Orthoformic ester

With Lewis acids as catalysts, compounds containing more than one alkoxy group on a carbon atom add across vinyl ether double bonds. Acetals give 3-alkoxyacetals since the products are also acetals, they can react further with excess vinyl ether to give oligomers (228—230). Orthoformic esters give diacetals of malonaldehyde (231). With Lewis acids and mercuric salts as catalysts, vinyl ethers add in similar fashion to give acetals of 3-butenal (232,233). 

The yield of this reaction for R=R =C2H is 73% (15). Reagents are less toxic than the corresponding sulfates and less volatile than the orthoformates. Esters of phosphoms oxo-acids having beta hydrogens undergo olefin elimination upon pyrolysis, usually beginning at 160—200°C. 

Bromobenzaldehyde has been prepared by the oxidation of -bromotoluene with chromyl chloride/ by saponification of the acetal from />-bromophenylmagnesium bromide and orthoformic ester/ by the oxidation of ethyl -bromobenzyl ether with nitric acid/ by the oxidation of /j-bromobenzyl bromide with lead nitrate/ and by the hydrolysis of i-bromobenzal bromide in the presence of calcium carbonate. ... 

Orthoformic ester and acetoacetic ester in presence of acetic anhydride form a hydroxyniethylene ester (Claisen),... 

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). 

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). ... 

The addition of Grignard reagents to aldehydes, ketones, and esters is the basis for the synthesis of a wide variety of alcohols, and several examples are given in Scheme 7.3. Primary alcohols can be made from formaldehyde (Entry 1) or, with addition of two carbons, from ethylene oxide (Entry 2). Secondary alcohols are obtained from aldehydes (Entries 3 to 6) or formate esters (Entry 7). Tertiary alcohols can be made from esters (Entries 8 and 9) or ketones (Entry 10). Lactones give diols (Entry 11). Aldehydes can be prepared from trialkyl orthoformate esters (Entries 12 and 13). Ketones can be made from nitriles (Entries 14 and 15), pyridine-2-thiol esters (Entry 16), N-methoxy-A-methyl carboxamides (Entries 17 and 18), or anhydrides (Entry 19). Carboxylic acids are available by reaction with C02 (Entries 20 to 22). Amines can be prepared from imines (Entry 23). Two-step procedures that involve formation and dehydration of alcohols provide routes to certain alkenes (Entries 24 and 25). 

Amino-1,2,4-triazole has been obtained from orthoformic ester and hydrazine hydrate in a sealed tube at 120° 1 by heating formylhydrazine at 150-210° 2-3-4 by heating N,N -diformyl-hydrazine at 160° 5 by decarboxylation of 4-amino-1,2,4-tria-zoldicarboxylic acid 6 by fusion of l,2-dihydro-l,2,4,5-tetrazine 6 and by heating l,2-dihydro-l,2,4,5-tetrazinedicarboxylic add above its melting point.4-6-7... 

The reaction of 4-substituted furazans 190 and 192 with morpholinonitroethene gave the corresponding 1,2,3-triazoles 191 and 193 in high yields (Equations 36 and 37). It should also be mentioned that, in order to facilitate the cycloaddition of azide, the reaction was carried out in the presence of orthoformic ester for removal of morpholine from the reaction medium, otherwise decomposition of the starting azide occurs <2000CHE343>. 

MgS04), and fractionally distilled to yield the orthoformate esters. 

A still different scheme is used for the preparation of the benzimidazole buterizine (74). Alkylation of benzhydrylpiperazine with substituted benzyl chloride 70 gives the intermediate 7U Nucleophilic aromatic displacement on this compound by means of ethyl amine leads to reduction of the nitro group then gives the diamine T. Treatment of that with the orthoformate ester of pentanoic acid serves to form the imidazole ring. There is thus obtained the peripheral vasodilating agent buteri zi ne (74). ... 

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."... 

Orthoformic esters, reaction with hexafluoroac-etone, 30 272... 

Schollkopf et al.187) synthesized a-alkyl-a-amino acids (186) by the alkylation of chiral 1-substituted 2-imidazolin-5-ones (185), which can be prepared from a-amino acid (S)-phenylethylamides and orthoformic esters. The optical yields of the products (186) were in many cases higher than 95 %. 

Dihydrazines react with 1,1-bis electrophile equivalents such as formaldehyde or orthoformic esters to give for example (581) from (580) (74MI51801). The interesting fused systems (582) and (583) were prepared by a similar path (73S355). 

The condensation of 1,4-diamines with a variety of carboxylic acid derivatives, e.g. imidate esters, orthoformic esters, /V-ethoxycarbonylthioamides (77JOC2530), nitriles and ethoxyacetylene, produces the cyclic amidine linkage —N = C(R)NH— (67AHC(8)2l, p. 40). Cyclic ureas, —NHC(0)NH—, have been similarly produced using carbonyl chloride, A, A -carbonyldi imidazole, carbon monoxide, thiocarbonyl chloride or carbon disulfide (67AHC(8)21, p. 38). 

Considering the results obtained in the reaction of orthoformic esters with CO and H2 (13) and the postulated instability of secondary and tertiary alkylcobalt carbonyls, the suggested role of alkylcobalt carbonyls in the course of this reaction seems questionable. Although a small amount of olefin is detected among the reaction products of sec-butyl-orthoformate with CO and H2, probably because of the low stability of secondary alkylcobalt carbonyls, and an 80 20 ratio is found between 2-methylbutanal and n-pentanal formed (13), it is still to be explained why the hydroformylation of 2-butene under the same conditions involving the same alkylcobalt intermediates gives a 29 71 ratio (4) of the same aldehydes. 

All of these examples illustrate the complexing ability of an ax-eq-ax sequence of oxygen atoms on a six-membered or of a cis-cis sequence on a five-membered ring. Attempts have been made to find other complexing sites on sugar molecules but with little success. The 0-3, 0-5, and 0-6 arrangement of hexofuranoses, which allows the ready formation of tri-dentate periodate (IS), and orthoformate esters (19), does not form stable complexes with metal ions. In solution the side-chain of 1,2-0-isopropylidene-a-D-glucofuranose (13) is in the extended zig-zag form... 

Orthoformic ester has been prepared by the treatment of a mixture of chloroform and alcohol with sodium 1 by the action of dry sodium ethylate on chloroform 2 or on an ether solution of chloroform 3 by the action of alcoholic sodium hydroxide on chloroform 4 and by the action of alcoholic hydrochloric acid on ethyl formimido ester5 or its mercuric chloride double salt.6... 

Wood and Comley have recently published 7 a method for the preparation of orthoformic ester, in which sodium and chloroform are added alternately to the absolute alcohol. A few runs were made according to their directions but the results were not as satisfactory as those obtained by the procedure given above. 

Piacenti s results for 1- and 2-pentene at high pressure would then fit in quite well with the fact that Takegami et al. (147-149) found that linear acylcobalt tetracarbonyls were much more difficult to isomerize than their branched-chain isomers. However, Piacenti et al. reject the possibility of an isomerization of alkylcobalt carbonyls in view of their work on the hydro-formylation of orthoformic esters (Section II, D,2). 

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