří Kroutil ◽  
Klára Jeništová
Keyword(s):  
Fluoride Anion ◽  
Ring Cleavage ◽  
Protecting Group ◽  
Reaction Conditions ◽  
Aziridine Ring ◽  
Cleavage Reactions ◽  
Derivatives Of ◽  
Fluoro Derivatives

Aziridine ring cleavage reactions of five N-nosylepimines (2-6) having D-talo, D-galacto, D-manno, and D-allo configurations with potassium hydrogendifluoride under various reaction conditions have been performed. The cleavage regioselectively afforded diaxial isomers of vicinal amino-fluoro derivatives of 1,6-anhydro-β-D-gluco- and mannopyranose 7-11 in 51-94% yields. Removal of 2-nitrobenzenesulfonyl protecting group with benzenethiol has been attempted in the case of compound 10.

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