21787-04-2

Upstream product

• 136-95-8 2-amino-benzthiazole 
• 123-06-8 Ethoxymethylenemalononitrile 
• 30006-84-9 N'-(benzo[d]thiazol-2-yl)-N,N-dimethylformamidine 
• 109-77-3 malononitrile 
• 16849-88-0 1-(dimethylamine)-2,2-dicyanoethylene 

Relevant academic research and scientific papers

Regioselectivity in the Reaction of 2-Aminobenzothiazoles and 2-Aminobenzimidazoles with Enaminonitriles and Enaminones: Synthesis of Functionally Substituted Pyrimido[2,1-b][1,3]benzothiazole and Pyrimido[1,2-a]benzimidazole Derivatives

A variety of new polyfunctionally substituted benzo[d]pyrimido[2,1-b][1,3]thiazole and benzo[4,5]imidazo[1,2-a]pyrimidine derivatives have been synthesized. The general synthetic procedure used for this purpose involves the condensation of 2-aminobenzothiazole and 2-aminobenzimidazole with a variety of enaminonitriles, enaminones, and acrylaldehyde. The regioselectivity for initial attack of either endocyclic ring nitrogen or exocyclic amino group was studied and rationalized for. It has been concluded that ring nitrogen is the most reactive cite in acidic medium, and cyclic intermediate can also be isolated, attesting to this conclusion upon cyclization. However, in basic or neutral medium, the exocyclic amino group was found to be the most reactive center. All structures of the newly synthesized compounds were elucidated by elemental analysis, spectral data, and alternative synthetic route whenever possible.

Nitrogen Bridgehead Compounds. 63. Ring-Chain Tautomerism of malonitriles

Twenty-one α-amino aza heterocycles were reacted with (ethoxymethylene)malonitrile.UV and 1H and 13C NMR studies indicated that in solution the structures of the condensation products can be described as chain and ring tautomers.Investigations were also made of the solvent and temperature dependence of the position of equilibrium of the ring and chain tautomer forms and the effect of protonation on the ring-chain tautomerism of the 2-aminopyridine derivative.The proportion of the ring form is increased by the presence of a substituent in position 2 of the pyridopyrimidine skeleton type ring tautomer and also by electron-donating substituents in position 7 or 8, while electron-accepting groups increase the content of the chain tautomer.A substituent in position 6 sterically favors the chain form, while substituent in position 9 influences the equilibrium between the ring and chain tautomer forms through its electronic and steric properties and its hydrogen bond forming ability.The 1-aminoisoquinoline derivative is present in ring form in both CDCl3 and Me2SO-d6.The derivatives of 2-aminoquinoline, 3-aminoisoquinoline, 2-aminopyrimidine, and 2-aminopyrazine predominantly exist as chain tautomers.The derivatives of ?-excess five-membered heterocycles - of 2-aminothiazole, 3-aminopyrazole, 2-aminobenzthiazole, and 2-aminobenzimidazoles - favor the ring form.In the case of 3-aminopyrazole, the chain and ring forms could be seperated.