Anhydrides pivalic

CsHioO 107-87-9) see Protionamide Sildenafil 4 pcntcnoic pivalic anhydride (CioHisQr 178327-16-7) see Abacavir pentyl bromide... 

Figure 8.21 Separation of an olive oil sample after esterification with pivalic anhydride on a 10 cm x 2 mm I. D. silica gel cclumn with hexane-dichloromethane (4+1) containing 0.05% acetonitrile...

Bismuth(III) triflate is also a powerful acylation catalyst that catalyzes reactions with acetic anhydride and other less reactive anhydrides such as benzoic and pivalic anhydrides.113 Good results are achieved with tertiary and hindered secondary alcohols, as well as with alcohols containing acid- and base-sensitive functional groups. 

Pivalic acid, d679 Pivalic anhydride, d680 Pivaloyl chloride, d681... 

Dimerization of 2-hydroxy-4-methoxybenzaldehyde 208 was carried out using a mixture of pivalic anhydride and sulfuric acid. The product double 1,3-dioxane 209 was obtained in 96% yield (Scheme 98) <20000L1613>. Other anhydrides were less efficient. The product was used for the construction of the core unit of preussomerins <2004TL4877, 2004OBC2483>. 

Chiral a-amino acids The lithium anion of the N-protected glycine amides 3, prepared by reaction of the pyrrolidine with [bis(methylthio)methylene]glycyl pivalic anhydride (DMAP), is alkylated with high diastereoselectivity. The (S)-amino acid (5) is obtained on acid hydrolysis. 

The aliphatic alcohols are first heat-derivatized, with pivalic anhydride added directly to the oil. The solution is properly diluted with n-hexane and injected for the LC-GC run (Fig. 4). 

Steric effects were evaluated by a study of the DMAP-catalysed acylation of 1 y, 2y and 3y alcohols by acetic, propionic, isobutyric, isovaleric, and pivalic anhydrides in CH2C12 at 20 °C. In all cases the reaction kinetics could be described by rate laws containing a DMAP-catalysed term and an uncatalysed (background) term. Steric effects were evident in both reactions, but were generally greater for the DMAP-catalysed reaction. For example, the uncatalysed reactions between cyclohexanol and acetic and pivalic anhydrides differed about 500-fold, but for the corresponding DMAP-catalysed reactions the factor was 8000-fold. The implications of these findings for the kinetic resolution of alcohols were discussed.32... 

In the second step 20 is activated with oxalyl chloride to form a carboxylic acid chloride and treated in situ with a solution of (R)-4-benzyloxazolidine-2-thione 19 to produce 7 in 88 % yield. Alternatively the Crimmins group transformed 20 into a mixed pivalic anhydride 21 by means of pivaloyl chloride and triethylamine and converted it with the lithium salt of (7 )-4-benzyloxazolidin-2-one in 89 % yield to the corresponding oxazolidinone. In contrast to the sulfur analog, which is synthesized at temperatures between 0 °C and room temperature, the formation of an acyloxazolidinone had to take place at -78 °C. 

Hollander and co-workers [303—305] dealt with the problem in detail and developed a method for the isolation of hormones from blood, using Bio-Rad AG 50W-X2 (100—120 mesh) ion-exchange resin. Acylation with pivalic anhydride—methanol—triethylamine (20 1 1) was performed at 70°C for 10 min. The derivatives were purified with the aid of Amberlite IR-45 resin and benzene as a solvent. The dry residue was dissolved in 100 jul of benzene and 5 /il were injected directly on to a 60 cm X 4 mm I.D. column packed with 5% OV-1 on Chromosorb W HP after an isothermal period at 220°C for 12 min, the temperature was increased at 3°C/min up to 300°C. Calibration standards were injected immediately after the sample. Almost identical results were obtained for T3 by GC and radioimmunoassay [304], Other workers [306] applied the same procedure to the seeds and analysed pivalyl methyl esters of T3 and T4 on an 81 cm column packed with 3% of Dexsil on Chromosorb W HP at 305°C. 

This procedure has been used by Roush and Blizzard [33] in the synthesis of the macrocyclic mycotoxin verrucarin J (55). Thus, seco acid 54 was treated with 2 equiv of pivaloyl chloride and 3 equiv of triethylamine in dichloromethane (0.01 M) and the resultant mixed anhydride was treated in situ with 4-pyrrolidinopyridine (4-PP) to effect the ring closure at 23 °C. Verrucarin J (55) was obtained in up to 60% yield (Scheme 17). The mixed pivalic anhydride method has also been applied, e.g. to the synthesis of verrucarin B [34] and 4-epiverrucarin A [35] as the key cyclization step. 

Mixed pivalic anhydride 18 (42) is an example of selective mixed carboxylic anhydride. Selective aminolysis could be caused by the steric hindrance of the fert-butyl group. A mixed carbonic anhydride strategy has also been smdied to... 

Herrmann and co-workers showed that the 17-electron complex 62 may be subjected to electrochemical oxidation as well as reduction (54.55). The redox potentials of the respective halo complexes follow the expected trend for change in the halide ligands. In accordance with these electrochemical studies, both chemical oxidation and reduction reactions of 62 were found [Eqs. (49) and (50)]. Oxidation of the rhenium complex Re(CCMe3)(// -C5Me5)Cl2 by dioxygen results in cleavage of the neopentylidyne ligand from the metal center as pivalic anhydride and pivaloyl chloride. 

Rosenau, T., Potthast, A., Ebner, G., Kosma, P. Deoxygenation of amine oxides by in-situ-generated formic pivalic anhydride. Syn/eff 1999, 623-625. 

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