The Structure of the So-Called “Ethyl Metaphosphate” (Langheld Ester)

Abstract

Phosphorus pentoxide reacts with ether to form bicyclotetraphosphate ester (II), cyclotetraphosphate ester (III), isocyclotetraphosphate ester (IV), and tetraphosphate ester (V). Phosphorus n.m.r. measurements show the content of the mixtures. The so-called "ethyl metaphosphate" (Langheld ester) ! is a mixture of III (50% t~45%), IV (36% to 25%), and V (14% to 30%). The product of the reaction of ether and phosphorus pentoxide 3 has recently become interesti?g as a re~gent ,for the synthesis of polysaccharides, polypeptides, and polynucleotides. 4Unfortunately, the ,

Dihydrogen Tetrametaphosphate, [P4O12H2]2–: Synthesis, Solubilization in Organic Media, Preparation of its Anhydride [P4O11]2– and Acidic Methyl Ester, and Conversion to Tetrametaphosphate Metal Complexes via Protonolysis

“…The reaction of 2 with 50 equiv of methanol at 23 °C afforded within 30 min the quantitative formation of methanolysis product [P 4 O 10 (OH)(OMe)] 2− (3). The 31 P{ 1 H} NMR spectrum of 3 revealed a triplet at −24.6 ppm Notably when 1 equiv of methanol was employed the quantitative conversion of 2 to 3 could still be achieved at room temperature within 24 h. Although the existence of the socalled "ethyl metaphosphate" (Langheld ester) has been reported, 25 compound 3 now represents the first example of a structurally characterized metaphosphate ester (See Figure 2).…”

Polyphosphate ester-catalysed cyclodehydration of monoesters of N-substituted 3-(indol-3′-yl)-5-methylcyclohex-4-ene-1,2-dicarboxylic acids; stereoselective synthesis of methyl 9-methyl-6-oxo-5-tosyl-5,6,6aβ,7β,8,10aβ-hexahydroindeno[2,1-b]indole-7α-carboxylate. X-Ray molecular structure of methyl 5-methoxy-9-methyl-6-oxo-5,6,6aβ,7β,8,10aβ-hexahydroindeno[2,1-b]indole-7-carboxylate

“…( (13).-A solution of the anhydride (5) (2 g, 4.6 mmol) and dilute H2S04 (15 ml) in a mixture of THF (75 ml) and acetone (15 ml) was heated under reflux for 4 h. The resulting solution was cooled, poured into water, and extracted with diethyl ether. The extract was washed successively with water and brine, dried, and evaporated to yield the diacid ( 13) as a pale yellow solid (1.66 -77, 120.81 and 121.40 (C-4 and -47,123.73 (C-5'), 124.82 (C-27, 125.11 (C-6' and -3 3 127.47 1273, 436 (20), 435 (M -H 2 0 , 60), 337 (18), and 181 ( 100).…”

“…164-167 "C (Found: M', 343.1419. ClgHzlNOs requires M , 343.1418); h,,,(EtOH) 221 (4.54), 276 (3.71), and 290 nm (3.76); vmax(Nujol) 3 180-2 560vbr, 1 740, 1 710, 1 450, 1 255, 1 200, 1 170,950, and 740 cm-'; 6,(90 MHz) 1.80 (3 H,s,m,, 3.00 (1 H, ddd, J1.6 6.13 and 10.94, J,,z 3.50 C02Me), 3.90 (3 H, s, OMe), 4.07 (1 H, br s, 3-H), 5.49 (1 H,br s,m,ArH);6,, 51.95 (C02Me), 65.05 (OMe), 108.45 (C-77, 112.41 (C-37, 118.80 (C-4'), 119.67 (C-4), 121.51 and 121.62 (C-2' and -5'), 122.38 (C-67, 123.46 (C-3'a), 112.40 (C-7'a), 134.51 (C-5), 173.73 (CO), and 182 (100), 167 (47), 116 (lo), and 93 (13).…”

“…Unfortunately, when the anhydride (5) was treated with AlCI,, the expected product (2) was not formed; instead bridged cyclic compounds ( 9) and (12) were isolated. In view of the results obtained from this study,2 we envisaged that an alternative approach to compound (2) might be effected via a route which involved cyclodehydration of the dicarboxylic acid (13) with polyphosphate ester (PPE). 5 If this cyclodehydration were to proceed in the desired manner, the C(1)-carboxylic acid group should be selectively transformed into another functionality such as an alcohol (18) or ester (14) so that it would not compete with the C(2)-carboxylic acid in the cyclodehydration.…”

“…Disappointingly, when the lactone (19) was treated with AlCl, in refluxing CHC1, it resisted intramolecular acylation and the starting lactone was recovered without any ketone (20) being detected (Scheme 1). The anhydride (5) was then converted selectively into its monomethyl ester (14) (Scheme 2) by, first, hydrolysis of the anhydride (5) to the dicarboxylic acid (13), followed by esterification selectively at the C(1)-carboxy group of the diacid (13) (5) - (10) iii - with BF,-methanol in tetrahydrofuran (THF). The structural assignment of the monoester thus formed, which showed a sharp singlet for the methoxy methyl at 6 3.69 in its 'H NMR spectrum, as compound (14), and not its isomer (17), was based on the consideration that the C( 1)-carboxy group was more easily accessible than the C(2)-carboxy group, and so should be esterified preferentially.…”