Polyphosphoric Acid Trimethylsilyl Ester Promoted Intramolecular Acylation of an Olefin by a Carboxylic Acid:  Convenient Construction of C-18-Functionalized Δ14-Hecogenin Acetate†

2003 ◽  
Vol 5 (22) ◽  
pp. 4061-4064 ◽  
Author(s):  
Wei Li ◽  
Philip L. Fuchs
Keyword(s):  
Carboxylic Acid ◽  
Polyphosphoric Acid ◽  
Trimethylsilyl Ester ◽  
Hecogenin Acetate

Cyclization of Phenacyl 2-{[2,2-Di(ethoxycarbonyl)vinyl]amino}benzoate

1998 ◽  
Vol 63 (4) ◽  
pp. 520-524 ◽  
Author(s):  
Pavel Hradil ◽  
Lubomír Kvapil ◽  
Jan Hlaváč ◽  
Karel Lemr ◽  
Juraj Ševčík
Keyword(s):  
Sulfuric Acid ◽  
Carboxylic Acid ◽  
Ethyl Ester ◽  
Polyphosphoric Acid ◽  
Diphenyl Ether ◽  
Thermal Cyclization ◽  
Prolonged Heating ◽  
Independent Synthesis ◽  
Hydrolysis Of

Reaction of phenacyl anthranilate (1) with diethyl (ethoxymethylidene)malonate afforded phenacyl 2-{[2,2-di(ethoxycarbonyl)vinyl]amino}benzoate (2) which on heating in polyphosphoric acid underwent degradation. Thermal cyclization of 2 in diphenyl ether gave phenacyl 3-(ethoxycarbonyl)-4-oxo-1,4-dihydroquinoline-8-carboxylate (4). The phenacyl group did not cyclize even on prolonged heating at 250 °C. Heating in sulfuric acid resulted in hydrolysis of the ethyl ester under formation of 4-oxo-8-[(phenacyloxy)carbonyl]-1,4-dihydroquinoline-3-carboxylic acid (6). The structure of 4 was confirmed by an independent synthesis.

Polyphosphoric Acid Trimethylsilyl Ester (PPSE) in the Synthesis of Heterocycles

ChemInform ◽  
2005 ◽  
Vol 36 (9) ◽  
Author(s):  
Monica E. Hedrera ◽  
Isabel A. Perillo
Keyword(s):  
Polyphosphoric Acid ◽  
Trimethylsilyl Ester
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