Alkoxy substituted acids

Unsubstituted aliphatic carboxylic acids are only very slowly further oxidized to the lower homologous acid in the oxidation of primary alkanols less than 2% of this acid are found. However, with substituted carboxylic acids the cleavage can become the main reaction. Thus anodic oxidation of phenylacetic acid at the nickel hydroxide electrode leads to 87% benzoic acid . Cleavages of similar to a lesser extent are observed with amino acids (Chapter 3.1) or P-alkoxy substituted acids (Chapter 2.4). 

The standard manufacturing method for tetraalkyl titanates, such as TYZOR TPT, or tetra- -butyi titanate, TYZOR TBT [5593-70 ] involves the addition of TiCl to an alcohol. In a series of reversible displacement reactions, the alkoxy substitution products and hydrochloric acid form as follows ... 

An acid-catalyzed substitution of a 6-oxo group on 2-aminopteridine-4,6-dione with hydrogen chloride in alcohols (65-100°, 3 hr, 80% yield) represents a convenient synthesis of the 6-alkoxy analogs. The reaction proceeds also with pteridine-2,4,6-trione and its 1-methyl and 1,3-dimethyl derivatives. While methoxylation of 2,4,7-trichloro-quinoline gives about equal amounts of 2- and 4-substitution, acid-catalyzed hydrolysis gives specific reaction at the 2-position only. ... 

Nitronates derived from primary nitroalkanes can be regarded as a synthetic equivalent of nitrile oxides since the elimination of an alcohol molecule from nitronates adds one higher oxidation level leading to nitrile oxides. This direct / -elimination of nitronates is known to be facilitated in the presence of a Lewis acid or a base catalyst [66, 72, 73]. On the other hand, cycloaddition reactions of nitronates to alkene dipolarophiles produce N-alkoxy-substituted isoxazolidines as cycloadducts. Under acid-catalyzed conditions, these isoxazolidines can be transformed into 2-isoxazolines through a ready / -elimination, and 2-isoxazolines correspond to the cycloadducts of nitrile oxide cycloadditions to alkenes [74]. 

Stepanov et a/.143,144 report the ring opening of the monoxide (116) to several 2-oxaadamantane derivatives, where 116 is readily obtained by perbenzoic acid oxidation of 35. Treatment of 116 under various conditions yields different products. Thus, with aqueous acid it yields l-hydroxy-3-hydroxymethyl-2-oxaadamantane (117), with alcohols (R = CH3, C2H5) in acidic or basic media 1-alkoxy-substituted (118), and with hydrochloric acid l-chloro-3-hydroxymethyl-2-oxaadamantane(119). l-Methyl-2-oxaadaman-tane (120) is prepared by LAH reduction of the carbonyl group in 35 to alcohol 121 and subsequent cyclization with acid.140,142... 

Treatment of a-hydroxy- or a-alkoxy-substituted hexahydro-oxazolo[3,4-r ]pyridin-3-ones with an acid allows for the generation of bicyclic iV-acyliminium ions which can then smoothly react with nucleophiles, usually with high diastereoselectivities (Scheme S3) <2001EJ01267, 1998SL206>. 

In one of the more frequently utilized Birch reactions (the reduction of alkyl/alkoxy-substituted naphthalenes), two reduction products are obtained as shown in Scheme 7.10. The acidity of the alcohol employed for protonation determines the ratio of these two products. For example, the ratio of the product hydrogenated in the substituted fused ring to the product hydrogenated in the unsubstituted fused ring was compared for methanol... 

Although the reaction of dihydropyridinium ions produced by the electrophilic attack of dihydropyridines has promise in organic synthesis, this reaction has not been extensively exploited. Some examples of their potential are provided by the acid-catalyzed reactions with indoles (80TL2341). An application of this reaction for an efficient synthesis of ( )-deplancheine is shown in Scheme 25. An interesting feature of this reaction was the use of the alkoxy-substituted dihydropyridine as a carbonyl precursor. 

Preparation of alkoxy alcohol Acid-catalysed unsymmetrical propylene oxide gives 1-substituted alcohols, resulting from the nucleophilic attack on the most substituted carbon. For example, propylene oxide reacts with alcohol in the presence of acid to give 2-methoxy-l-propanol. 

Benzhydrylamines are better suited than benzylamines as acid-labile linkers for amines. The MBHA linker ( methylbenzhydrylamine ), which is usually used to prepare peptide amides (see Section 3.3), can also be used as a linker for amines (Entry 1, Table 3.21). Hydrogen fluoride is, however, required as the cleavage reagent. Easier to cleave are alkoxy-substituted benzhydrylamines (Entries 2-5, Table 3.21), which can be prepared from the corresponding benzhydryl chlorides [263] or by reductive alkylation [410] or solvolysis [411] of the Rink amide linker. In the case of benzhydrylamines linked to polystyrene as benzyl ethers, treatment with TFA can lead to the release of the linker into solution (acidolysis of the benzylic C-O bond, see Figure 3.18). 

Because alkoxy substituted alcohols are acid sensitive the support must be either neutral or even basic. That the presence of a basic promoter is needed can be seen by a strongly decreased activity when the Ca and Mg, which are present originally in the carrier, are removed by washing with 2N HC1. Catalysts prepared with additional basic metals as chlorides (1% metal on catalyst) were tested at 200°C. At these temperatures there are only very small differences between the metals. Figure 2 shows a plot of ionic radius versus conversion of MEA. The best promotors are potassium and calcium. 

Various alkoxy-substituted phenylacetones 34 are used to synthesize a series of 2-benzopyrylium salts 35 by acid-catalyzed acylation [66DOK( 166)359 66ZOR1492 70KGS(2)196,70KGS(2)213 70ZOR1118]. Interestingly, in all cases the alternative pathway of acylation of 34 (R1 = H and R2, R3 are not equal to H) was not observed, and isomeric 2-benzopyrylium salts 36 were not obtained. 

Acylation of homoveratric esters 51 leads to the stable 3-alkoxy-substituted cations 52, whereas the use of homoveratric acid 51 (R = H) gives the unstable 3-acyloxy-substituted salts 53, which are easily hydrolyzed to ring-opened ketoacids 54 [70KGS(2)200]. 

Methoxy- and amino-substituted disilenes behave differently from 1529. Irradiation of a hexane solution of 20 in the presence of various alcohols at room temperature afforded 1,1-dialkoxyhydrodisilanes 28a-32a together with a small amount of the regioisomers 28b-32b (Scheme 5). Thus alkoxy groups direct the alcohol addition to the alkoxy-substituted silicon atom. The ratios of regioisomers (a/b) were 100/0 (EtOH, 28), 96/4 (i-PrOH, 29) and 93/7 (t-BuOH, 30). Steric bulkiness is not the only factor that determines the regioselectivity, since bulky but acidic alcohols, such as 2,6-dimethylphenol... 

Electropolymerization in acidic media affords free-standing films that are believed to contain varying degrees of cross-linking [267,292,304]. The miscibility of aniline with water allows for a variety of aqueous oxidants, such as ammonium peroxydisulfate, to be used [305]. Chemical polymerization of aniline can also be performed in chloroform through the use of tetrabutyl ammonium periodate [306]. Accordingly, a number of alkyl [301] and alkoxy-substituted [307] aniline derivatives have been chemically polymerized. Unfortunately, functionalization of the aniline nucleus often leads to a decrease in performance in the resulting polymers [308,309]. 

Gyurosiova, L., Laitinen, L., Raiman, J., et al. Permeability profiles of M-alkoxy-substituted pyrrolidinoethylesters of phenylcarbamic acid across caco-2 monolayers and human skin. Pharm. Res. 19(2) 162-168, 2002. 

Exposure of the (cycloalkenyl)methyl carbamates 304 to iodosylbenzene in the presence or absence of Rh2(OAc)4 gives the tricyclic aziridines 305 (Scheme 88) (02OL2137). Reactions of 305 with nucleophiles, facilitated with tosic acid or lithium perchlorate, proceed with cleavage of the C-N edge bond and afford the tf 7 z-spirooxazolidinones 306. Intramolecular aziridination of the indolyl carbamate 307 with DAIB, on the other hand, requires Rh(II)-catalysis and leads directly to the acetoxy-substituted YDi-spirooxazolidinone 308 (Scheme 88) (02OL2137). When iodosylbenzene is used instead of DAIB and alcohols are available in the reaction medium, alkoxy-substituted syn-spirooxazolidinones 309 are obtained. Whereas the conversion of 304 to 305 appears to proceed by direct cyclization of intermediate iminoiodanes, the production of 308 from 307 was attributed to the intervention of a rhodium nitrene, which collapses to 308 through zwitterionic intermediates (02OL2137). 

For halogen or alkoxy-substituted polymers Tg values are low (between -60 and —100° C). Alkoxy poly phosphazene with Ci - C3 substituents are elastomers. Higher alkoxy- or aryloxy-substituted polyphosphazenes are thermoplastics. Fluoroalkoxypolyphosphazenes exhibit a good stability toward diluted acids and bases. Some of them have outstanding thermal stability and good flame-retardant properties. 

The relatively acidic a hydrogens of amino- and alkoxy-substituted Fischer carbenes are readily removed... 

Anions formed from group 6 and manganese Fischer carbene complexes undergo aldol condensations with aldehydes and ketones. Allylic carbenes exclusively react in the y position with aldehydes affording dienyl-substituted carbenes. For alkoxy-substituted carbenes, the presence of an excess Lewis acid see Lewis Acids Bases), such as boron trifluoride etherate, titanium tetrachloride, or tin tetrachloride is required for the reaction to proceed in reasonable yield. The initial aldol product can be isolated without elimination (Scheme 12). ... 

Few examples of [4 + 2] cycloadditicMis of aromatic aldehydes with simple alkyl-, halo- and alkoxy-substituted 1,3-dienes exist. Ansell and Charalambides found that benzaldehydes substituted with electron-withdrawing groups such as nitro and cyano undergo thermal cycloaddition.Other benzaldehydes were found to cycloadd only in the presence of p-toluenesulfonic acid. 

Alkyl- and alkoxy-substituted quinoxalines are readily oxidized using 60-90% hydrogen peroxide in acetic acid. although quinoxaline itself may give rise to quinoxaline-2,3-dione under these conditions.It has been reported that, although uncommon, an explosion hazard exists using this procedure. ... 

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