Pseudo-esters

Very likely, the pseudo-esters are susceptible to saponification as well. 

CycUzation catalyst. Newman and Courduvelis5 used the reagent as catalyst for the condensation of o-benzoylbenzoic acid methyl ester (1) with methyl chloro-carbonate. The product (2) decomposes on heating to give the pseudo ester (3). 

Newman and Lola236 observed that, when 3-chloro-3-phenylphthalide (1) is allowed to react with methanol in the cold, the pseudo ester (2) produced on standing in the presence of the hydrogen chloride reacts rapidly by addition of methanol to the carbonyl group to give the normal methyl ester (3). They found that added urea effectively neutralizes the mineral acid and suppresses the reaction of (2) to give (3). This... 

The treatment of 100 (R = R = Ph) with boron trifluoride etherate proved to be a useful preparative alternative for the formation of 102. The reaction of 100 (R = R = C02Me) with boron trifluoride etherate affords a 7-pyrone 105 a product of type 102 is not observed. On treatment with methanol, the pseudo-ester 103 is formed and, in the presence of sulfuric acid, 103 is converted to the methyl ester 104 (Scheme 12). 

For this reason, the reaction of quinolinic anhydride with water is surprising . With methanol, both possible esters are formed but the proportion of 2-methoxycarbonylnicotinic acid increases with time (the 3-methyl ester gives the isomer almost completely when boiled in ethyl acetate). With one molecular equivalent of methanol at room temperature, the anhydride produces the pseudo-ester (15) which forms a crystalline hydrate (16). The 3-methyl ester arises from (15), and the relationships of these compounds have been represented by the scheme... 

After examining a number of model systems, Pearlman found that substrates related to the substituted cyclohexenol 33 to be best for this cycloaddition-reteroaldolization sequence (Scheme 3.6) (20). For example, photoinduced intramolecular cycloaddition of the pseudo ester 33 afforded the tetracyclic cyclobutane derivative 34. Hydrolysis of this substance produced the ketoester 35 which underwent Baeyer-Villager oxidation to generate the retroaldol substrate 36. Treatment of 36 with acid effected the desired retroaldolization and gave the lactol methyl ether 37 which has the acetic acid, aldehyde and alcohol functionality cis-oriented on the cyclohexane skeleton. 

Other pseudo-halides are used for carbonylation. Phenyl tluorosulfonate (484) can be carbonylated to give benzoate[337]. Aryl(aryl)iodonium salts[338], aryl(alkenyl)iodonium salts (485)[339], and arylialkynyl)iodonium salts (486)[340] are reactive compounds and undergo carbonylation under mild conditions (room temperature, 1 atm) to give aryl, alkenyl, and alkynyl esters. lodoxybenzene (487) is carbonylated under mild conditions in... 

Enone formation-aromatization has been used for the synthesis of 7-hydro-xyalkavinone (716)[456]. The isotlavone 717 was prepared by the elimina-tion[457]. The unsaturated 5-keto allyl esters 718 and 719, obtained in two steps from myreene. were subjected to enone formation. The reaction can be carried out even at room temperature using dinitriles such as adiponitrile (720) or 1,6-dicyanohexane as a solvent and a weak ligand to give the pseudo-ionone isomers 721 and 722 without giving an allylated product(458]. 

Conversely, when A-alkyl tryptophan methyl esters were condensed with aldehydes, the trans diastereomers were observed as the major products." X-ray-crystal structures of 1,2,3-trisubstituted tetrahydro-P-carbolines revealed that the Cl substituent preferentially adopted a pseudo-axial position, forcing the C3 substituent into a pseudo-equatorial orientation to give the kinetically and thermodynamically preferred trans isomer." As the steric size of the Cl and N2 substituents increased, the selectivity for the trans isomer became greater. A-alkyl-L-tryptophan methyl ester 42 was condensed with various aliphatic aldehydes in the presence of trifluoroacetic acid to give predominantly the trans isomers. ... 

The pyrylocyanine obtained by Strzelecka and Simalty from 2,6-diphenyl-4-phenacylpyrylium and orthoformic ester (cf." Section II, B, 1, a) has the structure of a pseudo base. Accordingly, its protonation is accompanied by dehydration leading to a triple pyrylium cation (see Scheme 4). 

Quaternization of harman (235) with ethyl bromoacetate, followed by cyclization of the pyridinium salt 236 with 1,2-cyclohexane-dione in refluxing ethanol yielded an ester which on hydrolysis gave the pseudo-cross-conjugated mesomeric betaine 237. Decarboxylation resulted in the formation of the alkaloid Sempervirine (238). The PCCMB 237 is isoconjugate with the 11/7-benzo[u]fluorene anion—an odd nonalternant hydrocarbon anion—and belongs to class 14 of heterocyclic mesomeric betaines (Scheme 78). 

The des-ethyl derivative 251 of Flavopereirine was prepared similarly starting from 2-chloro isonicotinic acid methyl ester 250 (Scheme 81). The resulting hydrochloride was converted into the pseudo-cross-conjugated... 

Table 9. Pseudo-first-order rate constants for the release of p-nitrophenol in the reactions of optically active esters in a CTAB micelle...

Fourier transform infrared (FTIR) spectroscopy (NaCl) shows no remaining carboxylic acid (1696 cm-1, carbonyl) but only ester groups (1736 cm 1, carbonyl) Mn(SEC) = 6530 Mn(1H NMR) = 1640 theory for third generation Mn = 2570.65 Polyesters of higher generation were synthesized according to this pseudo-one-step procedure and were analyzed by SEC, VPO, and 111 NMR.65... 

A. Pentoses.—t-Ascorbic acid 2- and 3-phosphates, together with their phosphate esters, give a characteristic colour with ferric chloride and this colour reaction has been used in a study of the hydrolysis of L-ascorbic acid 3-phosphate (58). The acid-catalysed, pseudo-firsi-order hydrolysis proceeds with P—O bond fission, as does the bromine oxidation of its phenyl ester. Both of these observations can be rationalized if (58) is... 

The non-equivalence of the ester protons in the monomethyl- and monophenyl-phosphinic ester function, as in (44, Ch = chalkogen), has been studied. Compounds of type (45) have some interesting stereochemistry. They are prepared from racemic secondary butyl alcohol, and the presence of three signals in the P n.m.r. spectrum confirms that the phosphorus atom is the centre of pseudo-asymmetry. A 1 2 1 triplet is observed which is attributed to the presence of equal amounts of two mesa forms, (45) and (46), which have different values of Sp (outer peaks), and two racemic forms, (47) and (48), which have identical values of 8p (central peak). 

A complicating feature of studies of carboxylic acid and their corresponding esters, having proximate keto or formyl groups, is the occurrence of ring-chain tautomerism, as in Scheme 1 (Valters and Flitsch, 1985). The rates of conversion of the ring and chain acids ([1] and [2] R = H) are rapid. However, both the pseudo and normal esters ([1] and [2], R = alkyl or aryl) can be isolated in favourable circumstances. The latter esters can also be interconverted by base- or acid-catalysis under suitable conditions. 

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