Reaction of hydroquinone with 2-ethoxyvinylphosphonyl dichloride

Abstract

Earlier, we have reported a one-step method for the synthesis of new cage-type phosphonates based on the condensation of 2-ethoxyvinylphosphonyl dichloride1 (1) with resorcinol and its derivatives in dioxane in the presence of trifluoroacetic acid.2,3 The presence of hydroxyl groups in the composition of bicyclic phosphonates having a rigid cage structure opens a possibility for the preparation of new macrocyclic and polymeric compounds. Vector 22 (Bruker) Fourier-spectrometer in the range of 400—3800 cm–1 for the Nujol mulls, MALDI-TOF mass spectrum was obtained on a ULTRAFLEX III mass spectrometer using plastic and metal plates, 2,5dihydroxybenzoic acid (2,5-DHB) was used as a matrix. 6,12-Dihydroxy-1-oxo-2,16-dioxa-1phosphatetracyclo[7.7.1.03,8.010,15]heptadeca-3,5,7,10,12,14hexaene (3). 2-Ethoxyvinylphosphonyl dichloride 1 (1.0 g, 5.3 mmol) was added dropwise to a refluxed mixture of hydroquinone 2 (1.17 g, 10.6 mmol) and trifluoroacetic acid (1.21 g, 10.6 mmol) in toluene (25 mL) (see Ref. 1) and the mixture was refluxed for 3 h with stirring. A precipitate formed was filtered off, washed with distilled water, and dried in vacuo until the weight was constant to obtain compound 3 (1.2 g, 78%), m.p. >350 °C. Found (%): C, 57.31; H, 3.71; P, 10.62. C14H11O5P. Calculated (%): C, 57.93; H, 3.79; P, 10.69. 1H NMR, δ: 2.59 (dd, 2 H, PCH2, JH,H = 3.58 Hz, JP,H = 16.14 Hz); 4.60 (dt, 1 H, CH, JH,H = 3.58 Hz, JP,H = 34.43 Hz); 6.60 (dd, 2 H, o-CH arom., JH,H = 8.60 Hz, JP,H = 1.79 Hz); 6.83 (s, 2 H, o-CH arom.); 6.85 (d, 2 H, m-CH arom., JH,H = 8.60 Hz); 9.73 (br.s, 2 H, OH). 31P NMR, δ: 15.05. IR, ν/cm–1: 1270 (P=O), 1594 (arom.), 3250—3550 (OH). MS (MALDI), m/z: 312. 68 [M + Na]+, 328.70 [M + K]+. In order to broaden the scope of bicyclic phosphonates of this series, we carried out the reaction of dichlorophosphonate 1 with hydroquinone (2) (Scheme 1), which resulted in the obtaining of the cage-type phosphonate 3. It should be noted that we considerably modified the procedure. The reaction was carried out in refluxing toluene instead of dioxane used earlier, in this case the reaction required 3 h instead of several days, and the product precipitated from the reaction mixture virtually did not require additional purification.