ABSTRACT This work presents the study results on the acid‐catalyzed cascade condensation of p ‐toluenesulfonamide with glyoxal in H 2 SO 4 in order to synthesize aza‐ and oxaazaisowurtzitanes—a platform for promising high‐energy‐density compounds—and explore their formation processes. The effects of the ratio of starting reactants, acidity, reaction medium concentration, and temperature on this process were studied in detail. Five novel compounds were derived, including four oxaazaisowurtzitanes comprising one to three aza groups, and one condensation intermediate. The most favorable conditions for the formation of the resultant caged compounds were established and some new regularities of the process were revealed. For instance, the reaction medium concentration was discovered for the first time to influence the generation process of oxaazaisowurtzitanes via direct condensation. The limiting stage of the cage formation process of oxaazaisowurtzitanes was identified. The formation rate of the oxaazaisowurtzitanes was shown to be dependent on their structure. The factor dramatically reducing the yield of the oxaazaisowurtzitanes at elevated synthesis temperature was also revealed.

The synthesis of substituted 2,4,6,8,10,12-hexaazaisowurtzitane via direct condensation is challenging. The selection of starting ammonia derivatives is very limited. The important step in developing alternative synthetic routes to these compounds is to investigate their formation process in detail. Here, we examined an acid-catalyzed condensation between benzyl carbamate and glyoxal in a ratio of 2:1 in a range of polar protic and aprotic solvents, and discovered a new process occurring during the cascade condensation of glyoxal with ammonia derivatives as well as discovered several processes hindering the formation of caged compounds. More specifically, a cyclic compound, N,N′-bis(carbobenzoxy)-3,6-diamino-1,4-dioxane-2,5-diol, was found to form at the early stage of condensation under low acidity conditions. The formation of this compound is governed by an easier condensation of alcohol groups compared to the amide ones. The condensation intermediates, N,N′-bis(carbobenzoxy)ethan-1,2-diol, N,N′,N″-tris(carbobenzoxy)ethanol, and N,N′,N″,N‴-tetrakis(carbobenzoxy)ethan, were obtained at a higher acidity. A range of solvents were identified: those that react with benzyl carbamate, those that promote the progress of side processes, and those that promote precipitation of condensation intermediates. A few byproducts were isolated and identified. It was found that DMSO exhibits a strong deactivating ability, while CH3CN exhibits a strong activating ability towards the acid-catalyzed condensation process of benzyl carbamate with glyoxal.

Here, we explored in detail an acid-catalyzed condensation of glyoxylic acid or its ethyl ester with several carboxamides of different basicity, or with mesyl amide, to furnish diaminoacetic acid derivatives. The most suitable synthesis conditions and the reaction catalysts were identified. Properties such as structure and basicity of the starting amides were demonstrated to influence the condensation process. Elemental iodine was used for the first time herein as an acid catalyst for the condensation of glyoxylic acid or its ester, which gave access to diaminoacetic acid derivatives in higher yields in most cases, as opposed to p-toluenesulfonic acid (PTSA). An abnormally high activity of mesyl amide when condensed with ethyl glyoxylate was noticed, which may evidence a special impact of the sulfonyl moiety in the amide molecule on the condensation.

Scholars from around the world have been attempting to simplify and cheapen the synthetic method for the promising high-energy compound CL-20 for decades. The lack of understanding of the formation mechanisms of hexaazaisowurtzitane derivatives―CL-20 precursors―is a barrier to solving the said problems. Here, we report the results from an in-depth study into the acid-catalyzed condensation between benzamide and glyoxal in a molar ratio of 2:1 in polar protic and aprotic solvents. Sixteen compounds were isolated and identified, of which eight were synthesized for the first time. A geminal diol, N,N’-(2,2-dihydroxyethane-1,1-diyl)dibenzamide, was synthesized. Two isomers of 1,2-bis(benzoylamino)-1,2-ethanediol were isolated and identified. N,N’-(1-oxoethane-1,2-diyl)dibenzamide and 2-oxo-2-[(phenylcarbonyl)amino]ethyl benzoate were produced that were likely formed due to the 1,2-hydride shift. N-polysubstituted 1,4-dioxane-2,3,5,6-tetramine was synthesized for the first time, whose structure may be of interest as a scaffold for new explosives. DMSO, THF and HCOOH were found to be able to engage in a reaction with benzamide, or condensation products thereof, and glyoxal under acid-catalyzed conditions.

The synthesis of substituted aza- and oxaazaisowurtzitanes via direct condensation is challenging. The selection of starting ammonia derivatives is very limited. The important step in developing alternative synthetic routes to these compounds is a detailed study on their formation process. Here, we explored an acid-catalyzed condensation between 4-tert-butyl-2,6-dimethylbenzenesulfonamide and glyoxal in aqueous H2SO4, aqueous acetonitrile and acetone, and established some new processes hindering the condensation. In particular, an irreversible rearrangement of the condensation intermediate was found to proceed and be accompanied by the 1,2-hydride shift and by the formation of symmetric disulfanes and sulfanes. It has been shown for the first time that aldehydes may act as a reducing agent when disulfanes are generated from aromatic sulfonamides, as is experimentally proved. The condensation between 4-tert-butyl-2,6-dimethylbenzenesulfonamide and formaldehyde resulted in 1,3,5-tris((4-(tert-butyl)-2,6-dimethylphenyl)sulfonyl)-1,3,5-triazinane. It was examined if diimine could be synthesized from 4-tert-butyl-2,6-dimethylbenzenesulfonamide and glyoxal by the most common synthetic procedures for structurally similar imines. It has been discovered for the first time that the Friedel–Crafts reaction takes place between sulfonamide and the aromatic compound. A new synthetic strategy has been suggested herein that can reduce the stages in the synthesis of in-demand organic compounds of symmetric and asymmetric aromatic sulfones via the Brønsted acid-catalyzed Friedel–Crafts reaction, starting from aromatic sulfonamides and arenes activated towards an electrophilic attack.

This study was focused on investigating the formation of N-polysulfonylsubstituted aza- and oxaazaisowurtzitanes via condensation of 4-dimethylaminobenzenesulfonamide with glyoxal and discovering new polyheterocyclic caged systems. More specifically, we explored how a donor substituent incorporated into the para position of the phenylsulfonamide molecule would influence the formation of cage products. Four new oxaazaisowurtzitane derivatives bearing one to three aza groups in the cage were consequently synthesized. A side reaction was found to take place, leading to a product having a non-isowurtzitane structure and four 4-dimethylaminobenzenesulfonyl moieties. The side product was analyzed by X-ray diffraction.

Three new functional 2-substituted 1,3-dinitroimidazolidines were synthesized herein. A synthetic strategy is suggested for structurally different alpha,alpha-dinitraminocarboxylic acids via condensation of glyoxylic acid ethyl ester with amine or amide derivatives. Alkali- and acid-catalyzed hydrolyses of ethyl 1,3-dinitroimidazolidine-2-carboxylate were studied. A series of hydrolysis products were isolated. The Curtius rearrangement of 1,3-dinitroimidazolidine-2-carboxylic acid to 2-isocyanato-1,3-dinitroimidazolidine was carried out. Hydrolyses of 1,3-dinitroimidazolidine-2-carbonyl azide and 2-isocyanato-1,3-dinitroimidazolidine were studied. 1,3-Dinitroimidazolidine-2-amine was captured as 1,3-bis(1,3-dinitroimidazolidin-2-yl)urea.

Three new functional 2-substituted 1,3-dinitroImidazolidines were synthesized herein. A synthetic strategy is suggested for structurally different α,α-dinitraminocarboxylic acids via condensation of glyoxylic acid ethyl ester with amine or amide derivatives. Alkali- and acid-catalyzed hydrolyses of ethyl 1,3-dinitro-1,3-diazacyclopentane-2-carboxylate were studied. A series of hydrolysis products were isolated. The Curtius rearrangement of 1,3-dinitroimidazolidine-2-carboxylic acid to 2-isocyanato-1,3-dinitroimidazolidine was carried out. Hydrolyses of 1,3-dinitroimidazolidine-2-carbonyl azide and 2-isocyanato-1,3-dinitroimidazolidine were studied. 1,3-Dinitroimidazolidine-2-amine was captured as 1,3-bis(1,3-dinitroimidazolidin-2-yl)urea.

By application of acid-catalyzed condensation of propane-2-, benzene- and methanesulfonamides with glyoxal a series of new derivatives of oxaazaisowurtzitanes were obtained, in particular, new heterocyclic systems: 2,4,6,8,12-pentaoxa-10-aza-and 2,4,8,12-tetraoxa-6,10-diazatetracyclo[5.5.0.0(3,11).0(5,9)]-dodecanes.

Methods for the preparation of various N -substituted oxaazaisowurtzitane derivatives have been generalized in this review. The advantages, drawbacks, and perspectives for the development of the main approaches to the synthesis of these compounds have been discussed. A comparison is provided for the physicochemical and explosive characteristics of energetic compounds containing the frameworks of oxaazaisowurtzitanes, CL-20, and HMX.

A condensation between mesylamide and glyoxal under highly acidic conditions was studied. A series of new compounds whose structures contain a moiety of oxaazatetracyclo[5.5.0.0(3,11).0(5,9)]dodecane were synthesized. The synthesis processes were optimized and main factors affecting the assembling of cage products were revealed. Assumptions are made regarding the formation mechanism of these chemical entities. For the first time, compounds have been obtained that include moieties of 2,6,8-trioxa-4,10,12-triazatetracyclo[5.5.0.0(3,11).0(5,9)]dodecane and 2,4,6-trioxa-8,10,12-triazatetracyclo[5.5.0.0(3,11).0(5,9)]dodecane. An X-ray diffraction analysis of the new compounds was performed.