“…Accordingly, the reaction of POCl 3 with the hydroxyl groups present at the surface of the NDs followed by the hydrolysis of residual P–Cl groups during the washing step should ideally lead to phosphate groups linked to the surface through P–O–C bonds (ester bonds) (Scheme ). The transient formation of P–O–CO bonds (mixed anhydrides) by reaction with surface carboxylic groups is also a possibility, but such groups are highly unstable in the presence of water, and should revert to carboxylic acid groups during the washing step or storage under ambient conditions.…”
Surface phosphorylation of nanodiamond was performed by reaction with phosphoryl chloride in dichloromethane. Depending on the reaction conditions, P contents of up to 1.66 mmol/g were reached. Phosphorylation dramatically enhanced the thermal stability of nanodiamond under oxidizing conditions, shifting the oxidation temperature by up to 190 °C and dividing the oxidation rate by a factor of up to 160. The nature of the grafted phosphate species and their evolution during thermal treatment was followed using solidstate NMR.
“…Accordingly, the reaction of POCl 3 with the hydroxyl groups present at the surface of the NDs followed by the hydrolysis of residual P–Cl groups during the washing step should ideally lead to phosphate groups linked to the surface through P–O–C bonds (ester bonds) (Scheme ). The transient formation of P–O–CO bonds (mixed anhydrides) by reaction with surface carboxylic groups is also a possibility, but such groups are highly unstable in the presence of water, and should revert to carboxylic acid groups during the washing step or storage under ambient conditions.…”
Surface phosphorylation of nanodiamond was performed by reaction with phosphoryl chloride in dichloromethane. Depending on the reaction conditions, P contents of up to 1.66 mmol/g were reached. Phosphorylation dramatically enhanced the thermal stability of nanodiamond under oxidizing conditions, shifting the oxidation temperature by up to 190 °C and dividing the oxidation rate by a factor of up to 160. The nature of the grafted phosphate species and their evolution during thermal treatment was followed using solidstate NMR.
“…The amino groups of 1 were protected with the tert -butoxycarbonyl (Boc) group using di- tert -butyl dicarbonate (Boc 2 O) and triethylamine . Compound 2 was coupled with decanoic and palmitic acid using 1,3-dicyclohexylcarbodiimide (DCC) as a condensing agent in the presence of 4-(dimethylamino)pyridine (DMAP) to produce compounds 3a , b (Scheme ). The etherification procedure took place under phase-transfer conditions.…”
A novel class of potent human gastric lipase inhibitors, bis-2-oxo amide triacylglycerol analogues, was developed. These analogues of the natural substrate of lipases were prepared starting from 1,3-diaminopropan-2-ol. They were designed to contain the 2-oxo amide functionality in place of the scissile ester bond at the sn-1 and sn-3 position, while the ester bond at the sn-2 position was either maintained or replaced by an ether bond. The derivatives synthesized were tested for their ability to form stable monomolecular films at the air/water interface by recording their surface pressure/molecular area compression isotherms. The inhibition of human pancreatic and gastric lipases by the bis-2-oxo amides was studied using the monolayer technique with mixed films of 1,2-dicaprin containing variable proportions of each inhibitor. The nature of the functional group (ester or ether), as well as the chain length, at the sn-2 position influenced the potency of the inhibition. Among the compounds tested, 2-[(2-oxohexadecanoyl)amino]-1-[[(2-oxohexadecanoyl)-amino]methyl]ethyl decanoate was the most potent inhibitor, causing a 50% decrease in HPL and HGL activities at 0.076 and 0.020 surface molar fractions, respectively.
“…Chemical logic would dictate that acyl bis(trifluoroacetyl)phosphate ( 6 ) should have the most polarized acyl carbonyl group of the phosphate structures shown in Scheme and hence should be the most active acylating agent. It is relevant to note that acyl dichlorophosphoric acids, RC(O)OP(O)Cl 2 , are known to be reactive acylating agents, and, given that the inductive effect of OC(O)CF 3 (σ m , 0.56) is larger than that of Cl (σ m , 0.37), it is logical that acyl bis(trifluoroacetyl)phosphates should have superior acylation potential. A σ m value of 1.00 was evaluated for P(O)(OC(O)CF 3 ) 2 from the correlation shown in Figure ( R 2 = 0.84; data in Table ), and from this, a value of 0.71 was estimated for OP(O)(OC(O)CF 3 ) 2 by subtracting 0.29, which is the difference in the experimentally determined σ m values of P(O)(C 3 F 7 ) 2 and OP(O)(C 3 F 7 ) 2 . , 2 Correlation of the Hammet σ m values of selected groups X and the corresponding groups P(O)X 2 .…”
Reaction of acyl trifluoroacetates with phosphoric acid in the presence of trifluoroacetic anhydride
(TFAA) leads to the ready formation of acyl bis(trifluoroacetyl)phosphates, which are powerful
acylating agents. Formation of these species and the subsequent acylation reaction are carried
out, without added solvent, in a single in situ reaction process. In this reaction system, anisole is
rapidly acylated at ambient temperature using a variety of carboxylic acids giving the para isomer
exclusively. TFAA acts as an activating agent and can be recovered from the reaction system as
trifluoroacetic acid (TFA) and converted back to TFAA using a dehydrating agent, while phosphoric
acid behaves as a covalent catalyst in the process. This reaction system has many features which
are required elements of a clean alternative to the Friedel−Crafts process.
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