Ortho formic ester

On the other hand, 1,1,1-trisubstituted alkanes behave similarly to aldehydes, yielding pyrjdium salts (128) with identical substituents in positions 2 and 6. Thus, Dorofeenko and co-workers condensed 2 moles of acetophenone with 1 mole of benzotrichloride in the presence of perchloric acid obtaining 2,4,6-triphenjdpjTylium perchlorate with 1 mole of ethyl orthoformate, they obtained 2,6-diphenyl-pyrylium perchlorate (57) from o-hydroxyacetophenone, ortho-formic ester and perchloric acid, 4-ethoxybenzopyrylium perchlorate was formed. 

Aldehydes from Formic and Ortho-formic Esters. /0M°X + HC1... 

During the condensation of ethyl (3-chloro-2-quinoxaloyl)acetate 35a with ortho-formic ester in the presence of AC2O (65-70 °C), the formation of two substances was observed the main chlorine-containing reaction product 36a and a minor chlorine-free compound 38 (Scheme 3.13). The amoimt of compound 38 increased with increase in temperature, and at 100-105 °C it became the main reaction product. It was also shown that compound 36a can be obtained by heating the initial compound 35a with orthoformic ester at a higher temperamre (100-105 °C). The chain 35a 36a 38 was therefore investigated (Eiden and Bachmann 1973 ... 

These X -phosphorins 720 a-c also fail to react with carbonyl compounds. However, they are attacked by electrophiles (H or alkyl cations) at the C—2 position. In this manner new 1,1-diphenyl-2,3-benzo-X-phosphorins which are sustituted at positions C—2 (and C-4) can be prepared. Diazonium ions attack at C—4 to form azocompounds if an excess is used, C—2 is also substituted Hydrolysis with hot water affords 747. The reaction with ortho-formic acid ester forms a cyanine dye having a bridge at the C—4 positions 142 The experimen-... 

One can also acetalize carbonyl compounds completely without using the alcohol in excess. This is the case when one prepares dimethyl or diethyl acetals from carbonyl compounds with the help of the ortho formic acid esters trimethyl ortho formate HC(OCH3)3 or triethyl ortho formate HC(OC2H5)3, respectively. In order to understand these reactions, one must first clearly understand the mechanism for the hydrolysis of an orthoester to a normal ester (Figure 9.13). ft corresponds nearly step by step to the mechanism of hydrolysis of 0,0-acetals, which was detailed in Figure 9.12. The fact that the individual steps are analogous becomes very clear (see Figure 9.13) when one takes successive looks at... 

SYNS METHYLESTER KYSEUNY ORTHOMRAVENCI (CZECH) METHYL ORTHOFORMATE ORTHO-FORMIC ACID, TRIMETHYL ESTER ORTHOMRAVEN-CAN METHYLNATY (CZECH) TRIMETHO-XYMETHANE... 

Ortho Formic Acid.— Though the tri-hydroxy methane is not known we have proof that it is formed as the intermediate product in the foregoing reaction, because if we use, instead of potassium hydroxide, the analogous ethoxy compound, viz., potassium ethylate, C2HS—OK, there is obtained as the first result of the reaction the tri-ethyl ester of tri-hydroxy methane, or as it is known, ortho-formic acid, according to the following reaction ... 

This synthesis is capable of very wide application. But it has some defects. Thus the yield of aldehyde obtained in accordance with the original directions leaves much to be desired. The yield is very much decreased by the fact that a portion of tire phenol does not enter into the reaction, and another portion reacts with the chloroform to produce an ester of ortho formic add ... 

Methanesulfonic acid ortho formic acid esters Beckmann fragmentation... 

An alternative way to obtain end-group stabilized homopolymers is the etherification or total acetalization of the semi-acetal end groups. Alkylating agents, such as dimethyl sulfate or ortho-formic acid ester, epoxy alkanes, such as ethylene oxide or propylene oxide, and acetals in the presence of Lewis acids, or cation exchange resins are suitable. End-group etherified homopolymers have the additional advantage of alkali stability over esterified polymers, known also in copolymers blocked by comonomer components. 

Heferocyclics s. Ortho-formic acid esters, cyclic... 

In a series of organic acids of similar type, not much tendency exists for one acid to be more reactive than another. For example, in the replacement of stearic acid in methyl stearate by acetic acid, the equilibrium constant is 1.0. However, acidolysis in formic acid is usually much faster than in acetic acid, due to higher acidity and better ionizing properties of the former (115). Branched-chain acids, and some aromatic acids, especially stericaHy hindered acids such as ortho-substituted benzoic acids, would be expected to be less active in replacing other acids. Mixtures of esters are obtained when acidolysis is carried out without forcing the replacement to completion by removing one of the products. The acidolysis equilibrium and mechanism are discussed in detail in Reference 115. 

Alkyl formates or formic acid and its esters can be converted to trialkyl orthothioformates [74-77] which in turn can be converted to trialkyl orthoformates in good yields [78, 79], It has been reported that acid chlorides of higher carboxylic acids can also be converted to trialkyl orthothioformates [80], but thus far no reports appear in the literature on attempts to convert them to trialkyl ortho esters. 

Using ortho esters with a catalytic amount of p-toluenesulphonic acid instead of formic acid resulted in the formation of 2,3-disubstituted quinazolin-4(3//)-ones in 79-89% yield, Scheme 5.30. 

An alternative to the imidazolium salts as starting materials is the elimination of an alcohol from 2-alkoxy-l,2-dihydro-l f-imidazoles that are accessible by reaction of vicinal diamines with ortho-esters of formic acid [59-61] (see Figure 1.9). 

A 2- or 6-hydroxy-substituted purine can be prepared from the corresponding 4,5-diamino-pyrimidinol by cyclization with an acid, ester, ortho ester, or amide. If the ring closure is performed with reagents such as urea, alkyl chloroformates, urethanes, phosgene, and alkyl isocyanates, the 8-hydroxypurines are formed. Various xanthine and uric acid derivatives have been prepared by the condensation of 5,6-diaminopyrimidine-2,4-diols with formic acid. Purin-2-ol (1) was prepared by this route from 4,5-diaminopyrimidin-2-ol and ethyl orthoformate. ... 

The reagents used for the completion of the purine heterocycle are essentially the same as those used for the Traubc synthesis. The purine ring is formed by condensation with derivatives of formic acid or other carboxylic acids. Alternatively, formylation of the amino group is accomplished by a mixture of formic acid and acetic anhydride followed by cyclization. Alkyl esters or trialkyl ortho esters are also versatile synthons for ring closure. Moreover, heating in formamide or cyclization with urea or thiourea provides a satisfactory route. Condensations with isothiocyanates show unusual versatility leading to 2-sulfanylpurin-6-ols. From carbonic acid derivatives, cyclization is reported with chlorocarbonic esters, diethyl carbonate or carbon disulfide. 

Dialkyl acetals and ketals can easily be formed from carbonyl compounds with alcohols under acidic conditions. Some representative examples for the great variety of methods available for this transformation are given in Scheme 77. As is demonstrated, both simple alcohols themselves or formic acid ortho esters can be used for acetal formation in the presence of hydrochloric acid, toluenesulfonic acid °° or activated alumina (Montmorrilonite clay K-10). ° Owing to different carbonyl reactivities, regio- and chemo-selective differentiation is often realizable, as has been shown, for example, on androstane-3,17-dione (78). Acid-catalyzed acetalization selectively delivers the 3-ketal, whereas the sterically hindered 17-carbonyl function remains unaffected. Under neutral conditions the reactions are promoted by cata-... 

Oxazolo[2,3-fe]oxazoles (191 R = CF3, n-C7F,5) have been prepared by acid-catalyzed dehydration of A,A-bis(hydroxyalkyl)amides <82JFC(2l)359>. The imidazo[l,5-6f]imidazole (193) was prepared by reaction of aminoacetonitrile with excess trimethylorthoformate in the presence of catalytic amounts of formic acid <84JOCl2i2>. The reaction is believed to involve the initial formation of the imidate (192) which reacts successively with aminoacetonitrile and the ortho-ester to give the observed product. Pyrazolo[5,l-Z>]oxazoles (198) have been synthesized by reaction of hydrazino alcohols (195) with the Michael adduct (194), prepared from A-isobutylidene-r-butylamine and dimethyl-methoxymethylene malonate <93JHC1529>. The reaction is believed to involve cyclization of the intermediate hydrazones (196) to give pyrazoles (197), which subsequently cyclize to the bicyclic system with loss of dimethyl malonate. 

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