With orthoformic esters

Polyphosphonic acids are conveniently esterified by treatment with orthoformate esters with distillation of the lower-boiling alcohol. This procedure worked well for the acid (74), which readily dimerizes, and was also used to establish the structure of the dimer (75). ... 

On the basis of the formal similarity between 1,8-diamino-naphthalene and 3,4-diaminothienothiophene (1) the latter might be able to form a fused pyrimidine system on reaction with orthoformic ester or formamide. However, heating dimethyl 3,4-diaminothieno[2,3-6]-thiophene-2,5-dicarboxylate with acetic anhydride gave the corresponding MiV -diacetyl derivative, while 3,4-diacyloxy derivatives resulted from analogous reaction of dimethyl 3,4-dihydroxythieno-[2,3-6]thiophene-2,5-dicarboxylate with orthoformic ester and acetic anhydride."... 

The reaction of acid hydrazides with orthoformic esters proceeds via 2565,66 with elimination of alcohol to give 2-substituted 1,3,4-oxadiazoles (26). The reaction is mostly carried out with the reactants at the boiling point of the orthoformic ester or in an inert solvent at... 

Alkoxycyclopropanes. In the presence of MejSiCl the zinc amalgam reacts with orthoformic esters to generate organozinc carbenoids which are captured by alkenes. 

Although the reaction of dialkyl phosphites with orthoformic esters has been extended to triethyl trithioorthoformate," the preferred synthesis of formylphosphonate dithioacetals is usually the high-yield Michaelis-Arbuzov reaction of trivalent phosphorus compounds with the appropriate chlo-rodithioacetals.""" For the corresponding hemithioacetals, a Pummerer-type reaction of a-phos-phoryl sulfoxides with alcohols in the presence of iodine is usually the method of choice (Scheme 5.3). " ° However, hemithioacetal formation is solvent dependent and generally gives a moderate yield of product in a mixture with several other byproducts arising from transesterification reactions. 

Under carefnlly optimized experimental conditions, dialkyl 2,2-diethoxyethylphosphonates react with chlorine in reflnxing CCI4 under UV irradiation to provide dialkyl l,l-dichloro-2,2-diethoxyethylphosphonates. 5 These products can also be prepared in quantitative yield by reaction of diethyl 1,1-dichloro-1-formylmethylphosphonate with orthoformic esters in the presence of sulfuric acid. However, subsequent hydrolysis of these acetals gives modest yields of the corresponding aldehydes (30-40%). ... 

Razumov, A.L, and Moskva, V.V., Reaction of dialkylphosphorous acids with orthoformic esters, Zh. Obshch. Khim.. 34, 3125, 1964 J. Gen. Chem. USSR Engl. Transl.), 34, 3167, 1964. 

A methylene group activated by carbonyl and sulphonamido groups reacts with a neighbouring amino group on heating with orthoformate ester. 

Acetal formation by means of dimethyl sulfite925 requires almost the same conditions as does that with orthoformic esters. This procedure can be applied to cyclic but not to aliphatic ketones. 

Uracil and thymine derivatives are obtained from cyanoacetic acid and A -alkylurethanes. An amide 16 is formed first, which condenses with orthoformic ester to give the enol ether 17 aminolysis of 17 leads to 18 which on cyclization yields 5-cyanouracil 19 Shaw synthesis) ... 

As stated above, the synthesis of quinazoline derivatives can also be conducted in two stages, i.e., by the reaction of isatoic anhydrides with ammonia, amides, and various compounds containing the NH2 group followed by cyclization of the obtained anthranilic acid derivatives. Thus, the amino amides 157, formed during the action of aqueous ammonia on the anhydrides 61 (yields 61-73%), were brought into reaction with orthoformic ester, and this led to the quinazolinones 158 (yields 53-78%) [79],... 

The amino amides 159, obtained from the anhydrides 1 and 10 and primary amines, were converted into derivatives of 4-quinazolinone 160 with high yields by boiling with orthoformic ester [93-95],... 

The reactions of the anhydride 2 and the hydrochlorides of a-amino-p-indolyl- or a-amino-p-(5-methoxyindolyl)propionic acid 170 give high yields (97 and 88%) of the corresponding amides 171. When heated with orthoformic ester in the presence of TsOH the latter undergo cyclization to the condensed pentacyclic compounds 172 (yields 66 and 69% respectively) [101],... 

The aminoquinazolinones 177 were synthesized with yields of 26-71% by heating the hydrazides [formed from the anhydrides 1 or 10 and the hydrochlorides of disubstituted hydrazines] with orthoformic ester in the presence of triethylamine and pyridine in an atmosphere of nitrogen [103]... 

Ethyl cyanoacetate is cyclocondensed with thiourea under base catalysis giving 4-amino-2-thiouracil 26, onto which the second amino group is introduced (— 27). Oxidative desulfurization yields a sulfinic acid, which ehminates 802( 28) condensation with orthoformic ester transforms 28 into hypoxanthin (25). 

The formation of dialkyl-acetals and -ketals is generally restricted to aldehydes and reactive (unhindered) ketones. It is effected by acid-catalyzed reaction with alcohols, or more generally with orthoformic esters or acetals of low-boiling... 

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 ... 

Scheme 3.13 Condensation of ethyl (3-chloro-2-quinoxaloyl)acetate and l-(3-ethoxyquinox-alin-2-yl)butane-l,3-dione with orthoformic ester in the presence of AC2O...

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