Despite the practical aim of the investigation, we made some mechanistic observations were made during the project. First, we observed that the reaction had a short exothermal period of ca 20-30 seconds (see Figure and video in SI). After this period the formation of a significant amount of (TMS)2O was observed as a separated layer ((TMS)2O is insoluble in DMF). However, the 1 H NMR monitoring of the reaction mixture after the exothermal period (in 3-5 min) did not show the signals of the final products. The signals observed at ca. 9.0 ppm slowly transformed to signals of final products within 24 h at rt. These signals could be assigned to the intermediate azomethines formed from aldehydes 5 and sulfamide 1. Therefore, we decided to obtain the corresponding azomethines from various aldehydes 5b,d,e and sulfamides 1, 2. Then we put the product into the reaction with "CH-acidic" counterparts. Unexpectedly, the literature did not properly describe the azometines type 12 (Scheme 3). Despite seventeen compounds referred in SciFinder, only three were described with corresponding spectral data, proving their structure . Thus, we could not use the published procedure for the synthesis of imines and tried to generate and isolate them in a DMF-TMSCl system. It was found that the formation of corresponding imines was strongly dependent on the aldehydes' structure. In the case of a donor aldehyde 5b the reaction gave the desired imine 12b in good yield, whereas when the case bromosubstituted ones 5d used the many side products with undefined structures (probably polymeric) was formed and target imine 12d was isolated in low yield. Shifting to the acceptor aldehyde 5e with NO2-group led to the low conversion with formation of a hardly separable mixture of imine 12e and the major 8-membered dimer 13e (like in a described for (EtO)2CHCH2CO2Et), see ref. 12). A similar picture was also observed when we used N-substituted sulfamides. In the case of a donor-substituted aldehyde azomethine is the major product. Otherwise, the reaction between the aldehyde 5e and Me-substituted sulfamide 2 led to the formation of the major 8-membered product 15e, which structure was confirmed by an X-ray study (Scheme 3). Having in our hand the pure imine 12b, the reaction with acetoacetic acid amide 4c in DMF -TMSCl system was performed. The process proceeded significantly clean and during 24 h the corresponding product 7cb was obtained in a high yield and purity without an exothermal effect at the beginning. The experiment proved that imines type 12 are intermediates of the investigated 3-component cyclization. Moreover, the above-mentioned behavior was in accordance with our previous results, where aldehydes bearing donor substituents gave better results in contrast with aldehydes having acceptor ones. The azomethine type 14b also reacted with corresponding CH-components affording the cyclic product type 9cb more smoothly in comparison with a 3-component option.