title: Azine-Hydrazone Tautomerism of Guanylhydrazones: Evidence for the Preference Toward the Azine Tautomer.
abstract: Guanylhydrazones have been known for a long time and have wide applications in organic synthesis, medicinal chemistry, and material science; however, little attention has been paid toward their electronic and structural properties. Quantum chemical analysis on several therapeutically important guanylhydrazones indicated that all of them prefer the azine tautomeric state (by about 3-12 kcal/mol). A set of simple and conjugated azines were designed using quantum chemical methods, whose tautomeric preference toward the azine tautomer is in the range of 3-8 kcal/mol. Twenty new azines were synthesized and isolated in their neutral state. Variable temperature NMR study suggests existence of the azine tautomer even at higher temperatures with no traces of the hydrazone tautomer. The crystal structures of two representative compounds confirmed that the title compounds prefer to exist in their azine tautomeric form.
authors: Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER) , Sector 67, S.A.S. Nagar 160 062, Punjab, India.
authors: Sumit S
authors: SS
authors: Chourasiya
authors: Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER) , Sector 67, S.A.S. Nagar 160 062, Punjab, India.
authors: Deepika
authors: D
authors: Kathuria
authors: Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER) , Sector 67, S.A.S. Nagar 160 062, Punjab, India.
authors: Sampada S
authors: SS
authors: Nikam
authors: Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER) , Sector 67, S.A.S. Nagar 160 062, Punjab, India.
authors: Ashok
authors: A
authors: Ramakrishnan
authors: Department of Chemical Sciences, Indian Institute of Science Education and Research , Mohali Sector 81, S.A.S. Nagar 140 306, Punjab, India.
authors: Sadhika
authors: S
authors: Khullar
authors: Department of Chemical Sciences, Indian Institute of Science Education and Research , Mohali Sector 81, S.A.S. Nagar 140 306, Punjab, India.
authors: Sanjay K
authors: SK
authors: Mandal
authors: Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER) , Sector 67, S.A.S. Nagar 160 062, Punjab, India.
authors: Asit K
authors: AK
authors: Chakraborti
authors: Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER) , Sector 67, S.A.S. Nagar 160 062, Punjab, India.
authors: Prasad V
authors: PV
authors: Bharatam