Ortho-formic acid

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 ... 

In fact 0. Fischer and Koerner have obtained hexamethylpara-leucaniline quantitatively by action of the methyl ether of ortho-formic acid on dimethylaniline [22]. The violet from dimethyl-aniline and chloranil is apparently identical with the ordinary one obtained by the copper process [23]. 

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. 

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. 

Gold forms a continuous series of solid solutions with palladium, and there is no evidence for the existence of a miscibility gap. Also, the catalytic properties of the component metals are very different, and for these reasons the Pd-Au alloys have been popular in studies of the electronic factor in catalysis. The well-known paper by Couper and Eley (127) remains the most clearly defined example of a correlation between catalytic activity and the filling of d-band vacancies. The apparent activation energy for the ortho-parahydrogen conversion over Pd-Au wires wras constant on Pd and the Pd-rich alloys, but increased abruptly at 60% Au, at which composition d-band vacancies were considered to be just filled. Subsequently, Eley, with various collaborators, has studied a number of other reactions over the same alloy wires, e.g., formic acid decomposition 128), CO oxidation 129), and N20 decomposition ISO). These results, and the extent to which they support the d-band theory, have been reviewed by Eley (1). We shall confine our attention here to the chemisorption of oxygen and the decomposition of formic acid, winch have been studied on Pd-Au alloy films. 

Treatment of a furan with ortho amino and cyano groups continues to be a viable route to fused pyrimidines. Thus, 2-amino-4,5-di-(2-furanyl)furano-3-carbonitrile produces 5,6-di-(2-furyl)furo[2,3-rf pyrimidin-4(//)-ones in 72% yield upon cyclization in acetic anhydride/formic acid <2006JFIC1129>. 

Treatment of the symmetrical triaminopyrimidine (50-1) with sulfuryl chloride ties up the two adjacent amines in a thiadiazole ring, protecting those groups from attacks in subsequent reactions. Reaction of the product (50-2) with ortho difluorinated benzylamine (50-3) results in the replacement of the pyrimidine amino group by that in the reagent most hkely by an addition-elimination sequence to afford (50-4). That amino group is then converted to the formamide (50-5) with formic acid. Exposure of the product to Raney nickel leads to a loss of sulfur and the formation of the transient intermediate (50-6). This cyclizes to a purine... 

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. 

The following solvents/reagents were used Concentrated formic acid and acetonitrile, both obtained from Promochem (Wesel, Germany) in HPLC grade quality. Isoproanol, ammonia (33%), methylene chloride and ortho-phosphoric acid (85 %) were supplied by Merck (Darmstadt, Germany) in analytical grade quality. 

A very important and versatile method en route to a NHC is the ring closure reaction with ortho-formate [18,34,36,43] (see Figure 1.7). Here a suitable diamine is reacted with a triester of formic acid resulting in a N=CH-N group that can be deprotonated to form a carbene. 

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). 

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