Polyaza 𝛼-oxoketene 𝑆,𝑁-acetals can exist as either enamino or imino tautomeric forms. Based on the spectroscopic data and structural analysis of one of the 𝑆,𝑁-acetals, the stereochemistry was unambiguously assigned as an all-𝐸-configuration. The crystal structure confirms the enamino structure and shows extensive use of C-H…X (X = N, O, and S) weak hydrogen bonding interactions, thereby generating a 3-dimensional network in solid state.

A novel and facile one-pot synthesis of 1-substituted tetrahydro-Β-carbolines by cyclocondensationof ketene S,S–acetals with tryptamine in presence of In $Cl_{3}$ and TFA as co-catalysts by Bischler-Napieralskicyclization is described. The reaction involves formation of one C-N bond, one C-C bond and a new ringannulation over an indole moiety.

A novel and facile one-pot synthesis of 1-substituted tetrahydro-Β-carbolines by cyclocondensationof ketene S,S–acetals with tryptamine in presence of In $Cl_{3}$ and TFA as co-catalysts by Bischler-Napieralskicyclization is described. The reaction involves formation of one C-N bond, one C-C bond and a new ringannulation over an indole moiety.

An efficient and facile synthesis of spirooxindole derivatives bearing pyrano[2,3-c]pyrazole moiety has been achieved using deep eutectic solvent (DES) promoting a four-component reaction. The protocol avoids the use of costly and toxic catalysts and organic solvents which encounters many side effects on the environment and human beings. The simplicity and versatility of this eco-friendly green method isdescribed.