Imido ester hydrochlorides

Bisoxadiazoles are formed from bis(mono)imido ester hydrochlorides and mono(bis)carboxylic acid hydrazides when the free ester is used, an amidrazone (27) is often formed which cyclizes with the elimination of ammonia to give 28.73 The reaction proceeds in the presence of higher boiling solvents or by mixing the reactants at a temperature higher than 100°, the imido esters forming first in the reaction mixture. The reaction of semicarbazide [Eq. (2), R = NH2] with imido esters does not, of course, lead to 2-amino-1,3,4-oxadiazoles but to the isomeric l,2,4-triazolin-3-ones.72 The reaction of N-substituted imidochlorides with aromatic acid hydrazides in the... 

Primary and secondary amides and thioamides react with alkyl chlorofoimates with loss of CO2 or COS, forming iminium chlorides (82 equation 52). In some cases this method is complementary to the Pinner imido ester hydrochloride synthesis. The iminium salt (83 Scheme 6) formed by action of ethyl chloroformate on DMF is labile and decomposes rapidly to ethyl chloride. If the reaction is performed in the presence of NaBp4, the iminium salt (85) is isolable. Aryl chlorofoimates react in the same fashion with DMF or DMA, but in these cases the aryloxymethyleneiminium compounds are fairly stable, so this reaction is an important method for the preparation of compounds of this type. - Succinic acid monoamides, phthalic acid monoamides and related compounds are cyclized to iminium salts (86 equation 53) by treatment with acetic anhydride and HC104. ° With the aid of trifluoromethanesulfonic anhydride lactams and amides can be converted to dication ether salts (87) and (88 Scheme 7).22i.222... 

Acylguanidines 14 react with nitriles under reflux to give 4,6-disubstituted l,3,5-triazin-2-amines 15 400-402 Imido ester hydrochlorides, rather than the less reactive nitriles.401 may also be employed. In these cases, yields are 15% higher. 

Ethyl N-Methylacetimidate. A mixture of 58 g. (1 mole) of acetone and 600 cc. of a benzene solution of hydrazoic add containing 65 g. (1.5 moles) of hydrazoic add is adddi dropwise with stirring to 250 cc. of ethanol previously saturated with hydrogen chloride the temperature is kept below 25° by cooling, if necessary. When no more gas is evolved, the benzene and excess ethanol are evaporated the residue consists of the very hygroscopic imido ester hydrochloride. The free base, liberated by treatment with strong alkali, is dissolved in ether. The ether solution... 

A universal method for the preparation of 2,5-dialky 1 (aryl) -1,3,4-oxadiazoles is the reaction of acid hydrazides with imido esters or their hydrochlorides [Eq. (2)].1,2> 71-74... 

In an earlier investigation, aryl selenoesters have been prepared by the reaction of hydrogen selenide with imido esters (56 equation 24), but the yields were very low (56 R = Ph, 5.6% 56 R = p-tol 3%). The yield was somewhat improved by employing meAyl benzimidate hydrochloride (57 equation 23) as the starting material. ... 

Acylation of nitrogen compounds by imidic esters. It was mentioned above that synthesis of amidines from orthoesters proceeds through imidic esters, so that both classes of compound are normally treated together in reviews.819-821 Accordingly, also, it is, of course, possible to use imidic ester hydrochlorides as usually prepared from nitriles and to treat these with ammonia or amines.820 Care must be taken, however, with primary amines lest the imido group be also exchanged for the residue from the amine, particularly at higher temperatures ... 

Biphenyl-2,2 -diamine and ring-substituted biphenyl-2,2 -diamines are transformed into dibenzo[rf,/][l JJdiazepines 1 in various ways by reaction with ortho esters (Method A),169 with hydrochlorides of imido acid esters (Method B)170 or with the benzenesulfonates of pro-tonated nitriles (Method C).171 Selected examples are given. 

Method 5 170 A solution of biphenyl-2,2 -diamine (1.85 g, 10 mmol) in MeOH (20 mL) was treated with the hydrochloride of an imido acid ethyl ester (10 mmol) and the mixture was refluxed for the specified time. The mixture was cooled and the product was collected and rccrystallized (MeOH). 

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