AbstractThe hydrochloric acid‐catalyzed hydrolysis of phosphinates was studied on 1‐alkoxy‐3‐phospholene 1‐oxides, 1‐ethoxy‐3‐methylphospholane 1‐oxide, and 1‐ethoxy‐3‐methyl‐1,2,3,4,5,6‐hexahydrophosphinine 1‐oxide as the model compounds. Under the conditions applied, the isomerization of the 3‐phospholene moiety to the 2‐phospholene ring also occurred leading to mixtures of the corresponding 1‐hydroxy‐3‐phospholene oxide and 1‐hydroxy‐2‐phospholene oxide. According to our optimized method, using 3 equivalents (0.5 mL) of concentrated hydrochloric acid in 1 mL of water per ca. 2 mmol of the substrate at reflux, the completion required 3‐10 hour. The hydrolyses were characterized by pseudo‐first‐order rate constants and the isomerizations by rate constants. The application of p‐toluenesulfonic acid under microwave irradiation at 140°C in the hydrolysis of 1‐alkoxy‐3‐methyl‐3‐phospholene oxides associated with reaction times of 1‐3 hour. The reactivity order of the 5‐ and 6‐ring phosphinates in hydrolysis was set up.
Abstract Phosphinic acids may be efficiently esterified in microwave-assisted reactions with alcohols. Especially alcohols with longer alkyl chain are suitable reagents for direct esterifications. At the same time, the directamidation cannot be complete under such conditions. Hence, the tradional amidations via the phosphinic chloride intermediates have to be applied. The values of activation enthalpies
A Study on the Reduction of 4-Chloro-1,2-Dihydrophosphinine Oxides by Transfer Hydrogenation
作者:Rita Kovács、György T. Balogh、Krisztina Ludányi、László Drahos、György Keglevich
DOI:10.1080/10426507.2011.608100
日期:2012.1.1
Under the conditions of transfer hydrogenation by ammonium formate, the title compounds (6) were converted to a mixture of the corresponding 1,2,3,6-tetrahyidrophosphinine oxide (7), its dechlorinated derivative (8) and the respective 1,2,3,4,5,6-hexahydrophosphinine oxide (9). In the phenyl-substituted instance, the ratios of the components depended on the mode of heating (traditional heating or microwave irradiation), temperature, and the solvent (toluene or [bmim][BF4]) used. In the ethoxy-substituted series, the dechlorinated 1,2-dihydrophosphinine oxide (10b) was detected as an intermediate.
Synthesis of 1‐Aryl‐1,2,3,4,5,6‐hexahydrophosphinine 1‐Oxides
Possibilities for the synthesis of 1-(2,4,6-triisopropylphenyl-) 1,2,3,4,5,6-hexahydrophosphinine oxide (2) have been explored. The trivial method based on the hydrogenation of the corresponding dihydrophosphinine oxides (8a-e) was suitable only for the preparation of hexahydrophosphinine oxides containing a trimethylphenyl or methylphenyl group on the phosphorus atom (9a-c). The triisopropylphenyl product (2) was synthesized by the stepwise reduction of the double bonds of starting material 1. Hence, the ring contraction side reaction, observed during the catalytic hydrogenation, could be eliminated. The unusual reactivity was studied by quantum chemical calculations.